134. Comments: We have few issues with the analyzer accuracy or ability of existing reference methods to perform. The real place for improvement is with uncertainty of certified gases. Based on cost, the proposed changes are not justified. Is a 1 yr limit on gas tag values reasonable? Does data support the need for the proposed expiration lengths and requirements for recertification? Through my observations, I believe that an improved audit program for the gas manufacturers would provide better results than the proposed changes in the methods since we rely on them as standards. The EPA is not made aware of these problems, but we frequently observe them in the field when conducting relative accuracy test audits. ( 0039, 0042, 0043)

Response: We understand your concern with the uncertainty of certified gases. We are currently evaluating ways of auditing manufacturer= s gases. Through this effort, we hope to obtain sufficient data to update our current thinking on the matter. Until then, we must continue to rely on the specifications and expiration limits set forth in the Traceability Protocol.

135. Comment: The mid level gas range is too wide to demonstrate linearity of the system. Non linearity is typically worst near 50 percent of the calibration range, and this proposed change would allow using a gas that hides the non linearity. Why change the current 40 to 60 percent to the proposed 20 to 70 percent? It appears to provide less accurate data. The width of the proposed range is excessive and is so wide that the calibration curve may not accurately reflect instrument response. The old 40 to 60 percent is reasonable and should remain the standard. ( 0016, 0028, 0032, 0041, 0059)

Response: We have retained the 40 to 60 percent of calibration span range for the midlevel calibration gas.

136. Comment: Zero gas falls in the category of low level gas. Is the gas manufacturer required to certify the zero gas according to the Protocol? If so, the Protocol should include a procedure for zero gas. ( 0032)

Response: Where a zero gas is used for the low level gas, it does not have to be certified by the traceability protocol.

137. Comment: Is the term low level gas also a potential reference to zero gas? Can calibration gases still be generated by a Method 205 dilution system? Some test firms have invested largely in dilution systems. ( 0030)

Response: See the response to Comments 138. 48 3.12 NO2 Converter Efficiency Test in Method 7E 138. Comment: NO2 calibration gases for the converter test are not available as EPA Traceability Protocol for Assay and Certification of Gaseous Standards. Since these gases are not available, this section cannot be completed to meet the standards in Section 7.1. NO2 gas exhibits unusual storability problems and maintaining an NO2 calibration gas at its= certified concentration may be difficult. ( 0008, 0010, 0038)

Response: We have found that NO2 of traceability protocol quality is available commercially, but in limited concentrations from limited sources. We also concur that there may be long term stability problems with NO2 cylinder gases. Because of these concerns, we have retained the original procedures cited in Method 20 for determining converter efficiency in addition to this procedure of direct evaluation with NO2. The NO2 approach is simple, quick, and provides a direct assessment of the converter efficiency from the known cylinder tag value. However, although this approach is theoretically acceptable and straight forward, we have cautioned the user that state of the art NO2 calibration gases may not be sufficiently stable and thus make it more difficult to pass the 90 percent conversion efficiency requirement. In cases where this option is taken, the NO2 must be prepared according to the traceability protocol and be accurate within 2 percent.

139. Comment: For the converter efficiency gases in Section 7.1.4, NO2 calibration gases are not available as an EPA Traceability Protocol for Assay and Certification of Gaseous Standards. Since NO2 protocol gases are not available, this section could not be completed per the standards required in Section 7.1. ( 0042)

Response: See response to Comment 138.

140. Comment: The preamble, section II, item 6 states to perform converter check before each test, but this conflicts with the Summary Table, which says after each test. ( 0025)

Response: The converter check must be passed before each test; this has been clarified.

141. Comment: The methodology for implementing a NOx converter correction factor based on the converter test results is unclear. While requiring this test is preferred, maintaining the current methodology for correcting for system bias eliminates the need for any additional corrections. ( 0038)

Response: Correcting the test results for converter efficiency is not required in the final rule but may be done at the discretion of the tester. We have provided an equation for this purpose where desired when the alternative Tedlar bag converter check is used.

142. Comment: What happened to the current method of mixing air and NO to generate NO2 for the converter check? There are several practical problems with using NO2 cylinders in the proper ranges for every test. ( 0004, 0009) 49 Response: The current method of mixing air and NO to generate NO2 for the converter check was retained as an allowable option.

143. Comment: The requirement for the uncertainty of the NO2 cylinder concentration is missing, and should be listed as 2 percent. ( 0013)

Response: The uncertainty of the NO2 cylinder concentration must be within 2 percent, and this has been noted.

144. Comment: Method 7E section requires that the converter efficiency gas have a concentration within 50 percent of the measured concentration. In most cases, the tester has no means to determine the NO2 concentration in advance so there is no viable means to comply with this specification. It is also impractical to carry several NO2 cylinders to be properly prepared. Some comments suggest a simple daily check of the converter is the practical and reasonable approach. Some comments say this section conflicts with Section 8.2.3 or 8.2.4, and, furthermore, uses the term suggest rather than must. What does within 50 percent mean? Especially clarify vs. 50 150 percent suggested in Section 8.2.4. Since we do not know the NOx analyzer range at which we will be operating, it could be specified that the NO2 converter check be done at a specified percentage of the range on which the analyzer will be operated. Perhaps require using a gas concentration equal to or greater than the highest NO2 concentration that will be measured. Comment cites NIST stability problems with NO2, and suggests EPA= s Alt 013 method for using 50 ppmv NO2 gas as a one size fits all approach if it is necessary to retain use of NO2 gas at all. A converter efficiency test can be demonstrated with any NO2 gas, such as 20 ppm, relevant to a specific source category. ( 0004, 0011, 0012, 0013, 0014, 0016, 0022, 0027, 0029, 0028, 0031, 0031, 0032, 0034, 0035, 0038, 0039, 0047)

Response: We understand the difficulty in preparing NO2 cylinder gases to match anticipated emission levels. We have dropped the proposed requirement to match the stack NO2 concentration within 50 percent and have added a 40 to 60 ppm test concentration for all cases as is allowed in our Alt 013 method.

145. Comment: If the NO2 concentration is low, as it usually is (< 5 ppm), the " 50 percent of the average measured concentration will be very difficult to meet. Therefore, an alternative specification of " 10 ppm ( or perhaps 20 ppm) should be provided. In addition, if the NO2 is significantly variable, the " 50 percent of the average measured concentration will be too restrictive. For these sources, there should be an alternative specification, e. g., > 150 percent of average. In all cases, dilution of the NO2 standard should be allowed ( 0032, 0030, 0031).

Response: See response to Comment 144.

146. Comment: Note that NO2 is a gas that must be handled with extreme care even at low concentrations because of exposure effects. Do the proposed changes produce an increase in data quality that justifies the burdens of the procedure? Since most converters have a definite lifespan, would it be possible to evaluate it on a less frequent basis based on operational life and NOx concentrations in the effluent? Is it acceptable to both the Office of Air Quality Planning and 50 Standards ( OAQPS) and the Clean Air Markets Division ( CAMD) to produce the required concentrations of NO2 from protocol cylinders using Method 205? ( 0059)

Response: We have noted in the safety section that NO2 is a toxic and dangerous gas. We are allowing this procedure at the discretion of the tester because it is simple, quick, and provides an accurate assessment of the converter efficiency from the known cylinder concentration. We believe a converter test before each source test is a better way to assure converter efficiency than by scheduling evaluations whenever projected life spans and exposure concentrations suggest the need. The new requirement to test the converter at 40 to 60 ppm should eliminate the need for gas dilution. Gas dilution meeting the Method 205 criteria is acceptable to OAQPS, but for part 75 applications, Administrative approval from CAMD is required.

147. Comments: Why was the current converter efficiency method ( as described in Method 20, using a Tedlar bag with NO and O2 mixture for 30 minutes) removed from the rule? We recommend allowing the current method as well as the NO2 calibration gas method. ( 0009, 0020, 0027, 0031)

Response: The converter efficiency method currently in Method 7E has been retained as an additional option.

148. Comments: The NO2 to NO converter check outlined in 40 CFR 86.123 78 says you can perform it prior to service and at least monthly thereafter, while the Summary Table of QA/ QC says after every test. Please clarify, and note the increased cost if it is the latter. Please clarify what prior to the test means. It can be interpreted as each test, 1 day, 7 days, 30 days, or before each project. Before each test is too excessive. NO2 is an unstable, expensive gas with a short shelf life, so before each test is excessive and should be quarterly or bi annually. Note that stainless steel converters have endless life, unlike the Molly converters which may require more stringent checks. ( 0014, 0020, 0034, 0035, 0043, 0048, 0056)

Response: The converter efficiency must be verified prior to each source test whether you use the NO2 cylinder gas test, the NO and O2 in the Tedlar bag procedure cited in Method 20, or the procedure in 40 CFR 86.123 78. We do not believe this is excessive. Other less frequent alternative procedures may be used with the approval of the Administrator.

149. Comment: What about the cases where the amount of NO2 is low in comparison to NO? Perhaps a fixed value of NO2 could be specified based on impact. In some cases, the principal component is NO2 ( as in some combustion turbines with CO catalyst); 90 percent efficiency means that the measured concentration would be 10 percent low. If the NO2 component is 5 percent of the total, then 90 percent efficiency would mean that the measured concentration is 0.45 percent low ( 0032).

Response: The allowance currently in Method 7E for a converter exemption in cases where the NO2 portion of NOx is less than 5 percent provides opportunity for a low data bias. We have not included the converter exemption allowance in Method 7E to improve the certainty of the generated data. 51 150. Comments: How can a tester determine what the amount of NO2 is in the sample if the analyzer does not differentiate between NO and NO2? ( 0009, 0031)

Response: The proposed requirement to conduct the converter test at an NO2 concentration within 50 percent of the emission NO2 concentration has been dropped. A new requirement to evaluate the converter in the 40 to 50 ppm range has been added.

151. Comment: NO2 cylinders are more unstable than the Tedlar bag technique. In my experience, NO2 cylinders are fairly accurate for up to 1 month, then continue to degrade, and I have checked this on multiple analyzers, so it is not a converter issue. The comment then presents a modified Method 20 bag technique to determine true converter efficiency, because the author assumes the lack of this procedure is why the bag technique was discarded. ( 0031, 0039)

Response: See response to Comment 138. The modifications to the Method 20 bag procedure that the commenter recommends have been incorporated into Method 7E.

152. Comment: The uncertainty calculation does not adjust for NO2 converter efficiency. Some instruments do, and that is what it should say here. ( 0035)

Response: We have dropped the proposed requirement to calculate and report the uncertainty of each test run.

153. Comment: Using actual NO2 cal gas to determine conversion efficiency removes any question of the NO to NO2 conversion as per the old Tedlar bag method; we think this is a good choice. We suggest retaining the stability requirements in the current Method 20, Section 5.6.1, along with the > 90 percent conversion efficiency requirement for an acceptable system. ( 0041)

Response: We have retained the 90 percent converter efficiency and 30 minute stability requirement.

154. Comment: This section says that converter efficiency gas must have a NO2 concentration within 50 percent of the average. Is this referring to the measured concentration of NOx or NO2? To be consistent with Section 7.1.4, this should be NO2. ( 0038)

Response: The proposed requirement to evaluate the converter within 50 percent of the NO2 concentration in the source has been dropped. The new converter test requires an NO2 concentration between 40 to 60 ppm if this option of evaluating the converter is chosen.

155. Comment: For the converter efficiency gas, it is impractical to have an NO2 calibration gas cylinder that is within 50 percent for every measured NO2 concentration. This will require contractors to carry many NO2 calibration gas cylinders. How would one know what the NO2 concentration is if reported emissions are for NOx? What portion is NO and what is NO2? A daily check of the converter with a cylinder of 50 ppm NO2 is practical and reasonable. The converter should demonstrate greater than 90 percent conversion of NO2 to NO. 52 Additional gases will significantly affect testing costs. Another cost may be associated with DOT requirements for commercial vehicles and hazardous material transport. Any time additional gases can be eliminated from a test program, this should be considered. ( 0009, 0011, 0056)

Response: We agree with the commenter and have incorporated the recommendations. The proposed converter test using NO2 cylinder gas is now one of three options we allow for the efficiency test. The original Tedlar bag test option and a similar procedure cited in 40 CFR 86.123 are testing options as well.

