short time period) can be associated with congested, stop-and-go
traffic conditions.
3. Near-Road Environment
    Information in the ISA and other peer-reviewed literature suggest
that concentrations of mobile source pollutants, such as CO, typically
display peak concentrations on or immediately adjacent to roads,
typically producing a gradient in pollutant concentrations where
concentrations decrease with increasing distance from roads (ISA,
section 2.3; ISA, section <IP_ADDRESS>; Baldauf et al., 2008; Clements et
al., 2009; Karner et al., 2010; Zhou and Levy, 2008; Zhu et al., 2002).
CO is emitted by on-road mobile sources, and is not secondarily formed
in the near-road environment like NO2 (which is both
primarily emitted and secondarily formed in the near-road environment).
As a result, the near-road gradient for CO can be quite steep, where
concentrations rapidly decay with increasing distance away from the
road when compared to other mobile source pollutants such as
NO2. Karner et al. (2010), synthesized findings from 41
near-road pollutant monitoring studies ranging from 1978 through June
2008 to advance the understanding of on-road mobile source pollutant
dispersion. They performed two regression analyses, one being a local
regression of background normalized concentrations on distance, and the
second being a local regression of edge [of road] normalized
concentrations on distance. These analyses found CO to have the highest
approximate edge-of-road peaks, as much as 21 times background
concentrations, of all pollutants analyzed, and also showed CO to have
one of the fastest decay rates with increasing distance from the road,
showing as much as a 90 percent drop in concentration 150 meters from
the edge of the road. A key reason in the difference in decay rate with
increasing distance from roads between CO and NO2 is due to
how the two pollutants are introduced into the near-road environment.
CO is a primary emission from motor vehicle fuel combustion, while
NO2 is both emitted as a primary emission and secondarily
formed in the near-road environment. The Integrated Science Assessment
for Oxides of Nitrogen--Health Criteria (NOX ISA; USEPA,
2008d) notes that the direct emission of NO2 from mobile
sources is estimated to be only a few percent of the total
NOX emissions for light duty gasoline vehicles, and from
less than 10 percent up to 70 percent of the total NOX
emission from heavy duty diesel vehicles, depending on the engine, the
use of emission control technologies such as catalyzed diesel
particulate filters (CDPFs), and mode of vehicle operation. Although
much of the NOX emissions are initially in the form of NO,
the rate of conversion of NO to NO2 is generally a rapid
process (i.e., on the order of a minute) (NOX ISA, section
2.2.2). Thus, more of the NO2 in the near-road environment
is a result of secondary formation than from primary emissions, while
CO is almost exclusively a result of direct emissions from tailpipes.
    Overall, the literature suggests that CO concentrations generally
return to near-background levels within a few hundred meters from the
road (Karner et al., 2010; Zhou and Levy, 2007). The actual
concentrations of CO, and other mobile source pollutants such as
NOX and particulate matter, that occur in the near-road
environment, and the rate of decay of those pollutant concentrations
with increasing distance from the road, are dependent on a number of
variables including traffic volume, traffic fleet mix, roadway type,
roadway design, surrounding features, topography (or terrain), and
meteorology (Baldauf et al., 2009; Baldauf et al., 2008; Clements et
al., 2009; Hagler et al., 2010; Heist et al., 2009). EPA notes that
these factors were taken into account in the requirements for the near-
road NO2 monitoring network, promulgated in February 2010
(75 FR 6474), which required near-road NO2 sites to be
selected with consideration given to traffic volume (via use of Annual
Average Daily Traffic [AADT] counts), fleet mix, congestion patterns,
roadway design, terrain, and meteorology.
4. Urban Downtown Areas and Urban Street Canyons
    As noted above in section IV.B.2, increased CO emissions occur
under operating conditions of high acceleration, rapid speed
fluctuations (such as acceleration and deceleration occurring over a
short time period), and increased vehicle loads (ISA, section 3.2.1).
High acceleration and rapid speed fluctuations can be associated with
congested traffic conditions, such as stop-and-go traffic, which can
occur on heavily trafficked roads such as highways, freeways, and along
major arterial roads, and also along roads with multiple intersections
in relatively close proximity to each other. Thus, elevated CO
concentrations, relative to surrounding background concentrations, can
occur not only along heavily trafficked roads but also may be found in
urban downtown areas, where a relatively higher number of roads exist
in an area (high density of roads per unit area) and a relatively
higher density of roadway intersections exist in an area (high roadway
intersection per unit area), which can lead to increased occurrences of
vehicles operating under modes of high acceleration and/or rapid speed
fluctuations. Even though streets in urban downtown areas may not
individually carry as much traffic as larger highways, freeways, or
major arterials, the impact of many relatively smaller streets in close
proximity carrying traffic experiencing periods of high acceleration
and/or rapid speed fluctuations, or congested traffic, may collectively
contribute to elevated CO concentrations in that downtown area.

    In addition to traffic undergoing periods of high acceleration and/
or rapid speed fluctuations or experiencing general traffic congestion,
urban downtown areas often have a number of relatively tall buildings,
typically in close proximity to each other. Such configurations of tall
buildings in relatively close proximity often create urban features
called urban canyons or urban street canyons. Although the term urban
canyon, or urban street canyon, is not formally defined, it can
generally be described as an urban feature, resembling a natural canyon
\59\, where streets or roads exist within dense blocks of relatively
tall buildings. These urban features are of interest because, as noted
in the ISA, recent research by Kaur and Nieuwenhuijsen (2009), and
Carlaw et al. (2007), suggest CO concentrations are related to traffic
volume and fleet mix in the urban street canyon environment, which can
influence potential exposures. EPA has had monitoring requirements in
the past that characterized concentrations of CO in heavily trafficked
downtown streets, i.e. ``urban street canyons,'' (Watkins and Thompson,
2010), and notes such locations may have still have relevance going
forward.
---------------------------------------------------------------------------

    \59\ A natural canyon may be defined as a ``deep narrow valley
with steep sides'' (http://www.merriam-webster.com/dictionary/canyon).
---------------------------------------------------------------------------

5. Meteorological and Topographical Influences
    In 2003, the National Research Council (NRC) of the National
Academies published a document titled Managing Carbon Monoxide
Pollution in Meteorological and Topographical Problem Areas. This
report noted how drastically ambient CO concentrations had dropped
across the country from the 1970s through the early 2000s, and that
some of the remaining areas of the country that continued to have
relatively high concentrations tended to have meteorological and
topographical characteristics that exacerbate pollution. In particular,
meteorological impacts can concentrate pollutant build-up in an area
due to atmospheric inversions and cold temperatures. Atmospheric
inversions essentially prevent pollutant emissions in an area from
dispersing through vertical mixing. As explained by the NRC (NRC,
2003), the extent to which air mixes vertically depends on how the air
temperature changes with altitude. Warm air is less dense than cold air
and thus more buoyant, allowing surface air to mix upward as relatively
warmer air rises in the atmosphere. However, if the vertical
temperature profile is such that temperatures decrease more slowly than
normal, or increase with height, vertical mixing is inhibited.
Inversions can be caused by several different specific phenomena,
including surface based cooling (for example, due to snow on the
ground), due to high altitudes, and sometimes due to warm air advection
at higher altitudes.
    The topographical impacts that can lead to pollutant build-up in an
area are typically due to physical terrain features that may aid in
trapping pollution in an area and/or contribute to meteorological
related inversions. An example of topographical impacts might be an
urban area within a valley, or surrounded on several sides by mountain
ranges. In such a case, pollutant dispersion is inhibited in the
horizontal, with terrain features effectively preventing mixing or
transport of pollution from a given area. Further, in some cases both
meteorological and topographical impacts can combine to exacerbate
pollutant build-up, such as in an area partially surrounded by high
terrain which is also subject to inversions.
    Although there is available information on what can cause increased
potential for air pollutant build-up due to meteorological and
topographical impacts, there are no easily defined or applied criteria
that could be implemented nationally by which all such locations could
be identified. Identification of such locations would require a case-
by-case approach, where localized and detailed information on terrain
and meteorology would be needed, plus an understanding of the types and
amounts of emission sources in or around any particular area.
6. Proposed Changes
    Although EPA is proposing to retain the current 8-hour and 1-hour
CO NAAQS, as discussed above in section II, the Agency is proposing to
revise the requirements for the ambient CO monitoring network to
include a minimum set of monitors to collect data for comparison to the
NAAQS in near-roadway locations where CO emissions associated with
mobile source related activity lead to increased ambient
concentrations. The current network of CO monitors, beyond those at
NCore sites, consists of monitors that were established to meet the
1979 monitoring rule requirements or which were placed by State and
local air monitoring agencies to meet their own needs or objectives.
These additional monitors in the current network are being operated
without being required under EPA monitoring network regulations and as
a result, they do not reflect a national monitoring network design. In
CASAC comments on the second draft REA, the CASAC panel, aware of the
current CO monitoring network configuration, commented on the need to
reconsider CO monitoring network designs, stating that `` * * * the
approach for siting [CO] monitors needs greater consideration. More
extensive coverage may be warranted for areas where concentrations may
be more elevated, such as near roadway locations'' (Brain and Samet,
2010b). Since there is a strong relationship between CO exposures and
mobile source activity, as described in the ISA and REA and summarized
in sections II.D.2 and IV.B.2 above, primarily in the near-road
environment, EPA believes that some CO monitors should be located near
on-road mobile source activity, where ambient concentrations are
expected to be more elevated, as noted by CASAC.
    Accordingly, EPA is proposing to require locating ambient CO
monitors which would produce data for comparison to both the 8-hour and
1-hour NAAQS at a subset of near-road NO2 monitoring
stations, which are required under the Primary National Ambient Air
Quality Standards for Nitrogen Dioxide; Final Rule (75 FR 6474),
codified at 40 CFR part 58, appendix D. This requirement would support
the objective of characterizing ambient conditions at highly trafficked
near-road locations where elevated CO concentrations (relative to
surrounding background concentrations) are expected to occur.
    The EPA is not proposing to require dedicated CO monitoring sites
to characterize area-wide concentrations representing neighborhood and
larger spatial scales. Based on a recent review of the current CO
monitoring network (Watkins and Thompson, 2010), EPA believes that the
required NCore sites and many of the existing monitoring sites in the
network provide data representative of neighborhood and larger spatial
scales. These monitors are useful in providing relative background
concentrations that, when compared to near-road CO monitors, could aid
in the quantification of the near-road gradient of CO in a given urban
area. Between the required NCore sites, and an expectation based on
experience that some number of non-required area-wide sites will
continue to operate in the future, we do not believe it is necessary to
propose a specific area-wide monitoring requirement in this rulemaking.
    EPA believes that the proposed network design which places CO
monitors at a subset of near-road NO2