156. Comment: In Section 10.1 of Method 7E, the 3rd sentence states if your analyzer measures NO and NO2 separately, then you must use both NO and NO2 calibration gases. Please clarify and give examples of which analyzers would be covered here... in my opinion it would be most of them. For example, in my opinion a chemiluminescence analyzer measures NO and NO2 separately. Does this mean I now have to calibrate with three NO and three NO2 gases? Most NOx analyzers could measure both NO and NO2 by making total NOx and NO measurements separately. Make it clear that analyzers using NOx converters do not fall into the separate measurement category. ( 0014, 0038)

Response: Clarity has been added to Section 10.1 to state that the analyzer must be calibrated for all species of NOx that it detects. Since the chemiluminescence analyzer only detects NO, it only has to be calibrated with NO. This has been specifically stated.

157. Comment: There should be an exemption for low level NO2 emitters because determining the 90 percent converter efficiency is not reasonable or practical for such sources ( 0032).

Response: The proposed requirement to evaluate the converter within 50 percent of the NO2 concentration in the source has been dropped. The new requirement to evaluate the converter in the 40 to 60 ppm range is practical for low level NO2 emitters and no exemption is needed.

158. Comment: For the converter efficiency in Section 3.4, what happened to the current method of mixing air and NO? Does this mean that for every test we have to carry a cylinder of NO2 so that we can conduct a converter efficiency test for every concentration and still use the equations for upper and lower uncertainty? It appears that the use of an NO2 calibration standard is required. NO2 gas exhibits unusual storability difficulties. Maintaining an NO2 calibration gas at its certified concentration could be difficult. ( 0004, 0010)

Response: See response to Comments 138, 148, and 150.

159. Comment: For the converter efficiency gas in Section 7.1.4, how do we know what the measured NO2 concentration is? ( 0004)

Response: See response to Comment 155. 53 3.13 General Comments 3.13.1 Supportive Comments 160. Comment: ( 1) Bringing consistency to the methods will bring clarity and remove a great deal of confusion. Standardizing 6C or 7E is a good idea, since the precision and repeatability of those methods has been demonstrated by an EPA study. ( 2) Removal of the drift requirement will simplify testing and should be acceptable as long as the system passes initial and final bias tests. ( 3) The NO2 system bias and NH3 interference problems found at low concentrations are best evaluated using dynamic spiking. ( 4) The 30 sec minimum response time requirement was always difficult to meet and never necessary. ( 0016)

Response: Of the noted revisions the commenter thought were a good idea, only the calibration drift requirement between samples has been retained because of its expressed need by other commenters.

161. Comment: Overall, the proposed revisions are positive improvements to the test methods and are expected to be much easier to follow by individuals conducting air emission stack tests. ( 0024)

Response: No response is necessary.

162. Comment: We compliment EPA on their very credible performance in addressing a complex subject, and revising it into a well harmonized, simplified, and updated test methods that allow for flexibility and innovation in the emissions measurement industry. We compliment the EPA staff at OAQPS/ EMC for developing a well thought out rule that encourages a system of testing performance for instruments and sampling systems. ( 0053)

Response: No response is necessary.

163. Comment: This proposal addresses long standing inconsistencies between instrumental test methods. The revised methods provide a standard approach for defining a confidence range around the method result which will aid in assessing compliance. The previous procedures generated a single value with no explicit estimate of uncertainty which created a level of certainty that is not warranted by the technology of the methods. This new approach is particularly useful when measuring very low emission levels, such as NOx emissions from gas turbines with selective catalytic reduction control equipment. These are very positive changes. ( 0060)

Response: No response is necessary.

164. Comment: It is obvious that the editors put a great deal of time and effort into the preparation of this proposal, and they should be commended for their dedication. ( 0059)

Response: No response necessary. 54 3.13.2 Adverse Comments 165. Comment: The proposed changes are intended to harmonize, simplify, and update the test methods, but they do not accomplish this goal. The revised methods are conflicting, contain numerous errors, misstatements, and inconsistencies. Some of the requirements are so confusing and lack proper explanation that we could not determine how to conduct those test requirements. Other requirements appear to be impossible to meet, and we do not believe we could perform these reference method tests as described in the proposed procedure. Further, I do not see how the proposed changes either simplify or reduce the costs of testing. The proposed rules may simplify the way the methods are written, in that they all refer to 7E, but they increase the complexity of the field procedures rather than simplifying them. The proposed rules will make the source testing profession more difficult, with the result being less experienced people generating worse data than is presently obtained. ( 0008, 0009, 0014, 0027, 0031, 0032, 0033, 0034, 0039, 0041, 0042, 0043, 0055)

Response: We disagree that the updates do not improve the methods or the data generated. In the final rule, we attempted to correct any errors and inconsistencies that were brought to our attention through the public comments on the proposal.

166. Comment: Some of the proposed changes are anticipated to impact the length and cost of RATA and/ or stratification tests and result in additional cal gases being ordered and maintained for testing. ( 0042)

Response: We disagree that we lengthened and increased the cost of RATA because we specifically allow for performance testing of CEMS ( i. e., RATA) using procedures in the appropriate performance specification or applicable regulation. See Section 8.1.1. Secondly, we added flexibility by including alternative procedures that may save the tester time when applied in appropriate cases. Finally, we allow Method 205 for diluting high concentration calibration gases of traceability protocol quality. Any additional costs associated with purchasing additional calibration gases is offset by the increase in data certainty.

167. Comment: Almost all third party testing companies are small, and much of the available talent resides in these small companies. These companies cannot afford the equipment with recorded alarms and superfluous flow controllers that larger companies have but rely on knowledge, experience, and finesse. The proposed rules have many direct quotes and ideas from a set of comments presented to EPA in draft form by and industry trade group, which is a group that manufactures air pollution control equipment, instrumentation, stack testing equipment and CEMS. While this group is an important technical resource, it is also clear that they only stand to gain from this legislation and have nothing to lose. Some of the trade group comments are reasonable, but others are self serving. The EPA has proposed a number of quality assurance requirements which are unreasonable, unnecessary, and more stringent on the tester than the analyzer and calibration gas manufacturers. ( 0039)

Response: The EPA received input from a number of stakeholders including industry groups, gas and instrument manufacturers, stack testers, and regulators prior to the proposal. Valuable input was obtained, and we tried to keep the method revisions neutral and not favor a 55 particular group. Acceptable performance criteria for tests are based on what is necessary for acceptable results, whereas acceptable performance criteria for manufacturers are based on producing a quality instrument. We continue to rely on testers= knowledge and experience to select and use appropriate equipment at individual facilities.

3.13.3 Other Comments 168. Comment: We support the goal of addressing low concentration measurements. However, these revisions provide little to enhance those measurements. In addition, the special provisions for sampling system bias performance criteria for measuring low concentrations of exhaust species include a 3 yr sunset clause. EPA should eliminate the sunset clause, identify issues associated with low concentration measurement, and identify additional measures to address those issues. ( 0032)

Response: The Agency has tried, within its resources, to identify the issues associated with low concentration measurements. We have consulted with instrument manufacturers and cylinder gas producers to determine the reasonable capabilities of current measurement technology. There is still much work to be done to adapt current test methods to the demands of low Bconcentration measurements; however, we feel the method additions that were proposed are a step in the right direction. Note that we have dropped the proposed 3 year Asunset clause@ on the alternative specifications. However, we reserve the right to revise them as more data become available.

169. Comment: For concentrations less than10 ppm, EPA proposes a bias specification of 0.5 ppm, which makes QA specifications practically meaningless for many low concentration measurements. Problems with low concentration measurements have been discussed in public forums for at least 10 years now. Some investigative work has been done by groups outside of EPA, but it has not been enough, largely due to funding constraints. EPA should conduct a study focusing on low concentration CO and NOx issues: ( 1) Stability and accuracy of calibration gases; ( 2) achievable calibration error and bias specifications; ( 3) effects of ammonia in sample gas; ( 4) significance of NO2 sampling system bias; and ( 5) cross interference from compounds other than analytes. ( 0016)

Response: The proposed alternative bias specification of 0.5 ppm has been retained, but we have dropped the proposed three year sunset provision. The Agency does not currently have funds to perform the study suggested by the commenter.

170. Comment: The test methods should include a discussion of measurement sensitivity, minimum detection limit ( MDL), and practical quantification limit ( PQL). These important issues are at the forefront of critical problems associated with emissions testing. EPA should address these topics during this revision to the test methods to clarify the definition of MDL and PQL and provide appropriate procedures to determine these parameters for emissions tests with results that challenge instrument sensitivity. ( 0032) 56 Response: These recommendations are a good idea but beyond the scope of this rulemaking since we have not fully assessed the methods relative to establishing MDLs and PQLs.

171. Comment: The EPA proposes to revise Section 1.2 of the methods to state that they are required in " specific New Source Performance Standards, Clean Air Marketing Rules, and State Implementation Plans and Permits where measuring [ the applicable parameter] in stationary source emissions is required." This statement could be misinterpreted to say that the methods are required in each of those regulatory programs whenever such measurements are required. That is clearly not the case. Each method applies when a specific permit or regulation requires its use. The programs EPA cites may very well be examples of programs where regulations may specify ( or allow) the use of these methods, but they do not necessarily require these methods. Other methods, including the non instrumental test methods, or some alternative method, may be allowed. EPA should abandon the proposed revision to the applicability sections and retain the existing language, which states that: AThis method is applicable to the determination of [ the applicable parameter] in emissions from stationary sources only when specified within the regulations.@ If the EPA wants to name specific programs where use of these methods might be required or allowed, they should list them as examples and not as statements of applicability. Applicability of particular test methods even within Part 60 is addressed in the individual NSPS subparts, not in the test methods themselves. ( 0038)

Response: Section 1.2 was modified to mention the programs as examples of where the methods may be required.

172. Comment: Since major national emission reduction efforts such as the Acid Rain and NOx Budget programs rely on 40 CFR Part 75 emission monitoring accuracy calculations, we request that EPA= s Emissions Measurement Center consult with the Clean Air Markets Division as to what possible effects the proposed changes could have on calculated accuracy and on a facilities= ability to pass RATAs. ( 0016, 0025, 0038, 0042)

Response: The Clean Air Markets Division is and has been a component of the internal review team.

173. Comments: Method 25A is considered an instrumental method and should have been included with this package for consistency. Methods 3A, 6C, and 7E should be used as the foundation, and Methods 10, 20, and 25A should be revised to match this format. Most state agencies currently allow Method 10 to be performed by the procedures of Method 6C as long as a 4 pt calibration is performed ( zero, low, mid and high). Similarly, most state agencies allow or specify Method 20 to be performed as per 7E while following sample collection procedures of Method 20. For 25A... it is a matter of correcting out bias according to 6C procedures. The hotwet nature of 25A should be preserved, but cal gas ranges, QA parameters, etc., should be made consistent with the other methods. In addition, I recommend and option in 25A for methane and/ or ethane analysis by one of the Method 18 techniques for subtraction from the 25A result. Some of the newer analyzers, such as the VIG, TECO, and California Analytical non methane analyzers, should be included as an alternative in the procedure. Other alternatives would be bag sampling with lab analysis or on site GC with direct interface. See original comment for further 57 details of the suggestion. Once a final, uniform methodology can be agreed upon and approved, the 7E procedure should also be incorporated by reference into Method 25A. ( 0017, 0021, 0034, 0038, 0039, 0043)

Response: We agree that Method 25A should be updated to incorporate the revisions made to Method 7E. We plan to do this in a separate, future rulemaking.

174. Comments: How will the proposed changes affect Performance Specifications 2, 3, and 4? ( 0021)

Response: The changes will not affect the procedures and requirements in the applicable performance specifications. The sampling points prescribed in the performance specifications will govern when the instrumental methods are used in relative accuracy testing.

175. Comment: Maintenance logs for all equipment should be required to be maintained and available in the field for inspection. These logs should have entries that are dated and initialed and include records of maintenance, parts replacement, problems reports, corrective actions taken and other relevant information. ( 0022, 0023)

Response: This is a good suggestion which should already be an integral part of a tester= s standard operating procedure. However, to keep the updates as minimal and simple as possible, we prefer the keeping of maintenance logs be a part of the testing company= s QA/ QC and not a part of the methods.

176. Comments: The preamble states that the manufacturer= s stability test ( MST) is required for all instruments used routinely for low concentrations, but the statement is not made in the text of any of the methods. It should be stated clearly in the Summary Table for QA/ QC of 7E, Section 9, and in 7E, Section 16.2. Further, the Summary Table indicates that the MST is mandatory for all analyzers, but the preamble only mentions low emitters, so which is it? ( 0025)

Response: It is now stated in Method 7E that the MST is required for all instruments used routinely for low concentration measurements, and is cited in the other methods. The summary QA/ QC table in Section 9 of Method 7E was corrected to require it only in the case of routine low concentration measurements.