monitoring stations, as described in detail in the following sections,
will require a relatively modest amount of new resources by State and
local air agencies. Recalling that there were approximately 345 CO
monitors operating in 2009, which were largely discretionary monitors
not operated pursuant to Federal network design requirements, the
Agency believes that a large majority of State and local air agencies
could meet the proposed minimum monitoring requirements by relocating
an existing CO monitor to a near-road NO2 monitoring
station. In some of these cases, the EPA believes that the relocation
of a CO monitor from an existing stand-alone site to a multi-pollutant
near-road NO2 site may also result in additional operational
cost savings as, in some areas, the total number of ambient monitoring
sites for which operational support is needed could be reduced.
    The EPA believes that the proposed requirement for placing CO
monitors at some of the forthcoming near-road NO2 monitoring
stations would provide an important benefit by facilitating the
implementation of a more targeted ambient CO monitoring network that
provides data for comparison to the NAAQS, and is considerably smaller
than the CO network currently in operation. EPA notes that under the
current regulation, the current CO network is subject to a potentially
significant reduction in size (as detailed in Watkins and Thompson,
2010) since non-required CO monitoring stations can be shut down upon
State request, an evaluation of historical data to evaluate
concentrations relative to the NAAQS (per 40 CFR 58.14), and EPA
Regional Administrator approval. The occurrence of such a reduction,
however, would lack the focus and direction needed to ensure retention
of a network with the surveillance aspects essential to supporting the
implementation of the CO NAAQS. In addition to ensuring that an
effective, modestly sized network shall operate in the future, other
benefits of the proposed approach of co-locating required CO monitors
at required near-road NO2 monitoring stations include:
ongoing comparison of data to the NAAQS (for assessing attainment),
providing data that can support health studies, providing data that can
be used in verification of modeling results, and supporting the
implementation of the Agency's multi-pollutant monitoring
objectives.\60\
---------------------------------------------------------------------------

    \60\ The EPA's strategy encouraging multi-pollutant monitoring
is presented most recently in the Ambient Air Monitoring Strategy
for State, Local, and Tribal Air Agencies document published
December 2008 (http://www.epa.gov/ttn/amtic/files/ambient/monitorstrat/AAMS%20for%20SLTs%20%20-%20FINAL%20Dec%202008.pdf).
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a. Monitoring for Carbon Monoxide at Required Near-Road Nitrogen
Dioxide Monitoring Stations
    Traffic volume on urban area roads is much greater than in the more
rural areas of the country, as was noted in the preamble to the final
rule to the NO2 NAAQS (75 FR 6474). The U.S. Department of
Transportation Federal Highway Administration's Status of the Nation's
Highways, Bridges, and Transit: 2008 Conditions and Performance
document (http://www.fhwa.dot.gov/policy/2008cpr/es.htm#c2b) states
that ``while urban mileage constitutes only 25.8 percent of total
(U.S.) mileage, these roads carried 66.3 percent of the 3 trillion
vehicles miles travelled (VMT) in the United States in 2006.'' The
document also states that urban interstate highways made up only 0.8
percent of total (U.S.) mileage but carried 16.3 percent of total VMT.
    The EPA notes that the 2007 American Housing Survey (http://www.census.gov/hhes/www/housing/ahs/ahs07/ahs07.html) estimates that
over 20 million housing units are within 300 feet (~91 meters) of a 4-
lane highway, airport, or railroad. Using the same survey, and
considering that the average number of residential occupants in a
housing unit is approximately 2.25, it is estimated that at least 45
million American citizens live near 4-lane highways, airports, or
railroads. Among these three transportation facilities, roads are the
most pervasive of the three, suggesting that a significant number of
people may live near major roads. Furthermore, the 2008 American Time
Use Survey (http://www.bls.gov/tus/) reported that the average U.S.
civilian spent over 70 minutes traveling per day, and as recognized in
section II.D.2.b, the exposure and dose assessment for this review
found in-vehicle microenvironments to be those with the highest ambient
CO exposures. Additionally, as described in the ISA, PA and the REA,
higher concentrations are reported at locations immediately near or on
roadways as compared to monitors somewhat removed from the roadways
(ISA, section 3.6; PA, section 2.2.1; REA, section 2.7). These
locations capture ambient concentrations that contribute to ambient
exposure concentrations occurring in vehicles. Accordingly, EPA
believes that air pollution monitors near major roads will provide
information pertaining to a significant component of ambient CO
exposure for a large portion of the population that would otherwise not
be available.
    The EPA recognizes the information mentioned above regarding the
dominant role of mobile sources in the national CO emission inventory
(discussed in section IV.B.2 above), findings of the substantial near-
road concentration gradient, with elevated CO concentrations in the
near-road environment compared to relative background concentrations
(discussed in section IV.B.3 above), and the importance of on-road
mobile sources as contributors to ambient CO exposures particularly in
urban areas (REA, section 2.7). We also note that (as referenced above)
CASAC indicated that additional monitoring near roadways may be
warranted, and further stated ``the Panel found in some instances
current networks underestimated carbon monoxide levels near roadways.
Such underestimation is a critical issue * * *'' (Brain and Samet,
2010b). In light of this information, and the fact that we generally
expect the increased levels of ambient CO (and the greatest exposure to
ambient CO) to occur near-roadways, EPA has determined that it is
appropriate to propose requiring CO monitoring near heavily trafficked
roads in urban areas.
    EPA additionally notes that near-road NO2 monitoring
sites will be placed near highly trafficked roads in urban areas, where
elevated CO concentrations due to on-road mobile sources are known to
occur, and that CASAC has recommended that EPA establish a near-road
monitoring network that would include sites with both NO2
and CO monitors (Russell and Samet, 2010). Accordingly, the EPA is
proposing to require CO monitors that will provide data for comparison
to the NAAQS to operate at a subset of required near-road
NO2 monitoring stations, which are required in 40 CFR part
58, appendix D. Specifically, the EPA is proposing that CO monitors be
required in any required near-road NO2 monitoring station in
a core based statistical area (CBSA) with a population of 1,000,000 or
more persons. Based on 2009 U.S. Census estimates (http://www.census.gov) and Federal Highway Administration data (http://www.fhwa.dot.gov/policyinformation/tables/02.cfm) applied to near-road
NO2 network design requirements (noted above), there would
be approximately 77 CO monitoring sites required within near-road
NO2 monitoring stations within 53 CBSAs (including San Juan,
PR).\61\
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    \61\ The near-road NO2 monitoring stations, which are
proposed to house required CO monitors, shall be selected per
considerations spelled out in 40 CFR part 58, Appendix D, section
4.3.2(a)(1), which prescribes site selection by ranking all road
segments in a CBSA by AADT and then identifying a location or
locations adjacent to those highest ranked road segments,
considering fleet mix, roadway design, congestion patterns, terrain,
and meteorology.