177. Comments: There is a discussion of type certification in Method 6C, but none for 7E. Is this an oversight? ( 0025)

Response: The manufacturer= s stability test is offered as an option in Method 3A, 6C, 7E, 10, and 20 and is a requirement in each method where routine low concentration measurements are made.

178. Comments: The commenter suggests that we remove Section 12.7.5 ANOx Emission Rate Concentration@ from Method 7E and include it in Method 19. Method 7E can then reference Method 19. ( 0034) 58 Response: We agree with the commenter and removed Section 12.7.5 from Method 7E.

179. Comments: Why are Methods 3A, 6C, and 10 abbreviated? There is a great deal of confusion, over specification and under specification that occurs with this cost saving.??????? In the long run, it will be cheaper to have each method stand alone with each section having been carefully thought out for that method/ instrument. The interference check of 6C is a prime example. ( 0035)

Response: We agree that specifying all the requirements in each method is clearer than abbreviating ( i. e. cross referencing). However, due to cost constraints, cross referencing is necessary.

180. Comments: Several of the proposed changes will impact the current RATA software developed around the existing reference methods. Changes will be costly and will require time to identify, re design, and test. Specific areas include ( 1) elimination of the drift test; ( 2) bias based on emission standard rather than span; ( 3) use of mid or high level gas for bias test; ( 4) low level gas required to be within 0.25 percent of upper range. ( 0042)

Response: The final rule: ( 1) retains the drift test and correction; ( 2) retains the requirement to calculate bias as a percent of span; ( 3) retains the requirement to use the mid or high level gas for bias checks; and ( 4) specifies that the low level calibration gas must be less than 20 percent of the calibration span, except where the low level gas is a zero gas. In that case, the specification is 0.25 percent of the calibration span or 0.5 ppm, whichever is less restrictive.

We understand that some of the updated specifications may require the adjustment of testing software now in use. We believe the benefits gained from using harmonized methods outweigh this initial inconvenience.

181. Comment: The term system calibration seems wrong. Don= t you mean system bias? We don= t calibrate a system. ( 0048)

Response: You have a point. We have added definitions for Asystem calibration mode@ and Adirect calibration mode@ to alleviate confusion. We prefer these simplified terms over the current wording to A introduce calibration gas at the calibration valve installed at the outlet of the sampling probe@ and Aintroduce calibration gas to the measurement system at any point upstream of the gas analyzer.@

182. Comments: The methods should state that, in the event the tester= s data acquisition and handling system malfunction or otherwise are not capable of providing certain data, hand written data are acceptable. ( 0038)

Response: This is already allowed in Section 6.1.9 of Method 7E.

183. Comment: The 40 CFR Part 60 Appendix A test methods that were revised in the 1997 proposal should be updated to include more current technology while not making the tests more restrictive. The current acceptance criteria prescribed by the calibration error, calibration 59 drift, bias and/ or interference check for Methods 3A, 6C, and 7E should not be changed in the proposal. Method 10 should be modified to require the same performance specifications as Methods 3A, 6C, and 7E. Method 25 should be modified to allow direct sample interface with the newer methane/ nonmethane analyzers available from gas analyzer manufacturers. Method 25 should also be modified to have fixed performance specifications for the analyzer/ sample interface similar to Methods 3A, 6C, 7E, and 10. ( IV D 03)

Response: In the October, 2003 reproposal, the methods were written to allow more current technology to be used. The acceptance criteria prescribed in the 1997 proposal for calibration error, calibration drift, and bias has been changed to conform with the current limits. Method 10 is being modified to require the same performance specification as Methods 3A, 6C, and 7E. Revisions to Method 25 will have to be made under a separate rulemaking since it is not a continuous instrumental test method. Such revisions are beyond the scope of this rulemaking.

184. Comment: Regardless of the data recording device, it should be mandatory that the calibration error, converter efficiency, stratification, and bias checks results be recorded along with the sample run data and copies of all data be included in the report. Having a hard copy of all these values will enable agency personnel to perform a thorough data validation of the values. ( 0011)

Response: The final rule requires that this data be documented and included in the report.

185. Comment: In the nomenclature, specifically Cdir and Cs, both state AYreported by the gas analyzer.@ To be consistent, this should say AYreported by the data recorder.@ These values for determining emissions are taken from the data recorder. Since the data from the data recorder will be used for emission calculations, then all other recorded values used in the emission calculations should be consistent and come from the data recorder. ( 0011)

Response: Cdir and Cs are revised in the final rule.

186. Comment: Lime kilns should be added to the Table 1, Entities Potentially Affected by this Action in the preamble. ( 0007)

Response: Lime kilns are added to the final rule preamble.

187. Comment: Uniform procedures should be prescribed for the determination of analyzer span. For example, reference method analyzer span could be selected such that the pollutant gas concentration encountered is not less than 30 percent of the analyzer range. This guideline is currently enforced by the Pennsylvania Department of Environmental Protection. Also, if Methods 6C, 7E, and 10 pollutant gas concentrations are less than 100 ppmv, reference method analyzer span cannot exceed 100 ppmv. This would establish an upper limit in which pollutant concentrations are non detect ( for example, SO2 emissions from a low odor recovery furnace). ( 0021)

Response: We believe that our revised definition of span and the requirement for the majority of the data to be between 20 and 80 percent of span address the commenter= s concerns. 60 188. Comment: EPA should consider a style similar to 25A, which evaluates ( 1) the entire system accuracy ( analyzer error and system bias) at the same time; ( 2) calibration limits of 5 percent of gas value; ( 3) span level at 1.5 to 2.5 expected emission concentrations; ( 4) four calibration gases at zero, low, mid, and high level; ( 5) bias/ drift conducted with low and midlevel gases. ( 0041)

Response: The requirement to perform separate analyzer calibration error and bias checks has been retained ( except for dilution type systems), with the low level gas and either the mid or high level gas used for the bias checks. The methods also continue to require the use of three calibration gases at low, mid, and high levels. We believe our revised span definition provides more flexibility than the approach advocated by the commenter.

189. Comment: For all methods, Section 1.2 ( applicability) should clearly state that the methods apply to periodic monitoring and exclude CEMS installed and operated according to Parts 60 and 75. There are not existing CEMS that could meet all of the proposed requirements in the methods. ( 0041)

Response: Since the subject methods are reference methods, the requirements would not apply to CEMS.

190. Comment: I agree that the proposal would advance the science of source testing, but I question whether the benefits to public health are sufficient to justify the increased costs. Data quality is unimportant if it doesn= t improve public health. Please don= t adopt the proposed rules without further revisions and opportunities to comment. ( 0043)

Response: We have made significant revisions to the methods as a result of voluminous comments and don= t believe that a re proposal is necessary.

191. Comment: Determining emission rates can be a challenge in a large exhaust stack. An approach used by some in the industry is to determine the average concentration of the emissions, then calculate the emission rate based on the fuel flow rate and the calculated emission factor ( or alternatively, the emission index). This approach should always be recommended as a tool for assuring data quality in determining mass emission rates. ( 0010)

Response: This approach may be helpful and recommended in a number of cases. However, we are limiting the method revisions to the determination of emissions on a concentration basis.

192. Comment: The ASME and SAE have both developed procedures for measuring emissions from gas turbines. SAE= s ARP 1256A is a common tool used in the aircraft engine industry, and ASME= s B133.9 1994 " Measurement of Exhaust Emissions from Stationary Gas Turbines" is also an excellent reference on methods for measuring gas turbine emissions. These methods should be codified as alternate measurement procedures, or as procedures for quality assurance. ( 0010) 61 Response: We were not forwarded copies of the noted methods to evaluate their requirements relative to Method 7E. Unless these methods satisfy the requirements of Method 7E, permission to use them must be granted by the Agency on a case by case basis.

3.14 Specific Comments on Method 3A Section 1.0 Scope and Application 193. Comment: Method 3A and Method 3B should be listed as appropriate method to determine diluent O2 or CO2 measurements necessary to convert emissions to units of the standard. ( 0032)

Response: The appropriate method for determining the diluent O2 and CO2 measurements necessary to convert emissions to units of the standard are better specified in the applicable regulation than the NOx measurement method.

Section 3.1 Definitions 194. Comment: Definitions for direct calibration, system calibration, range, and span are missing. ( 0013)

Response: We incorporated definitions for these terms by referring to Method 7E.

195. Comment: Delete high level gas, mid level gas, and low level gas ( they are not found in Section 3.0) from the list of definitions. ( 0013)

Response: We made sure that the Method 3A definitions refer to the appropriate Method 7E section( s).

196. Comment: Change Asampling system@ to Ameasurement <EMAIL_ADDRESS>( 0013)

Response: We agree that Asampling system@ is redundant with Ameasurement system@ and deleted it from the final rule.

Section 4.0 Interferences [ Reserved]

197. Comment: This section is reserved; yet extensive resources are required to conduct interference checks of O2 analyzers. Potential documented interferences should be discussed in this section and methods for eliminating or minimizing the effects should be included. ( 0032)

Response: We are unaware of potential interferences other than those currently cited in Method 3A and determining these interferences is beyond the scope of this rulemaking.

Section 6.1 Equipment and Supplies 62 198. Comment: This section adopts numerous equipment requirements from Method 7E that are entirely inappropriate for measurement of O2 and CO2 concentrations. For example, the proposed revisions to Method 3A reference the requirements of Method 7E Section 6.1.3 which explicitly requires that sample lines be fabricated of stainless steel or Teflon. Oxygen and CO2 are non reactive gases present at percentage levels and many other much less expensive materials are perfectly fine for use in sample lines and are commonly used in practice. Other inappropriate requirements referenced by the proposed revisions are associated with the requirements to heat the sampling probe, sample transport lines and other components of the sampling system. In many cases these provisions are not necessary when only diluent concentrations are needed to be measured for a specific test program. ( 0032)

Response: We agree and have added " as applicable" to the equipment specifications in Section 6.1 of Method 3A.

199. Comment: For wet based systems ( i. e., dilution or hot wet extractive), moisture removal systems and heated sample lines are neither performed nor essential. In stack dilution probes may not need a heated sample line, depending on the dew point of the sample. Dry based extractive systems may use a combined sample probe/ moisture removal system, after which an unheated sample line may be used, depending on the dew point. ( 0009, 0010, 0043, 0059)

Response: We agree. See response to Comment 198.

200 Comment: It seems like a modified M5 box with hot probe, filter, and moisture removal system hung from a rail could work for a traversing gas sampling system, which would not be allowable with your proposed heated line requirement. The heated line should not be a requirement. ( 0043)

Response: A modified Method 5 box with hot probe, filter, and moisture removal system is allowed. We removed reference to specifications for essential components in Section 6. This would facilitate the use of the modified Method 5 sampling, transport, and conditioning system you described.

201. Comment: In addition to the above, if only O2 and CO2 are measured, then there is no reason why you even need to prevent condensation, since these gases are not water soluble and would not be affected by any condensation formed upstream of the moisture removal system. ( 0011, 0048, 0059)

Response: See response to Comment 198.

202. Comment: Add AWhat do I need for the measurement system?@ before the first sentence. ( 0013)

Response: This statement was added. 63 203. Comment: What is the difference between flow control/ gas manifold and sample gas manifold? If the method requires constant sample flow, then a flow control should definitely be there. ( 0043)

Response: We replaced the term Aflow control/ gas manifold A with Acalibration gas manifold@ to distinguish it from the sampling manifold.

204. Comment: We suggest that you call 6.1 ASample Collection and Transport@ and 6.2 AAnalyzer and Data Recorder.@ It seems the Adata recorder@ is out of place in Section 6.1. ( 0043)

Response: The commenter provides a good suggestion; however, we are removing reference to specifications for essential components in Section 6 as noted in previous responses.

Section 7.1 Calibration Gas 205. Comment: The proposed revisions to Method 3A fail to explicitly require use of low level O2 mixtures rather than zero gas for O2 analyzers that should not use zero gas such as the very commonly used zirconium oxide analyzers. Use of zero gas for these types of analyzers, or any other measurement system that has a logarithmic output relative to concentration, will provide a false and misleading response. This false response will generally indicate stable operation even if the analyzer is calibrated or operating incorrectly. Note that the existing Method 3A specifies the use of a low range gas, having an oxygen concentration of less than 10 percent of the measurement range. ( 0032)

Response: The statement in old Method 3A says that a non zero gas may be used for an O2 analyzer that cannot analyze zero gas. But it does not specify which type( s) of analyzers have this issue. Therefore, the statement has not been included in the final rule. It is the responsibility of the tester to know which types of analyzers are not capable of analyzing zero gas. The final rule allows the low level gas concentration to be up to 20 percent of calibration span, which gives the tester the necessary flexibility to select an appropriate non zero, low level gas for such analyzers.

206. Comment: A low level cal gas has been added and this does not simplify or reduce testing costs. Along with new definition of span, the upper cal range has been significantly reduced, and 3 calibration levels of zero, mid, and span are adequate. Remove the low level requirement. ( 0041)

Response: We have not added a new low level gas in addition to the low, mid, and high levels required.

207. Comment: It is not clear whether it is acceptable to prepare cal gas mixtures from high concentration EPA Protocol gases in accordance to Method 205. If so, will this be acceptable to both EPA= s OAR and CAMD? ( 0059)

Response: Method 205 is allowed, except for Part 75 applications. Administrative approval is required to use the Method for Part 75 testing. 64 Section 7.2 Interference Check 208. Comment: The interference checks for most common O2 and CO2 analyzers are not necessary and the referenced requirements from Method 7E are entirely inappropriate for them. Oxygen and CO2 analyzers measure percent levels ( i. e., 10,000 to 210,000 ppm) so the interference check at levels of 10 to 50 ppm as specified in Method 7E is ludicrous. The choice of gases to inject for such tests is ( a) inconsistent with the existing Method 3A and Method 20, and ( b) inconsistent with even the most basic understanding of the analytical principals used for the diluent analyzers. Virtually all CO2 analyzers are infrared based systems and the interferences can easily be determined through basic spectroscopic considerations. Virtually all of the O2 analyzers that are used for such measurements are based on diffusion through zirconium oxide ( ZrO2), measurement of paramagnetic dipole moments, and electro catalytic ( fuel cell). The interferences for each of these analytical techniques are very well known and can be determined from standard chemistry and physics references, basic literature, and data provided by manufacturers. In almost every case, no interference test is needed nor can the cost be justified. Where such interference tests are needed and can be justified, they should be specific to the analytical method used. Interference checks should be the responsibility of the manufacturer for the given analytical technique ( 0032, 0036).

Response: We have revised the language in Section 8.3 to state that the O2 or CO2 analyzer must be documented to show that interference effects to not exceed 2.5 percent of the calibration span. The interference test in Section 8.2.7 of Method 7E is referenced as an example test for Method 3A where the analyzer is evaluated for the potential interferences encountered at applicable emission concentrations.

209. Comment: The cited Method 7E table reference should be 7E 3, not 7E 1. ( 0013, 0035)

Response: This correction has been made.

Section 8.1 Sampling Site and Sampling Points 210. Comment: This section refers to Section 8.1 of Method 7E for sampling points and stratification check, but the stratification check requires correction for diluent. Method 3A measures diluent. What is the stratification procedure if Method 3A is used without any other instrumental method? ( 0020)

Response: The sampling point and stratification check in Section 8.1 applies to Method 3A in general. We have clarified in Method 7E that a correction for diluent is not required for any of the stratification tests.

Section 8.2 ( untitled section)

211. Comment: There is no CO2 or O2 emission standard for any source. Therefore, the interference test for this method cannot be done as written. ( 0038) 65 Response: The proposed interference test was not tied to the applicable emission standard but was expressed as a percentage of the analyzer range.

Section 8.3 Sample Collection 212. Comment: If we need just CO2 and O2 for molecular weight or diluent correction, we use the exhaust of the M5 box directly to the analyzers. The proposed equipment requirements would not allow this and would require another person, or about $ 600 per day for this simplest of tests. Sections 6.1, 8.1, and 8.3 of Method 3A should allow the single point grab and single point integrated sampling procedures of Methods 3 and/ or 3B as well as the multipoint integrated sampling procedure. This allowance might be covered easier under the alternative procedures section. ( 0039, 0043)

Response: There is no prohibition against using Method 3 or 3B, if the applicable regulations allow these methods to be used. However, the final rule allows the use of the singlepoint integrated sampling described in Method 3 as an alternative to the Method 1 traverse points, when Method 3A is used only for stack gas molecular weight determinations.

Section 12.0 Calculations and Data Analysis 213. Comment: For clarity, state that the term for NO2 converter efficiency in proposed 7E, equations 7E 5 and 6, should not be used for other methods. ( 0039)

Response: For those methods that refer to Method 7E, the tester is directed to " follow the applicable procedures for calculations and data analysis in Section 12.0 of Method 7E." In Section 12.0 of Method 7E, the introductions to the converter efficiency calculations note that they are for NOx and have conditional use only for analyzers that convert NO2 to NO before measurement. It appears self evident that these converters are only used for NOx; we do not believe stating this in Methods 3A, 6C, 10, and 20 is necessary.

214. Comment: Add Aas applicable@ to the end of the sentence ( that references the procedures and calculations in Method 7E).

Response: This has been done.

Sections 13.1 and 13.2 215. Comment: The CO2 and O2 specifications should be revised to be absolute values rather than percentages. Two ( 2) percent of 25 is 0.5 percent CO2 or O2. Based on RATA data and experience, it is estimated that measurements can easily be made to within 0.2 percent CO2 or O2. For the bias test, 3 percent of 25 is 0.75 percent CO2 or O2, which is very loose and can introduce a large amount of error in combustion turbines with emission limits in lb/ mm Btu or at 15 percent O2. With all the RATA testing performed and reported for market based programs, the EPA has thousands of data points showing how well diluent monitors are operating ( 0032). 66 Response: We do not have sufficient data to warrant changing the current performance requirements.

216. Comment: Numerous commenters noted that the statement that bias be Aless than " 0.25 percent of upper range@ is extremely stringent and difficult, if not impossible, to meet. One commenter rightly noted that AYfor the zero gas@ should have followed the phrase, but was omitted. ( 0004, 0009, 0011, 0013, 0014, 0028, 0030, 0035, 0038, 0041, 0043, 0049)

Response: The sampling system bias specification of " 5% of span has been reinstated for all calibration gas levels.

217. Comment: Since there is no emission standard for O2 and CO, does this mean that I can pick any range I choose as long as I enclose the effluent concentration within the 20 percent of span and span gas bracket? Since 3A does not prescribe a range, you will find less scrupulous testers using the maximum range of 100 percent for some analyzers which is likely to have the opposite effect from what EPA is trying to accomplish. ( 0004, 0039)

Response: We believe that the revised definition of span addresses the commenter= s concerns. If a high range ( e. g., 25 percent O2) is selected, the final rule does not allow the tester to set the full scale range value equal to the span and use it for calibration error, bias and drift calculations, unless the actual emissions are between 20 and 80% of the full scale. If the O2 readings are low ( say 3 to 5 percent O2), then a lower span ( a fixed percentage of the full scale, e. g. 40 percent of the range, or 10 percent O2) would be required to meet the A20 to 80 percent@ guideline.

218. Comment: Does the final paragraph imply that pre and post test bias checks must be conducted using three gases? ( 0004)

Response: Section 13.2 does not imply that three gases are used for the bias checks. The bias test checks the system at the low concentration level and at the mid or high level concentration, depending on which level is closer to the measured concentration. The test only uses two gases. The low level gas may be a zero gas, at the discretion of the tester.

Section 16.1 Dynamic Spiking Procedure and Manufacturer's Stability Test 219. Comment: Since O2 and CO2 are typically not subject to any significant bias or matrix effects, the spiking procedures are superfluous and should be removed. I know from experience with other methods that some regulators will end up requiring an alternative in addition to the normal criteria just because it is there. ( 0039)

Response: We agree and have dropped the proposed alternative dynamic spiking procedure from Method 3A.

3.15 Specific Comments on Method 6C General comment 67 220. Comment: Based on the August 1997 proposal, the commenter disagrees with setting an 80 percent limit on concentration of interest. By not defining the analyzer span with respect to the level of measurements to be made ( as was previously done), EPA is encouraging the use of non optimum analyzer ranges ( spans). Measurements up to 100 percent of the concentration of interest should be allowed. By restricting the measurements to 80 percent, EPA is forcing the use of artificially high calibration gases. Furthermore, many sources are tested at emission levels significantly below the emission standard ( concentration of interest) and the proposed change will force the use of high level calibration gases that are inappropriately high. ( 0038)

Response: We believe that the revised definition of span and the accompanying guidelines in the final rule address the commenter= s concerns. The revised span definition and guidelines encourage the use of appropriate calibration gases, with concentrations in the vicinity of the actual emission levels.

221. Comment: In the first proposal in August 27, 1997, the calibration error specification was changed from " 2 percent of the span for the zero, mid range and high range calibration gases" to " 4 percent of the concentration corresponding to the emission standard for any of the calibration gases." This specification may be tighter or looser depending on the measurements being made. ( 0038)

Response: The calibration error specification given in the August 1997 proposal has been dropped. The 2 percent of calibration span specification for analyzer calibration error has been retained.

222. Comment: In the August 1997 proposal, the sampling system bias test specification has been changed from " 5 percent of the span for either the zero or upscale calibration gases" to " 10 percent of the concentration corresponding to the emission standard." Disregarding the fact that the equation does not work, the change could be a tighter or looser specification, depending on the relationship of the measurements being made to the high level calibration gas. ( 0038)

Response: The bias specification given in the August 1997 proposal has been dropped. The 5 percent of calibration span specification for sampling system bias has been retained.

223. Comment: There are no instructions for how to determine " the concentration corresponding to the emission standard." For each electric utility steam generator, this SO2 or NOx concentration ( in ppm) will vary depending on the diluent ( CO2 or O2) concentration. It will also change with time as the boiler responds to process changes. ( 0038)

Response: We have dropped the proposed determination of performance tests based on the applicable emission standard Section 1.0 Scope and Application 68 224. Comment: The proposed method is completely devoid of any relevant discussion of sensitivity, minimum detection limit, and practical quantification limit and should be revised to address these issues explicitly. These issues commonly arise in determining the applicability of the method and interpretation of the results. These issues should be addressed by the method developers or at the time a method is proposed and promulgated rather than being left open for interpretation by others years later ( 0032).

Response: We believe that requiring calibration gases in the proper range such that measured emissions will be within 20 to 80 percent of the span is appropriate in lieu of specifying minimum detection limits and practical quantification limits. Instrument sensitivity normally varies according to principle of operation. We note in the methods that sensitivity is generally less than 2 percent of the calibration span.

Section 1.3 Data Quality Objectives 225. Comment: Section 1.3 refers to Method 7E, Section 1.3, which refers to Section 13, which refers to Section 1.3; this is confusing. ( 0035)

Response: The commenter is correct. However, we have dropped the proposed data quality assessment procedures and requirements.

Section 3.2 Interference Check 226. Comment: The interference check is spelled out in Method 6, but abbreviated in Method 7E. There is a great deal of confusion, over specification and under specification that occurs with this " cost savings" way of writing the methods. In the long run, it would be cheaper to have each method stand alone with each section having been carefully thought out for that method/ instrument. ( 0035)

Response: We understand the commenter's concern. We are not able to publish the methods as stand alone methods because of our convention in method writing. However, by making the methods consistent as we are in these revisions, being knowledgeable of Method 7E makes one knowledgeable of the requirements of the other methods as well.

Section 4.0 Interferences ( Reserved)

227. Comment: This section is reserved yet extensive resources are required to conduct interference checks of SO2 analyzers. Potential documented interferences should be discussed in this section and methods for eliminating or minimizing the effects should be included. The discussions should include sampling system interferences such as the presence of ammonia which can lead to the formation of ammonium bisulfate or other salts or absorption of SO2 within the condenser system. In addition, cogent explanations of expected analytical interferences for infrared, fluorescence, and differential adsorption analytical techniques should be included. ( 0032) 69 Response: We have added a note to Section 4.0 directing the reader to refer to Section 4.1 of Method 6 for a discussion of interferences. Describing other potential interferences not covered in Method 6 is beyond the scope of this rulemaking.

Section 6.0 Equipment and Supplies 228. Comment: The referenced equipment specifications for Method 6C in Method 7E will not prevent reactions of SO2 and ammonia within the sampling systems. Where ammonia concentrations are significant relative to SO2 concentrations, use of condensers to remove effluent moisture will result in low biased SO2 results. Furthermore, the sampling system temperatures in Method 7E are not sufficient to prevent certain gas reactions and adsorption on surfaces ( 0032).

Response: The interference effects of ammonia on SO2 are discussed in Section 4.1 of Method 6, which is now cited in Method 6C.

229. Comment: Figure 7E 1 is incomplete in regards to heated sampling lines. ( 0035)

Response: We have revised the figure to note the areas where the sampled gas should be above its dew point.

Section 6.1 What do I need for the measurement system?