---------------------------------------------------------------------------

    In this proposal, EPA concludes that, given the strong relationship
between CO exposures and mobile source activity, placing CO monitors at
near-road NO2 monitoring sites (which will be near highly
trafficked roads in urban areas) is needed to fulfill the ambient CO
monitoring objectives identified in section IV.B above. While having
two monitors within CBSAs of 500,000 or more persons was the historical
monitoring requirement (discussed in detail in Watkins and Thompson,
2010), with declining ambient levels we believe there is less
likelihood for high CO concentrations in relatively smaller (in
population) CBSAs. Accordingly, we believe that proposing to require CO
monitoring only in near-road NO2 monitoring stations in
CBSAs of 1,000,000 or more persons is a reasonable approach that
results in a sufficient number of CO monitors near highly trafficked
roads in urban areas to provide data for supporting the NAAQS, for use
in health studies, for model validation, and to support multi-pollutant
monitoring objectives. The EPA solicits comment upon the proposed
requirement to require CO monitors to operate within a subset of
required near-road NO2 monitoring stations, specifically
those in CBSAs with 1,000,000 or more persons. The EPA solicits comment
on using alternative population thresholds within which CO monitors
might be required to operate in near-road NO2 monitoring
stations, e.g. CBSAs with 750,000 or 500,000 or more persons (which
would require approximately 92 and 126 monitors, respectively), in
light of the proposal to retain the existing CO NAAQS. Finally, the EPA
also solicits comment on the merits of having any minimum near-road
monitoring requirements for the CO monitoring network.
b. Regional Administrator Authority
    The EPA is proposing to include a provision allowing the Regional
Administrators to have the discretion to require monitoring above the
minimum requirements as necessary to address situations where minimum
monitoring requirements are not sufficient to meet monitoring
objectives presented above in section IV.B.1. The EPA recognizes that
minimum monitoring requirements may not always result in a network
sufficient to fulfill one or more data needs or monitoring objectives
for a particular area. An example of when an EPA Regional Administrator
might require an additional monitor above the minimum requirements is
to address a situation where data or other information suggest that a
stationary CO source may be contributing to ground level concentrations
that are approaching or exceeding the NAAQS. A second example of where
an EPA Regional Administrator might require additional monitoring is in
otherwise unmonitored urban downtown areas or urban street canyons (as
discussed above in section IV.B.4), where data or other information
suggest CO concentrations may be approaching or exceeding the NAAQS. A
third example of where an EPA Regional Administrator might require
additional monitoring is in unmonitored areas that are subject to high
ground level CO concentrations particularly due to or enhanced by
topographical and meteorological impacts, as discussed in section
IV.B.5 above. In all cases, the Regional Administrator and the
responsible State or local air monitoring agency should work together
to design and/or maintain the most appropriate CO network to service
monitoring objectives and any particular variety of data needs for an
area.
c. Required Network Implementation
    EPA proposes that state and, when appropriate, local air monitoring
agencies provide a plan for deploying required CO monitors by July 1,
2012. We also propose that the ambient CO monitoring network be
physically established no later than January 1, 2013. These dates
correspond with the implementation schedule of the required near-road
NO2 sites, which are the same locations at which CO monitors
have been proposed to be placed. EPA solicits comment on these proposed
implementation dates.
7. Microscale Carbon Monoxide Monitor Siting Criteria
    Carbon monoxide monitors that are proposed to operate at near-road
NO2 sites would likely be classified as microscale-type
sites, per the general definition of microscale sites in 40 CFR part
58, appendix D, section 1.2. Such CO monitors would be paired with
NO2 monitors required to have inlet probe heights between 2
and 7 meters, and be placed within 50 meters of a target road segment.
However, when the original minimum monitoring requirements for CO were
introduced in the 1979 monitoring rule (44 FR 27571), the siting
criteria codified for microscale CO sites was specifically intended to
account for the installation of a near-road site in street canyon or
street corridor locations. The specific siting criteria for microscale
CO sites, currently located at 40 CFR part 58, appendix E, section 6.2,
and listed in Table E-4 of appendix E, state that ``the inlet probes
for microscale carbon monoxide monitors that are being used to measure
concentrations near roadways must be between 2.5 and 3.5 meters above
ground level.'' Likewise, criteria currently located at 40 CFR part 58,
appendix E, section 6.2, and listed in Table E-4 of appendix E state
that microscale CO monitors are to be between 2 and 10 meters from the
edge of the nearest traffic lane. These siting criteria, originally
developed in 1979, were for use primarily in the urban downtown and
urban street canyon environment. In that type of urban environment,
such specific and relatively tight siting criteria were, and still are,
appropriate since there is often little space within which ambient air
monitoring inlets can be accommodated due to the typical dense
configuration of buildings. However, outside of the urban downtown and
urban street canyon environment, such criteria may be less applicable,
considering site placement logistics and site safety for monitoring
near the major highways, freeways, interstates, and major arterials
that carry so much of today's urban traffic volume.
    As noted above, the intent of existing microscale CO siting
criteria reflects the historical intent of monitoring in urban downtown
areas and urban street canyons. Since EPA is proposing that CO monitors
be required to operate at a subset of near-road NO2 sites to
characterize roadway pollutant concentrations the majority of which are
not anticipated to be in urban street canyons, EPA has revisited the
appropriateness of the existing microscale CO siting requirement,
particularly for near-road sites that exist outside of the downtown
urban areas and urban street canyons. EPA consulted on this issue with
the CASAC Ambient Air Monitoring and Methods Subcommittee (CASAC-AAMMS)
in September, 2010. Specifically, EPA requested feedback on whether it
would be appropriate to revise existing microscale CO siting criteria
to match those of near-road NO2 monitors and microscale
PM2.5 monitors. In their response to EPA, the CASAC-AAMMS
recommended ``that sampling criteria for CO and other monitors at sites
installed to monitor [at] near-road NO2 [sites] match those
for NO2.'' The CASAC-