230. Comment: For wet based systems ( i. e., dilution or hot wet extractive), moisture removal systems and heated sample lines are neither performed nor essential. In stack dilution probes may not need a heated sample line depending on the dew point of the sample. Dry based extractive systems may use a combined sample probe/ moisture removal system after which an unheated sample line may be used depending on the dew point. ( 0009, 0010, 0059)

Response: We agree with the commenter that dilution systems should be addressed. Performance based provisions are added to the final rule for using dilution systems.

231. Comment: It seems like a modified Method 5 box with hot probe, filter, and moisture removal system hung from a rail could work for a traversing gas sampling system which would not be allowable with your proposed heated line requirement. The heated line should not be a requirement. ( 0043)

Response: The noted modified Method 5 setup is allowed under the provisions of the current methods. For clarification, we have replaced the specifications for essential components with performance based criteria. This eliminates the restriction in the proposal noted by the commenter.

Section 6.2 SO2 Analyzer 232. Comment: The use of specific technologies should be removed from this section and moved to the preamble, if mentioned at all. The goal should be performance based systems, and referring to specific instruments and components undermines that goal. ( 0009, 0054) 70 Response: We agree that our goal is performance based systems. However, we don= t believe that mentioning technologies that have been successfully used previously necessarily undermines this goal.

Section 6.3 What additional equipment do I need for the interference check?

233. Comment: Section 6.3 states that in cases where the emissions concentrations are less than 15 ppm, the alternative interference check in Section 16.1 Ashould be used@, but Section 8.3 states Amust be <EMAIL_ADDRESS>Please clarify. ( 0025, 0030, 0038)

Response: The current language has been clarified to note that the alternative interference check must be used when routine measurements below 15 ppm are made .

234. Comment: This section references an interference check sampling train in Figure 6C 2. Are interference gases introduced directly into the analyzer or via the sampling train for the interference check sampling train in Figure 6C 2? ( 0025)

Response: The proposed reference to Figure 6C 2 in Section 6.3 was in error. The reference should have been to Figure 6C 1 which is now the alternative interference check sampling train. In this alternative procedure, real time emission samples are collected through the sampling train to determine interferences; interference gases in cylinders are not used. For the normal interference check using cylinder gases, the interference gases are introduced into the measurement system for the interference check.

235. Comment: Figure 6C 1 illustrates an interference check sampling train. There is no Figure 6C 2, and reference should be to 6C 1. Figure 6C 1 does not illustrate heated sample lines. Is there a procedure for the modified Method 6 other than the figure? ( 0035, 0043)

Response: See the response to Comment 234. The modified Method 6 sampling train interference equipment shown in Figure 6C 1 collects a sample from the sample by pass vent which is after the Method 6C moisture removal system as shown in Figure 7E 1. Therefore, a heated sample line is not necessary. Also, there is a discussion of the Modified Method 6 procedure in Section 16.1.

236. Comment: The alternative interference check is detailed in Section 8.3 as opposed to 16.3. ( 0043)

Response: We moved our alternative interference check discussion to Section 16.1.

Section 7.2 Additional Cal Gas Requirements for Fluorescence Analyzer 237. Comment: Section 7.2 contains a requirement that is virtually impossible to meet as written for fluorescence based analyzers because it requires that the O2 and CO2 concentration in the calibration gas be within 1 percent absolute O2 and CO2 of the concentration in the sample. This section needs to be re worded so that it applies this requirement to the sample gas and 71 calibration gas as delivered to the analyzer so that dilution based systems can be used to meet this requirement as has been done for many years. Dilution of the sample stream by 20 to 1 usually satisfies this specification. Nomographs provided by the gas vendor are not adequate to correct for quenching affects, and their use should not be allowed. We believe this requirement stems from a quenching problem that was fixed more than 20 years ago, and EPA should research this and obtain up to date information. Note that hundreds of fluorescence analyzers are in operation under the Acid Rain Program, and there have been no reports of quenching problems. ( 0009, 0032, 0033, 0038, 0059)

Response: These concerns for dilution systems have been addressed in the final rule. We have dropped the requirement that calibration gases be within 1 percent O2 or CO2 of the corresponding concentration in the sample and have dropped the reference to nomographs.

238. Comment: In Section 7.2, there is an attempt to deal with third body quenching associated with fluorescence analyzers. Once again, the method assumes that full strength extractive technology will be used, either wet or dry. Dilution based sampling systems and extractive systems with diluters just prior to the SO2 analyzer limit the effects of third body quenching by diluting the sample stream with SO2 free air. For a 50: 1 diluted sample, the O2 concentration will be between 20.5 ( no O2 in pre diluted sample) and 20.9 percent ( 20.9 percent O2 in the pre diluted sample). Varying the amount of O2 or CO2 in the calibration gas will cause little change in the O2 concentration at the analyzer. Therefore, it is recommended that this section be rewritten to recognize that where a steady state of O2 is present at the analyzer, as is the case in dilution sampling systems, these restrictions do not apply.

Response: See the response to Comment 237.

239. Comment: Is it really the gas vendor that knows the quenching effect of O2 or CO2 on our analyzers? It seems more likely that it would be the analyzer manufacturer. Do gas vendors account for quenching on their analyzers when they certify the gases? Recommend changing Agas vendor@ to Agas analyzer <EMAIL_ADDRESS>How significant is the quenching factor in any analyzer especially in the ambient level analyzers used with dilution extractive systems? Could nomographs be used with dilution extractive systems? ( 0043, 0054, 0059)

Response: The quenching effects of O2 and CO2 on an analyzer should be addressed by the gas analyzer vendor. Any quenching effects would not likely occur at currently used dilution rates. See the response to Comment 237.

240. Comment: What is the reason for O2 and CO2 concentrations to be within 1 percent of actual stack gas? ( 0028)

Response: This 1 percent O2 and CO2 tolerance in Method 6C applies only to fluorescence analyzers and accounts for the gas quenching effects for this type analyzer. This is an obsolete caution and we have not included it in the final method.

Section 7.3 Interference Check 72 241. Comment: All of the requirements to conduct interference tests for analyzers based on infrared adsorption, UV differential adsorption, and fluorescence should be deleted based on thousands of previous tests that have been conducted that demonstrate the absence of interfering affects already conducted for properly designed systems. The necessary data to justify this decision is reported to the EPA each year. EPA should tabulate and publish a list of conditions under which historical interference tests have been reported to have been failed. ( 0032)

Response: These instrumental methods are performance based. Conducting the interference test confirms that the measurement system is properly designed. We are allowing the analyzer manufacturers to perform the initial interference test. We will gladly make available summary data listing conditions under which historical interference tests have failed if such data is provided to us.

242. Comment: Interference tests for analytical techniques not previously demonstrated should be designed to be specific to that analytical technique and based on information provided by the analyzer manufacturer. The interference gases specified in Method 7E are clearly not appropriate for SO2 analyzers. The alternate interference check based on a side by side comparison of the instrumental test method with the modified impinger method was a crude approach 20 years ago and is no better now. It involves comparing a more accurate and precise instrumental method with an inferior manual method. This presents the same problems as trying to compare 3 runs of Method 5 with optical particulate matter process monitors. ( 0032)

Response: Since we are allowing the analyzer manufacturers to perform the interference test on analyzers, this would cover techniques not previously demonstrated. The side by side interference test using a modified Method 6 train is now listed as the alternative interference procedure. The primary interference check follows the procedure listed in Method 7E where the measurement system is evaluated against potential gas interferents. Only those interferents listed in Table 7E 3 that are applicable need be evaluated.

243. Comment: We disagree with requiring annual interference checks.. Additionally, no provisions have been made for cases when low SO2 emissions are encountered, as was provided in EMTIC TID 12, dated April 14, 1992. These tests are neither simple nor cheap and should only have to be done once per source category per instrument type. ( 0034)

Response: The proposed requirement to conduct annual interference checks has been dropped. A manufacturer stability test is required for instruments that routinely measure low concentrations. For the interference check, the manufacturer may certify the measurement system using the appropriate interference gases for the intended applications.

244. Comment: The concentration options for the Method 6C interference check are very unclear. Section 7.3 of Method 6C calls for a comparison with Method 6 for concentrations greater than 15 ppm and refers to using the test gases in Table 7E 3 of Method 7E for concentrations less than 15 ppm. Section 7.3.1 of Method 6C adds confusion by apparently allowing the test gases in Table 7E 3 for the interference test at the discretion of the tester. ( 0035) 73 Response: In the proposal, the intent was to allow either interference check ( comparison against modified Method 6 or using the test gas procedure in Method 7E) during tests at concentrations above 15 ppm. Tests routinely performed below this concentration must only use measurement systems that were evaluated by the procedure in Method 7E. This is the case in the final Method 6C, except that the primary interference check is the procedure in Method 7E and the comparison against modified Method 6 is the allowed alternative.

245. Comment: This section as well as Sections 8.3 and 13.2 cover the interference check. Too many interference checks are allowed for this method. Sections 7.3, 8.3, and 13.2 detail an obsolete ( Method 6 comparison) interference check and should be deleted in favor of retaining Section 7.3.1 which describes the new interference test method. This would meet the state intention to Aremove obsolete specifications, harmonize similar requirements, and simplify to enhance the method= s utility and reduce the cost of testing.@ A Section 16.3 should be added to Method 7E to incorporate an Annual Primary Interference Gas Recheck. ( 0041)

Response: We have attempted to add what we think is a superior interference check without completely eliminating the procedure that was acceptable in the past. By continuing to allow the traditional interference test against Method 6 as an option, we will not be placing an immediate burden on testers to recertify their equipment by the new interference check. We believe testers will eventually phase out the old interference check.

Section 7.3.1 Alternative Analyzer Interference Check 246. Comment: This section should clarify that for dilution systems, gases should be injected at the probe, not directly into the analyzer. This is so the analyzer is operating in the same manner as when it will be used in the field. ( 0009)

Response: The commenter is correct. Dilution sampling systems should be evaluated by introducing the interference gases in system calibration mode. This has been noted. The final rule also specifies that a system calibration error test must be done for a dilution type system, in lieu of analyzer calibration error and bias checks. This accounts for the fact that the analyzer calibration error test ( which requires direct injection) is not feasible for dilution systems.

247. Comment: This section is flawed. It is possible to introduce gases listed in Fig. 7E 3 one at a time without SO2, since SO2 is likely to react with some of the listed gases ( i. e., ammonia, water). ( 0011)

Response: The commenter makes a good point. We now note that the appropriate interference test gases that are potentially encountered during a test are used for the interference test.

248. Comment: The original interference check does not state at which level. The repeat is at 80 percent of the range, which is also unclear as to what range. ( 0035)

Response: We have added clarity to the description of the interference check. The level of test gas used in the interference test is shown in Table 7E 3. When the test gas is evaluated 74 with the pollutant gas present, the pollutant concentration should be 80 to 100 ppm. If the test is to certify the analyzer for low measurements, the pollutant concentration should be less than 20 ppm. For multi range instruments, the most sensitive scale that will be used for field testing must be used for the interference check.

249. Comment: Where is Figure 6C 8? ( 0035)

Response: The citation was in error and now reads AFigure 7E 4.@

250. Comment: The interference check procedure should be in Section 8. Section 7 is for reagents/ standards. ( 0035)

Response: We agree that the alternative interference check discussion is out of place in Section 7. It has been moved to Section 16.

251. Comment: No one can pass this check because it is incorrect. I think it should say introduce SO2 with and without the gases listed in Figure 7E 3, one at a time. ( 0035)

Response: We agree, and the wording is revised to reflect this.

252. Comment: The alternative interference checks are expensive to perform and will cost more than $ 11,000 per year to implement. This test will make it hard for small companies to compete. ( 0043)

Response: We have dropped the yearly interference check requirement in favor of requiring additional rechecks only when a major analyzer component is changed. If you have many analyzers of the same make and model, you need test only one of them. Also, if the instrument manufacturer performs the test on your analyzer or on one of the same make and model, and provides documented test results, this is acceptable.

253 Comment: The procedure needs a more detailed explanation. Specifically, explain what is meant by with and without SO2. ( 0049)

Response: The procedure has been revised to add detail and clarity.

Section 8.1 Sampling Site and Sampling Points 254. Comment: Method 6C requires meeting a 5 percent criterion for single point testing and a 10 percent criterion for 3 point traversing. How can this be done on a variable source? ( 0035)

Response: You may not be able to take advantage of the fewer points option at sources that vary. 75 255. Comment: For the stratification test, this section requires the SO2 diluent corrected concentration to be less than 5 or 10 percent to use less than 24 points. This will hardly ever happen on an SO2 source. Therefore, the cost of a test will increase by 2 4 times. Does this new method apply to a RATA? ( 0035)

Response: The stratification requirements in Method 7E do not apply to RATAs. Section 8.1.1 of Method 7E states that performance specification testing of CEMS should follow the sampling site procedures in the appropriate performance specification or applicable regulation. If the applicable regulation or performance specification requires stratification testing for a RATA application, then you must meet that requirement.

Section 8.2 Measurement System Performance Tests 256. Comment: This section refers to Method 7E, Section 8.2.5, among others. Section 8.2.5 refers to Table 7E 2, but there are two tables named 7E 2. I am assuming you mean the second one. ( 0035)

Response: The commenter is apparently confusing Figure 7E 2 and Table 7E 2.

Section 8.2.5 Initial Sampling System Bias Check 257. Comment: This section refers to other sections for the bias calculations and acceptance criteria. Everything should be together in the bias check section. ( 0035)

Response: For consistency, all of the acceptance criteria are found in Section 13 B Method Performance. We believe the bias calculation should remain in the calculations section B Section 12.

258. Comment: This section incorrectly refers to Section 12.5 for bias check calculations. Section 12.5 is the NOx converter efficiency equation, while 12.4 refers to bias checks. ( 0035)

Response: This correction has been made.

Section 8.3 Interference Check 259. Comment: There is text explaining how to perform the interference check. Do these instructions also belong in Method 7E, or is this specific to Method 6C? ( 0025)

Response: The instructions primarily describe the Method 6C interference test where Method 6C is compared to Method 6. These are specific to Method 6C only.

260. Comment: How long is a run by modified Method 6, or what total volume? ( 0035) 76 Response: The modified Method 6 sampling time per run shall be the same as for Method 6 plus twice the system response time. This inadvertent deletion in the proposal has been added to Method 6C.

261. Comment: There is no Figure 6C 2; the reference should be 6C 1. The figure makes no sense. There is no explanation of what it is or how it is supposed to be used. ( 0035, 0038)

Response: The reference to Figure 6C 2 has been corrected to Figure 6C 1. We have noted in the title that the figure depicts a modified Method 6 interference check sampling train.

262. Comment: Please define source category and type of facility. ( 0043)

Response: The terms " source category" and " type of facility" have been dropped from the methods. A facility is now characterized by its potential to have interferences.

263. Comment: Has EPA found that SO2 analyzers are so bad at discriminating just SO2 that all of the interference check procedures are necessary? Has EPA determined that Method 6 is immune to these interferents as well? For all this effort, it may make more sense to abandon the analyzer and use the old Method 6. ( 0043) The interference check creates additional and unnecessary work. As an example, a Kraft mill might have 7 to 10 source categories on site. Why not just use Method 6? Interferences are specific to the principle of operation, not analyzer specific, and one test per lifetime of the analyzer should be adequate, as it is now. ( 0039)

Response: We have reduced the frequency of the interference check to initially and after any major analyzer component is replaced.

264. Comment: Method 6C does not require the analysis of performance audit samples when conducting the interference check. Why not require this analysis? It would appear that this analysis would resolve any discrepancy in results. ( 0059)

Response: We have added the requirement that performance audits be analyzed with modified Method 6 in the interference check.

265. Comment: The EPA should clarify that the pollutant of interest should be in the test gas ( such as wording to use gases with and without NOx). Also, the EPA and/ or manufacturers should be able to establish interference effects on analyzers without the burden being on the testing community. ( 0039)

Response: We agree that the test gas wording was vague and have improved it. We allow initial interference certification by the manufacturer and have dropped the requirement to repeat the test yearly unless a major analyzer component is replaced.

266. Comment: The interference check as described is flawed and unreasonable. Gas analyzer manufacturers have done extensive research, development, and testing prior to manufacturing any analyzer. The gas analyzer manufacturers incorporate components such as 77 optical filters and reduced pressure reaction chambers to create an analyzer that performs to a specific need with minimal interference. The available NOx analyzers have already been rigorously evaluated under controlled conditions for their performance. It is unnecessary to repeat gas interference checks on analyzers that have been carefully researched, developed, and tested by the gas manufacturers. It is true that there are specific gases that can interfere with the NOx gas analyses. Carbon dioxide ( CO2), oxygen ( O2), water vapor ( H2O) and ammonia ( NH3) are the most likely gases to be encountered during flue gas testing that may interfere with the measurement of NOx.

Ammonia creates a unique problem. The main concern with ammonia is that stainless steel NO2 converters will change NH3 to NO which will be detected in the reaction chamber of a chemiluminescence NOx analyzer. Molybdenum and carbon converters do not have this problem. Additionally, free NH3 has a tendency to combine with other compounds such as NO2, SO2 and HCl. A common problem with chemiluminescence analyzers is that free NH3 combines with NO2 in the reaction chamber to form crystals that will eventually blind the detector. Any NO2 existing in the sample stream may combine with NH3 before the moisture removal system, in the moisture removal system and/ or prior to the analyzer. If a source is known to have free NH3 in the gas stream then every effort should be made to prevent ammonia salts from forming and place a NH3 scrubber in the sample gas that is directed to the NOx analyzer. Ammonia scrubbers are available from commercial vendors.

If an NDIR analyzer is used to measure NOx, then the primary interferences are CO2 and H2O. As with any NDIR analyzer, CO2 and H2O will send a false detection since CO2 and H2O have many absorption intensity peaks in the infra red spectrum. Optical filters can improve the discrimination ratio for both CO and H2O. Additionally, by having an efficient moisture removal system will minimize H2O interference. There should be established interference CO2 and H2O rejection ratio for NDIR NOx analyzers. Analyzer manufacturers should be required to present data to confirm their claimed interference rejection ratios. It is absurd to require an interference test on a yearly basis. Does the principal/ theory change every year? ( 0011)

Response: We have reduced the frequency of the interference check to initially and after any major analyzer component is replaced. The instrument manufacturer may also conduct the initial interference check.

Section 8.4 Sample Collection 267. Comment: What happens to the test data when the sample flow rate has exceeded the 5 percent criterion during a run? ( 0035)

Response: In the final rule, this rigid flow rate requirement has been dropped. It has been relaxed to a guideline ( suggestion) to keep the flow rate within 5 to 10 percent of the target rate.

268. Comment: Rather than specifying that flow be within 5 percent of that during the bias check, how about giving the option of proving the ( in) sensitivity to flow rate? The same would apply to other instrumental methods. Additionally, how often do we need to record the flow rate? I assume some sort of documentation is needed. ( 0043) 78 Response: See the response to Comment 267.

Section 12.4 [ Should be 12.0 that references 12.4 in Method 7E]

269. Comment: It says a bias test is the system response. Calibration gas value divided by cal gas value. If that is the case, why do we need a calibration error test as a correction? Should the equation be: Cs Cdir/ ( either Cdir or Cv)? ( 0035)

Response: The analyzer calibration error test ( direct injection) is needed to establish the accuracy of the analyzer and the linearity of its response across its measurement range. The bias check indicates the inaccuracy ( over and above the analyzer calibration error) that is introduced by pulling gas through the entire measurement system. The pre and post run bias check data are used to Adial out@ this inaccuracy in the concentration measurements. The equation referenced by the commenter was found to be incorrect. It has been corrected in the final rule.

Section 13.2 Interference Test 270. Comment: The need for an interference test of this type seems excessive. Interference is inherent to the design of the monitor and does not change over time, and does not need tested on a recurring basis. Why was 12 months chosen as the limit for proof of interference? Has data shown that response to interferents changes over time? ( 0009 ,0043)

Response: We have reduced the frequency of the interference check to initially and after any major analyzer component is replaced. The instrument manufacturer may also conduct the initial interference check.

271. Comment: Has anyone actually done this interference test at a source? Where does the 7 percent come from? What is the modified Method 6? In what units are the results presented? ( 0035)

Response: The modified Method 6 interference test is not a new requirement but has been the required interference test for Method 6C in the past. We are not changing this procedure in the rulemaking.

Section 13.3 Alternative Interference Check 272. Comment: This section refers to Section 13.6 of Method 7E which only gives the criteria for acceptance for normal testing of 2.5 percent. It should reference Section 7.3.1 of Method 6C. ( 0035)

Response: In the final rule, the acceptance criterion for the interference check described in Section 8.3 of Method 6C is presented in Section 13.2. For the alternative interference check, Section 13.3 of Method 6C cross references the specification in Section 13.7 of Method 7E.

Section 13.1 79 273. Comment: If the standard is 2.0 ppmv, then a bias of 0.5 ppmv is acceptable? ( 0035)

Response: Yes.

3.16 Specific Comments on Method 7E General comments:

274. Comment: We suggest that EPA produce an accompanying guidance document, such as the ones used for Part 75 monitoring or compliance assurance monitoring, for frequently asked questions and easier to update pieces than a full rule. We suggest the equipment in Section 6.1 be in the guidance document, and a new Section 6.1 that would be very general and technology neutral. The table matrix in 7E 3 will become obsolete quickly and a guidance document would be useful. (( 0022, 0023)

Response: A guidance document may be a good idea, and we will consider it for a future project as time and resources allow.

275. Comment: For sources that emit ammonia at detectable levels (> 1 ppm), we suggest EPA require testers to add permeation tube ammonia scrubbers to their NOx sampling and conditioning system. ( 0038)

Response: In this rule, we are refraining from requiring specific interference limiting technology but are allowing testers and manufacturers flexibility in their approach to handling interference problems.

276. Comment: The Method 7E procedures do not specify using the larger of the absolute values for each interferent ( between introducing the interferent with and without the contaminant) be used to calculate the interference, as the other methods do. ( 0020)

Response: We now state that, in summing the interferences, use the larger of the absolute values obtained for the interferent tested with and without the pollutant present.

Section 1.1 Analytes 277. Comment: The parenthetical phrase is in the wrong location. It should be after the methods listing in Section 1.0. The question posed in Section 1.1 seems to be addressed by the table, but the table= s placement makes it confusing. ( 0032)

Response: The parenthetical phrase has been moved to the end of Section 1.0, a more appropriate place.

278. Comment: Add a clarifying statement that the method is for NOx as NO2. ( 0007) 80 Response: This statement has been added.

Section 1.3 Data Quality Objectives ( DQO)

279. Comment: The statement, " In applications where there is no emission limit ( e. g., market based programs)" is false and should be revised. Virtually all sources that are included in market based programs are also subject to emission standards through other applicable regulations. Furthermore, it is impossible for the tester to distinguish between the purpose of specific tests programs at such sources because the test results may serve to demonstrate conformance with multiple requirements ( 0032).

Response: This comment has been addressed by our not basing the performance tests on the applicable emission standard.

280. Comment: The section states that the method is designed for determining compliance with Federal and State emission standards. The proposed revisions represent some major deviations from many of the commonly used aspects, and could result in data that is less comparable to other methods that now refer to Method 7E as the standard, such as CEM certification tests, CEM QA audits, emission inventory tests, and control device performance evaluations. ( 0012)

Response: A major intent of the method revisions is to improve the quality measured data. We believe the revisions we have made to the methods will enhance their standing as standards rather than diminish it.

281. Comment: The following sentence is poorly written: AHowever, we do not intend the method to penalize you for calibrating to measure accurately emissions well below the emission limit.@ ( 0043)

Response: We have rewritten this section.

Section 1.3.1 Data Quality Assessment 282. Comment: I do not understand how conducting a bias test prior to ( optional) and post test ( mandatory) qualifies as a Data Quality Assessment, and this section does not tell the reader how to assess data quality mostly because no objectives were set. Most performancebased systems involve dynamic spiking certainly with CEMs. ( 0035)

Response: We have dropped the proposed requirement to calculate data uncertainty using the results of the bias test. As a result, the proposed discussion of data quality assessment using the bias test results in Section 1.3.1 has not been retained.

283. Comment: Two problems exist with the statement Aif the measured average emissions are less than the emission limit but a small fraction of the data exceeded the analyzer range, the data user may elect to accept this data as adequate to show compliance with the emission limit.@ First, data that exceed the analytical range are unknown values and cannot be 81 included in the averages, and second, subjective statements like Acould@ or Amay@ are ambiguous and confusing. ( 0011)

Response: We have dropped the proposed requirement to calculate and report the uncertainty of each test run.

Section 1.3.2 Data Quality Assessment for low emitters 284. Comment: The reference should be to Section 13.5 for the low level bias and Section 13.8 for the alternative dynamic spike. ( 0013, 0035)

Response: These comments on the proposal do not apply to the revised section that now addresses low emitters.

285. Comment: Why is this criteria only interim? The NOx analyzer is the only instrument in the grouped methods that can meet the bias criteria for lower levels. The other methods won= t be able to do it in 3 yrs or 10 yrs. New instruments are needed, not interim relief. ( 0035)

Response: We have dropped the statement giving interim relief for 3 years.