AAMMS also noted that ``sampling configurations of existing microscale
CO monitors should be assessed in terms of their own sampling
objectives, and need not necessarily conform to those of near-road
NO2 monitors'' (Russell and Samet, 2010).
    Based in part on the CASAC-AAMMS comments above, EPA believes that
it is appropriate to revise the existing siting criteria for microscale
CO monitors to encompass both the current criteria, which are still
appropriate when monitoring in the urban downtown and/or urban street
canyon environment, as well as the criteria for near-road
NO2 sites. Therefore, EPA is proposing that microscale CO
siting criteria for probe height and horizontal spacing be changed to
match those of near-road NO2 sites as prescribed in 40 CFR
part 58 appendix E, sections 2, 4(d), 6.4(a), and Table E-4.
Specifically, EPA proposes to allow microscale CO monitor inlet probes
to be between 2 and 7 meters above the ground; that CO monitor inlet
probes be placed so they have an unobstructed air flow, where no
obstacles exist at or above the height of the monitor probe, between
the monitor probe and the outside nearest edge of the traffic lanes of
the target road segment; and that the CO monitor inlet probe shall be
as near as practicable to the outside nearest edge of the traffic lanes
of the target road segment, but shall not be located at a distance
greater than 50 meters in the horizontal from the outside nearest edge
of the traffic lanes of the target road segment.
    These proposed siting criteria encompass, or bracket, the current
allowable vertical and horizontal spacing criteria for microscale CO
sites, which will allow current microscale CO sites to continue to meet
siting criteria. EPA believes the proposed revision to the microscale
CO siting criteria presented above will allow States to meet siting
criteria while co-locating required microscale CO monitors with
required near-road NO2 monitors near heavily trafficked
roads outside of urban downtown areas and urban street canyons. EPA
solicits comment upon the revised CO siting requirements proposed
above. The Agency also solicits comment upon whether it should create
two distinct sets of siting criteria for microscale CO monitoring. One
set of siting criteria would be those proposed above, while the second
set would be the current siting criteria, but directed specifically to
apply to existing or new microscale CO monitoring sites located in
downtown urban areas and urban street canyons.

V. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), this
action is a ``significant regulatory action'' because it was deemed to
``raise novel legal or policy issues.'' Accordingly, EPA submitted this
action to the Office of Management and Budget (OMB) for review under
Executive Order 12866 and any changes made in response to OMB
recommendations have been documented in the docket for this action.

B. Paperwork Reduction Act

    The information collection requirements in this final rule have
been submitted for approval to the Office of Management and Budget
(OMB) under the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. The
information collection requirements are not enforceable until OMB
approves them. The Information Collection Request (ICR) document
prepared by EPA for these revisions to part 58 has been assigned EPA
ICR number 0940.23.
    The information collected under 40 CFR part 53 (e.g., test results,
monitoring records, instruction manual, and other associated
information) is needed to determine whether a candidate method intended
for use in determining attainment of the National Ambient Air Quality
Standards (NAAQS) in 40 CFR part 50 will meet comparability
requirements for designation as a Federal reference method (FRM) or
Federal equivalent method (FEM). We do not expect the number of FRM or
FEM determinations to increase over the number that is currently used
to estimate burden associated with CO FRM/FEM determinations provided
in the current ICR for 40 CFR part 53 (EPA ICR numbers 0940.23). As
such, no change in the burden estimate for 40 CFR part 53 has been made
as part of this rulemaking.
    The information collected and reported under 40 CFR part 58 is
needed to determine compliance with the NAAQS, to characterize air
quality and associated health impacts, to develop emissions control
strategies, and to measure progress for the air pollution program. The
amendments would revise the technical requirements for CO monitoring
sites, require the relocation or siting of ambient CO air monitors, and
the reporting of the collected ambient CO monitoring data to EPA's Air
Quality System (AQS). The annual average reporting burden for the
collection under 40 CFR part 58 (averaged over the first 3 years of
this ICR) for a network of 311 CO monitors is $7,235,483. Burden is
defined at 5 CFR 1320.3(b). State, local, and Tribal entities are
eligible for State assistance grants provided by the Federal government
under the CAA which can be used for monitors and related activities.
    An agency may not conduct or sponsor, and a person is not required
to respond to, a collection of information unless it displays a
currently valid OMB control number. The OMB control numbers for EPA's
regulations in 40 CFR are listed in 40 CFR part 9.
    To comment on the Agency's need for this information, the accuracy
of the provided burden estimates, and any suggested methods for
minimizing respondent burden, EPA has established a public docket for
this rule, which includes this ICR, under Docket ID number EPA-HQ-OAR-
2008-0015. Submit any comments related to the ICR to EPA and OMB. See
ADDRESSES section at the beginning of this notice for where to submit
comments to EPA. Send comments to OMB at the Office of Information and
Regulatory Affairs, Office of Management and Budget, 725 17th Street,
NW, Washington, DC 20503, Attention: Desk Office for EPA. Since OMB is
required to make a decision concerning the ICR between 30 and 60 days
after February 11, 2011, a comment to OMB is best assured of having its
full effect if OMB receives it March 14, 2011. The final rule will
respond to any OMB or public comments on the information collection
requirements contained in this proposal.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency
to prepare a regulatory flexibility analysis of any rule subject to
notice and comment rulemaking requirements under the Administrative
Procedure Act or any other statute unless the agency certifies that the
rule will not have a significant economic impact on a substantial
number of small entities. Small entities include small businesses,
small organizations, and small governmental jurisdictions.
    For purposes of assessing the impacts of today's proposed rule on
small entities, small entity is defined as: (1) A small business that
is a small industrial entity as defined by the Small Business
Administration's (SBA) regulations at 13 CFR 121.201; (2) a small
governmental jurisdiction that is a government of a city, county, town,
school district or special district with a population of less than
50,000; and (3) a small

organization that is any not-for-profit enterprise which is
independently owned and operated and is not dominant in its field.
    After considering the economic impacts of this proposed rule on
small entities, I certify that this action will not have a significant
economic impact on a substantial number of small entities. This
proposed rule will not impose any requirements on small entities.
Rather, this rule proposes to retain existing national standards for
allowable concentrations of CO in ambient air as required by section
109 of the CAA. See also American Trucking Associations v. EPA. 175 F.
3d at 1044-45 (NAAQS do not have significant impacts upon small
entities because NAAQS themselves impose no regulations upon small
entities). Similarly, the proposed amendments to 40 CFR part 58 address
the requirements for States to collect information and report
compliance with the NAAQS and will not impose any requirements on small
entities. We continue to be interested in the potential impacts of the
proposed rule on small entities and welcome comments on issues related
to such impacts.