286. Comment: Modify the first sentence to AYes there are interim special sampling system bias performance criteria and allowances when using the alternative.@ ( 0054)

Response: The text of this section has been revised for greater clarity.

Section 1.3.3 How is the calibration designed when test units are covered by more than one emission limit?

287. Comment: This section states that the analysis should be based on the most stringent emission limit. For a source with an average low level limit for normal operation and a short term high level average ( i. e. dual range analyzer), which one is the most stringent? ( 0022)

Response: For a source that has an average low level limit for normal operation and a short term high level limit, the analytical calibration must be designed to cover both limits. For example, a dual range analyzer could be used.

Section 3.0 Definitions 288. Comment: This section has no definition of the term uncertainty estimate. This term is used ( and misused where bias is explicitly and implicitly stated to be uncertainty) frequently in this method and should be defined because the meaning is not apparent from the context. In addition, the definition for apparent bias is missing. ( 005, 0013, 0032)

Response: See the response to Comment 283. 82 289. Comment: We recommend you add the following definitions ( 0054):

a. Emission limit: Analyte concentration as written in the unit= s Permit to Operate.

b. Applicable Emissions Standard Correction: Analyte concentration corrected to one of the standards listed in Table 12.1.1.

c. Run: Consecutive series of gas samples taken at a single point, 3 point, or a single traverse across the stack or duct in minutes. Number of required minutes listed in 13.3.

d. Test: Sum total of all runs in minutes.

Response: Definitions for " run" and " test" have been added to Method 7E. " Emission limit" and " applicable emissions standard correction" are not now needed in the final methods.

Section 3.1 Analyzer calibration error 290. Comment: The sentence should end with Adivided by the certified calibration gas concentration:. ( 0013)

Response: The commenter is correct for the proposed rule; however, we have revised the analyzer calibration error to be the difference between the two measurements divided by the calibration span.

Section 3.2.2 System calibration 291. Comment: The definition should state that the gas be introduced prior to the sampling filter. ( 0035)

Response: The system calibration means introducing the calibration gases into the measurement system at the probe and upstream of all sample conditioning components. The filter is considered a sample conditioning component. Even so, we have mentioned the filter in the definition as recommended.

292. Comment: Clarify if it is acceptable to both the EPA Office of Air Quality Planning and Standards ( OAQPS) and the Compliance Assurance Monitoring Division ( CAMD) to use Method 205 to obtain the required concentrations, provided the high concentration gases conform to EPA Protocol. ( 0059)

Response: Method 205 is acceptable to OAQPS, but Administrative approval from CAMD is required to use it in Part 75 applications. This has been explicitly stated in the method.

Section 3.5 Data recorder 83 293. Comment: In the definition for data recorder, the term Apermanent@ is interesting and could mean a line on paper or an electronic logger. This implies that data read to a spreadsheet is only permanent if it is write protected. Please clarify. ( 0043)

Response: " Permanent" in this instance means documented.

Section 3.9 Range 294. Comment: This definition allows the range to be greater than 5 percent of the spanlevel concentration. Although there is no upper limit, it is somewhat restricted by the reduction in sensitivity. There is an incentive to use a high range limit since the calibration error for zero gas is set at 0.25 percent of the upper range limit ( 0032).

Response: The methods now require that no run average exceed the calibration span concentration.

295. Comment: The definitions for range and span ( here and in Section 3.12 and the definition for span level gas in Section 7.1.1 seem to add unnecessary complication for determining analyzer measurement range, span value, and calibration gas levels. An approach similar to the straightforward fashion of Method 25A could be adopted if the objective is to improve the QA/ QC aspects of the new methods. ( 0029)

Response: We have dropped the definitions of Arange@ and Aspan@ since span as a single term is not used in the newly adopted terminology and range is used only sparingly. To simplify the terminology, we have changed Aspan level gas@ to Ahigh level gas.@ The Arange@ generally refers to the interval between the minimum and manufacturer recommended maximum concentration for the analyzer full scale response. The Acalibration span@ is defined as a fixed percentage of the analyzer= s full scale range and is chosen such that the majority of the measured concentrations will be between 20 and 80 percent of this calibration span.

296. Comment: Most instruments have several ranges, so it would be more appropriate to define range in terms of the measurement scale selected on the analyzer, and say that range is the interval between the nominal minimum and maximum concentration on the selected analyzer measurement scale. The inclusion of language cited by the manufacturer could have the very undesirable effect of opening the door to an analyzer certification program similar to that used for ambient instruments. ( 0059)

Response:. See the response to Comment 295.

297. Comment: It seems appropriate to replace the proposed span definition with one for span value, which would be the highest concentration of the calibration curve and a value no more than 20 percent above the highest calibration gas. ( 0029)

Response: We do not use Aspan value@ because it is a different term that normally applies to the calibration of CEMS and is determined in the applicable regulations. 84 298. Comment: You should only recommend that the range be at least 5 percent greater than the concentration of span gas, not make it a requirement. If the bias result is off scale, the test should not be valid, however. It is unlikely that a bias result would be higher than the span gas. This issue is not that important unless the value is off scale, but some regulators like to pick on it. ( 0043)

Response: This proposed requirement has been dropped in the final rule.

Section 3.10 Response time 299. Comment: Why don= t you say it must be greater than 92.5 percent for three readings, not varying by more than 0.5 percent of the cylinder value? ( 0035)

Response: We have revised some of the response time criteria to make it less conflicting. Now the response time is measured when the upscale gas has reached 95 percent of its certified value or 0.5 ppm ( whichever is less restrictive) or when the low level gas has decreased to within 5.0 percent or 0.5 ppm ( whichever is less restrictive) of its certified value.

Section 3.11 Sampling system bias 300. Comment: It is more accurate to refer to the analyzer, as opposed to the analytical system. ( 0029)

Response: The revised system bias definition clarifies this.

301. Comment: There is a conflict between the sampling system bias definition and the calculation in Equation 7E 3. ( 0035)

Response: This has been corrected in the revised definition and calculation.

Section 3.12 Span 302. Comment: The definition of span has changed, and is now based on the calibration gas instead of the analyzer range. Use of a higher level calibration gas will change the span value, and this does not make sense. ( 0008)

Response: See the response to Comment 295.

303. Comment: Ambiguity exists between the definition of span as the concentration of the highest calibration gas in this section, maximum concentration considered potentially valid for a test in Section 7.1.1, and chosen such that all measurements are all below the span in the QA/ QC Summary Table. ( 0041)

Response: We now use " calibration span" in place of " span." See the response to Comment 295. The noted points of ambiguity do not conflict. The calibration span is the 85 concentration of the highest calibration gas; this concentration set the upper calibration limit for valid, quality assured data, which means that it should be chosen such that no run averages exceed this concentration.

304. Comment: I= m not sure that the span in most cases will be higher than the concentration of the emission limiting standard. The relationship of the span to the emission limiting standard is often based on age of the standard in relation to the source. Span should always be selected such that the expected concentration is 25 to 30 percent of the span to ensure meaningful results. ( 0059)

Response: See the response to Comment 295.

Section 4.0 Interferences ( Reserved)

305. Comment: This section is reserved, and this is entirely incongruous and inconsistent with the fact that onerous interference testing procedures are required initially and annually for each analyzer and for each source category ( 0032).

Response: A brief discussion has been added to Section 4.0 to note that interferences may vary among instruments and that instrument specific interferences must be evaluated through the interference test. The proposed requirement to conduct the interference test annually has been dropped.

Section 5.0 Safety 306. Comment: This section should be rewritten to reflect cylinder safety, noxious gas safety, CO asphyxiation, or reference to the Source Evaluation Society Safety Manual. Each method should be considered in this light. ( 0035)

Response: We have added precautions concerning cylinder and noxious gas safety to Section 5.0.

Section 6.0 Equipment and Supplies 307. Comment: If you are properly using equipment designed for this application, why would the performance criteria in this method only be met most of the time as opposed to all of the time? What are some examples when the performance criteria are not met when the correct procedures and properly designed equipment are used? Perhaps, Awill@ should be Ashould@ and Amost of the time@ should be deleted. ( 0032)

Response: The statement has been revised to read: AThe performance criteria in this method should be met or exceeded if you are properly using equipment designed for this application.@ 86 308. Comment: A definition of what constitutes dry basis and wet basis is important. A requirement to continuously measure the outlet gas temperature at the coldest point in the heat exchanging vessel of the chiller type gas conditioners should be added. Language should be added that includes dilution extractive and permeation technologies to continuously measure and record the temperature at the coldest in the heat exchanging vessel of the chiller. A number of driers provide continuous dew points substantially below the dew point temperatures called for in the proposed rule. Since dilution systems back calculate the concentration with a dilution ratio, the water fraction will be very significant since it too is multiplied by the dilution ratio. Hot wet instrumentation should also measure and record the water fraction at a similar frequency. Correction of the basis of measurement can then be made to a dry basis at standard conditions as required. At a minimum, the measured dew point or water fraction error can be accounted for in the uncertainty calculation. ( 0023, 0054)

Response: In lieu of listing minimum temperatures and temperature monitoring techniques for specific technologies, we are moving to performance based specifications and are requiring the sample gas be maintained above its dew point prior to analysis.

Section 6.1 What do I need for the measurement system?

309. Comment: This section refers to an example measurement system shown in Figure 7E 1 which is ( a) in direct conflict with the requirements of <IP_ADDRESS>, and ( b) prejudicial to a specific design. The filter media is not included for the bias test. The caption to Figure 7E 1 should be example measurement system. Many other designs are used in practice and will provide equivalent or better performance. For example, a heated head pump can be placed upstream of the moisture removal system or even at the probe outlet so that the entire system is under positive pressure and so that the moisture removal is enhanced. In addition, diagrams of other acceptable systems such as hot wet and dilution sampling systems should be included. The figure indicates a sample filter outside the stack, upstream of the calibration gas 3 way valve. However, the filter can also be located at the probe tip in the stack, or downstream of the 3 way valve but immediately upstream of the moisture removal system. Further, it is very bad practice to have a throttling valve on the pump discharge, and a pump bypass valve is a much better idea. ( 0032, 0038)

Response: Figure 7E 1 has been listed as an example measurement system. To keep the method simple without limiting equipment options, the method notes that other systems such as hot wet and dilution sampling systems are acceptable. The throttling valve on the pump discharge has been redrawn to show a pump bypass valve.

310. Comment: While Section 6.1 mentions that subsections 6.1.1 through 6.1.9 are provided as guidance, this point is not made very plain and I fear may be lost to most readers, especially for wording such as must and subject to approval. I suggest cleaning up the text and moving the bit about guidance to the first paragraph in the section. ( 0022)

Response: Section 6.1 has been revised to clearly note that the example equipment is listed as guidance. 87 311. Comment: I have never seen a design flow rate for a sampling system. They are all home made. Flow is determined by the desired response time and the height of the stack. Item ( 1) in Section 6.1 should read " 5 percent of the initial flow rate." Is design flow rate defined? This is tightening the standard, and does it make any difference? ( 0035, 0043)

Response: Section 6.1 has been clarified to states that " Sample flow rate must be maintained within 10 percent of the flow rate at which the system response time was measured."

312. Comment: There are statements throughout that the probe, sample line, etc., should be heated to at least 140 º C ( 284 º F) or 25 º C ( 77 º F) above the concentration dew point of the sample, whichever is higher, to prevent condensation. We cite a California Energy Commission/ University of California study entitled Quantification of Uncertainties in Continuous Monitoring Systems for Low NOx Emissions from Stationary Sources. The executive summary concluded that " There were no statistical differences observed between any of the sample line test conditions, regardless of material used or operating temperature. The only exception was that, in the presence of ammonia and water, NOx losses increased ( for the lowest NOx input) in the stainless steel line operating at 175 ° C." The test conditions included temperatures at 25, 107, and 175 ° C with various line materials. The study showed that even at relatively low temperatures, little bias was evident and that the only condition that was statistically worse was where the line was heated too hot and it was speculated that additional reactions were taking place. ( 0039)

Response: The language in the methods has been revised to make them technologyneutral The requirement will be to maintain the sample gas above the dew point of the stack gas so that no loss of sample results. This may be done by heating, diluting, drying, desiccating, or a combination thereof, or by other means.

313. Comment: The comments from the Institute of Clean Air Companies ( ICAC) are exactly the same wording as the new proposed rules, and can be interpreted that ICAC members want to sell some new sample lines to companies that already have adequate lines, and that is being endorsed in the rule. ( 0039)

Response: The methods were updated based on information we received from various sources. We incorporated any information we thought was helpful and improving without adding any intended sales benefits to the commenters.

Section 6.1.1 Sample Probe ( Stinger)

314. Comment: ( Stinger) needs some explanatory note. Is Stinger another name for sampling probe? Stinger is not used elsewhere in this method and is not common terminology. ( 0032, 0035)

Response: The use of Astinger@ as another name for the sample probe has been dropped.

315. Comment: Is hastelloy an acceptable alternative to quartz at temperatures greater than 500 ° F? ( 0028) 88 Response: Hastelloy is acceptable at temperatures greater than 500 ° F.

316. Comment: This section refers to the concentration dew point, while Section <IP_ADDRESS> only mentions dew point. Do these terms mean different things? ( 0043)

Response: The two terms mean the same thing and both will be referred to as Adew <EMAIL_ADDRESS> Section <IP_ADDRESS> Particulate Filter 317. Comment: This section requires an in stack or out of stack particulate filter. A particulate filter is not necessary when sampling certain sources, such as gas fired turbines because there is no particulate in the sample stream. Are filters needed for gas turbines? ( 0032, 0035)

Response: The particulate filter requirement may be waived in applications where no significant particulate matter is expected ( e. g., for emission testing of a combustion turbine firing natural gas).

318. Comment: The last sentence of this section requires that the probe filter media be included in the sampling system bias check and be non reactive to the gas being sampled. The EPA should explain the basis for this requirement since we know of no solid phase reactions involving adsorption of NO or NO2. The requirement is appropriate for SO2 sampling systems but not O2 or CO2. If there is not a specific technical basis to support introducing the calibration gas upstream of the filter media for NOx measurements, then this requirement should be deleted ( 0032).

Response: An inappropriately heated filter can trap NO2 on the wet surface. Alkaline moisture would enhance this removal of NO2. The same thing goes for CO2. Therefore, the bias check must include the probe filter.

319. Comment: The section says the filter media must be included in the bias test. Figure 7E 1 is therefore incorrect since the calibration gas injection location is downstream of the heated filter. ( 0026, 0028, 0035, 0054)

Response: Figure 7E 1 has been corrected by placing the calibration gas injection location upstream of the heated filter.

Section 6.1.2 Heated Sample Line 320. Comment: We suggest indicating the Teflon trademark throughout the document. ( 0054)

Response: We no longer use the trademark sign for Teflon or other products that are common and widely used. 89 Section 6.1.3 Sample Lines 321. Comment: This section implies that there is never a need to heat the sample line between the condenser and the analyzers, which is incorrect. The section should state that the temperature must be above the dew point set by the condenser, and in some cases ambient temperature will suffice. ( 0009, 0010)

Response: See response to Comment 105.

322. Comment: Remove the reference to stainless steel and Teflon and change to a material that is non reactive to the gas sampled. ( 0022)

Response: The references to stainless steel has been dropped, and the reference to Teflon have been retained as example material along with a statement that other materials that are nonreactive to the sampled gas are acceptable.

Section 6.1.6 Flow Control/ Gas Manifold 323. Comment: This section is poorly written and thereby imposes unintended and unnecessary design requirements ( i. e., a valve to block the sample gas is not needed for either straight tee or atmospheric vent system calibration designs). Similarly, there is no technical basis to require a back pressure regulator in many acceptable systems ( 0032).

Response: New Section 6.2.6 ( Calibration Gas Manifold) has been reworded to add clarity. The use of a back pressure regulator will be listed as an option, not a requirement. Mention of a valve to block the sample gas flow when introducing calibration gas directly to the analyzer has been dropped.

324. Comment: The current description requires flooding the probe, which wastes expensive Protocol 1 gases. An additional method should be added to perform the sampling system bias check by introducing calibration gases at the calibration valve installed at the outlet of the sampling probe. ( 0013)

Response: The narrative in the new section has been revised to state that calibration gas is normally introduced at the outlet of the probe during the bias check.

325. Comment: Where is the sample flow measured both through the system and to the instrument? ( 0035)

Response: Proposed Section 6.1.6 and final Sections 6.2.6 and 6.2.7 give general design guidance for calibration and sample gas manifolds. Sample flow measurement will depend on the specific measurement system design. 90 326. Comment: The proposed definition does not include dilution systems, and it should be noted that dilution systems use different calibration procedures than direct extractive. Specifically, it is not feasible to introduce source level gas directly to the analyzers. ( 0059)

Response: Section 6.1 states that alternative apparatus and procedures may be used where the sample is diluted prior to analysis.

Section 6.1.7 Sample Gas Manifold 327. Comment: Change Athat does not react with NOx@ to Athat is non reactive to the gas sampled to make it more general.@ ( 0022)

Response: This change has been made.

Section <IP_ADDRESS> Dual Range Analyzers 328. Comment: AManufacturers may certify a gas analyzer with a single large range which can be used with proper data recorders as two separate analyzers if the proper set of calibration gases and the interference tests meet the analyzer calibration error and sampling bias checks.@ This language is unnecessary and confusing. We suggest removing it with the option of adding it to the <EMAIL_ADDRESS>The may certify language could have the very undesirable effect of opening the door to an analyzer certification program similar to that used for ambient instruments. This would stagnate the current advancements being made in the design of source testing instruments. ( 0054, 0059)

Response: This language has been deleted from the method.

Section 6.1.9 Data Recording 329. Comment: The resolution specified is 0.5 percent of span ( the QA table suggests 1 percent of span), while the calibration error specification for the zero gas is " 0.25 percent of upper range limit. If the upper range limit is 5 percent higher than span, then the " 0.25 percent level is below the recorder resolution. This is a direct conflict. ( 0032, 0009, 0030)

Response: The data recorder resolution in the QA table has been corrected to 0.5 percent. The calibration error specification for the low level calibration gas ( which may be a zero gas) is 2 percent of the calibration span or 0.5 ppm.

330. Comment: Regardless of the data recording device, it should be mandatory that the data during the run be recorded in hard copy form for agency personnel to review and validate. This also applies to the calibration error, converter efficiency, stratification, and bias tests. ( 0011)

Response: Section 1.0 notes that you must document your adherence to the specific requirements for equipment, supplies, sample collection and analysis, calculations, and data analysis. 91 331. Comment: Move the resolution specification to the DQO section in Section 1.3, since the resolution of the data recording device is directly tied to the DQO. ( 0022)

Response: We believe it is best to list the resolution specification in this section and not tie it directly to the DQO.

Section 7.1 Calibration Gas 332. Comment: Basing the low level calibration gas concentration on the value of the high level calibration gas is much more confusing than the existing way of using a percent of span. This added confusion will also lead to more mathematical errors, compromising the quality of stack test programs, and possibly invalidating results based on a trivial technicality. ( 0038)

Response: We have made the high level calibration gas synonymous with the calibration span to ensure that all measured data are quality assured when the traditional concentration interval between the high level calibration gas and the span is removed. We do not believe this move adds confusion or leads to mathematical errors but rather increases the defensibility of data collected over the entire measurement range.

Section 7.1.1 Span level Gas 333. Comment: What is the tolerance for readings above the span gas concentration, such as an 86 ppm when using an 85 ppm span gas. The current methods treat this as valid, but it appears there is no allowance for it in the proposed methods. What if an emission spike occurs? Common sense and measurement theory dictates measurements beyond the high calibration gas can be valid. Whether data is potentially valid should be decided by QA in the field, and not subjectively after the fact by a regulatory report reviewer. ( 0028, 0038)

Response: Readings above the calibration span are allowed if the run average is within the calibration span. Run averages that exceed the calibration span due to spikes are normally invalidated. The data quality objectives of a test should be the determining factor for accepting data outside the calibration span.

Section 7.1.3 Low level Gas 334. Comment: Another level of calibration has been added and this does not simplify the methods or reduce costs. We recommend removing all low level calibration requirements for the analyzer error check and the sampling system bias check. ( 0041)

Response: Removing the low level calibration requirements from the calibration error and system bias checks would be reducing the current level of system verification, not removing anything added in the proposal.

335. Comment: Would the use of a 4 point calibration curve, such as that currently required by Method 20, instead of the 3 point curve used in other instrumental methods, improve the data quality? Did EPA consider the possibility of using a 4 point calibration curve similar to 92 Method 20 in all methods with a zero gas and a low level cal gas ( e. g. say 10 to 30 percent of span? What were the findings? ( 0059)

Response: We have not assessed the value of requiring four calibration gases instead of three in this rulemaking. We do not believe the data quality would improve sufficiently to justify the expense of requiring an additional calibration gas.

Section 8.0 Sample Collection, Preservation, Storage, and Transport 336. Comment: The EPA should clarify that all test options, deviations, etc., to the extent they are known in advance, be identified in the test protocol that is typically submitted prior to testing. ( 0038)

Response: The commenter makes a good recommendation which should be followed in all cases where a test protocol is used. However, in keeping to the commitment that test methods be performance based, we hesitate to emphasize the listing of test deviations but rather rely on the performance tests to detect unacceptable variations.

337. Comment: Once response time has been determined, then one times rather than two times the response time should be appropriate to commence measurements. There should be a time limit on the pollutant measurement per point along side the response time criteria ( i. e. either 1 min/ point or 2 times response time, whichever is less restrictive). ( 0030)

Response: After waiting for twice the response time and collecting the sample for the first traverse point, you may move to the next point and continue recording, omitting the requirement to wait for two times the system response time before recording data at the subsequent traverse points.

338. Comment: Under Part 75 regulations, our analyzers have a response time of 5 minutes. Under the proposed method, 2 minutes of sampling preceded by two times response time at 12 points would take more than 144 minutes, which cannot meet the Part 75 requirement of less than 2 hours for a stratification test. We recommend Part 60 revisions be deleted in favor of Part 75 requirements, and comparison on a ppm basis rather than within 5 percent of mean basis. ( 0033)

Response: See the response to Comment 337. With the 5 minute response time and the 12 points described, your sampling time should be about 34 minutes. We have added alternative concentration criteria for comparing the traverse point concentrations for determining stratification.

339. Comment: Note that these methods are to take into account other rules and regulations. These tests are to be used for RATAs ( 21 minutes per run) or for compliance ( 60 180 minutes per run, length of a batch process, etc.), where the pre established run length, not system response time, dictates the length of the test runs. ( 0038) 93 Response: We understand that the methods have sample run times dictated in underlying regulations. Our concern is for collecting representative samples from the source and not samples diluted by sampling line gas Section 8.1.3 Determination of Stratification 340. Comment: Note that stainless steel probes act as a catalyst for CO and NO2 at simple cycle gas turbines and will show stratification even when there is none. ( 0035)

Response: In this case, means of reducing the probe temperature ( such as through watercooling should be considered to reduce the catalytic effects.

Section 8.2.1 Calibration gas verification 341. Comment: Does confirming that the documentation includes all information required by the Protocol mean confirming that the documentation is complete? If so, the first part of the second sentence is redundant ( 0032).

Response: One must ensure that the documentation includes all of the information required by the protocol and that this information passed certification.

342. Comment: The EPA should recommend the tester have copies of calibration gas certification sheets while on site to aid regulators and inspectors in lieu of misreading torn cylinder labels. ( 0038)

Response: A recommendation to have calibration gas certification sheets on site has been added to the methods to aid in on site inspections.

Section 8.2.2 Measurement system preparation 343. Comment: Several commenters thought that restricting measured concentrations between 20 and 100 percent of span was too stringent or unreasonable for the following reasons:

a. The specification does not apply to situations where the span is set relative to a standard according to Section 1.3.1. ( 0012, 0013)

b. Instruments that meet the calibration error or linearity specifications should generate valid data within that range of calibration, and an acceptance of measurements within 5 to 95 or 10 to 90 percent of span is reasonable. ( 0012)

c. When testing new equipment, one cannot know in advance the stack concentrations. ( 0013)

d. Meeting this criterion is not always possible, since there may be dips in emissions below 20 percent. 94 e. The 20 percent limit could not be met for low NOx units with permitted limits below 2 ppm and a Method 7E analyzer set at 10 ppm. ( 0038).

f. This requirement conflicts with Section 1.3.3 in terms of calibrating around the actual concentration instead of the allowable emission. Using the actual concentration is impractical, since it will require having numerous cylinders on hand. ( 0020)

g. What if emissions are non detect, or the lower instrument range is 100 ppm but NOx readings are 10 15 ppm? What if the allowable is 250 ppmv, the analyzer span is 300 ppm, and emission readings are 5 ppmv. Would the tester be required to use a lower range when the only regulatory requirement is to demonstrate compliance? This is not clear throughout the rules. ( 0020, 0030, 0031)