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public
Law 104-4, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and Tribal
governments and the private sector. Unless otherwise prohibited by law,
under section 202 of the UMRA, EPA generally must prepare a written
statement, including a cost-benefit analysis, for proposed and final
rules with ``Federal mandates'' that may result in expenditures to
State, local, and Tribal governments, in the aggregate, or to the
private sector, of $100 million or more in any one year (adjusted for
inflation). Before promulgating an EPA rule for which a written
statement is required under section 202, section 205 of the UMRA
generally requires EPA to identify and consider a reasonable number of
regulatory alternatives and to adopt the least costly, most cost-
effective or least burdensome alternative that achieves the objectives
of the rule. The provisions of section 205 do not apply when they are
inconsistent with applicable law. Moreover, section 205 allows EPA to
adopt an alternative other than the least costly, most cost-effective
or least burdensome alternative if the Administrator publishes with the
final rule an explanation why that alternative was not adopted. Before
EPA establishes any regulatory requirements that may significantly or
uniquely affect small governments, including Tribal governments, it
must have developed under section 203 of the UMRA a small government
agency plan. The plan must provide for notifying potentially affected
small governments, enabling officials of affected small governments to
have meaningful and timely input in the development of EPA regulatory
proposals with significant Federal intergovernmental mandates, and
informing, educating, and advising small governments on compliance with
the regulatory requirements.
    This action is not subject to the requirements of sections 202 and
205 of the UMRA. EPA has determined that this proposed rule does not
contain a Federal mandate that may result in expenditures of $100
million or more for State, local, and Tribal governments, in the
aggregate, or the private sector in any one year (adjusted for
inflation). This rule proposes to retain existing national ambient air
quality standards for carbon monoxide. The expected costs associated
with the monitoring requirements are described in EPA's ICR document,
but those costs are expected to be well less than $100 million
(adjusted for inflation) in the aggregate for any year. Furthermore, as
indicated previously, in setting a NAAQS, EPA cannot consider the
economic or technological feasibility of attaining ambient air quality
standards.
    EPA has determined that this proposed rule contains no regulatory
requirements that might significantly or uniquely affect small
governments because it imposes no enforceable duty on any small
governments. Therefore, this rule is not subject to the requirements of
section 203 of the UMRA.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have
substantial direct effects on the States, on the relationship between
the national government and the States, or on the distribution of power
and responsibilities among the various levels of government, as
specified in Executive Order 13132. The rule does not alter the
relationship between the Federal government and the States regarding
the establishment and implementation of air quality improvement
programs as codified in the CAA. Under section 109 of the CAA, EPA is
mandated to establish and review NAAQS; however, CAA section 116
preserves the rights of States to establish more stringent requirements
if deemed necessary by a State. Furthermore, this proposed rule does
not impact CAA section 107 which establishes that the States have
primary responsibility for implementation of the NAAQS. Finally, as
noted in section D (above) on UMRA, this rule does not impose
significant costs on State, local, or Tribal governments or the private
sector. Thus, Executive Order 13132 does not apply to this rule.
    However, as also noted in section D (above) on UMRA, EPA recognizes
that States will have a substantial interest in this rule, including
the proposed air quality surveillance requirements of 40 CFR part 58.
Therefore, in the spirit of Executive Order 13132, and consistent with
EPA policy to promote communications between EPA and State and local
governments, EPA specifically solicits comment on this proposed rule
from State and local officials.

F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    This action does not have Tribal implications, as specified in
Executive Order 13175 (65 FR 67249, November 9, 2000). It does not have
a substantial direct effect on one or more Indian Tribes, since Tribes
are not obligated to adopt or implement any NAAQS. Thus, Executive
Order 13175 does not apply to this rule.

G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks

    This action is not subject to EO 13045 (62 FR 19885, April 23,
1997) because it is not economically significant as defined in EO
12866, and because the Agency does not believe the environmental health
or safety risks addressed by this action present a disproportionate
risk to children. This action's health and risk assessments are
described in sections II.C and II.D.2.b.
    The public is invited to submit comments or identify peer-reviewed
studies and data that assess effects of early life exposures to CO.

H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution or Use

    This action is not a ``significant energy action'' as defined in
Executive Order 13211, (66 FR 28355 (May 22, 2001)) because it is not
likely to have a significant adverse effect on the supply,
distribution, or use of energy. The rule concerns the review of the
NAAQS for CO. The rule does not prescribe specific pollution control
strategies by which these ambient standards will be met. Such
strategies are developed by States on a case-by-case basis, and EPA
cannot predict whether the control options selected by States will
include

regulations on energy suppliers, distributors, or users.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement
Act of 1995 (NTTAA), Public Law 104- 113, section 12(d) (15 U.S.C. 272
note) directs EPA to use voluntary consensus standards in its
regulatory activities unless to do so would be inconsistent with
applicable law or otherwise impractical. Voluntary consensus standards
are technical standards (e.g., materials specifications, test methods,
sampling procedures, and business practices) that are developed or
adopted by voluntary consensus standards bodies. The NTTAA directs EPA
to provide Congress, through OMB, explanations when the Agency decides
not to use available and applicable voluntary consensus standards.
    This proposed rulemaking involves technical standards with regard
to ambient monitoring of CO. We have not identified any potentially
applicable voluntary consensus standards that would adequately
characterize ambient CO concentrations for the purposes of determining
compliance with the CO NAAQS and none have been brought to our
attention.
    EPA welcomes comments on this aspect of the proposed rule, and
specifically invites the public to identify potentially applicable
voluntary consensus standards and to explain why such standards should
be used in the regulation.

J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898 (59 FR 7629 (Feb. 16, 1994)) establishes
Federal executive policy on environmental justice. Its main provision
directs Federal agencies, to the greatest extent practicable and
permitted by law, to make environmental justice part of their mission
by identifying and addressing, as appropriate, disproportionately high
and adverse human health or environmental effects of their programs,
policies, and activities on minority populations and low-income
populations in the United States.
    EPA has determined that this proposed rule will not have
disproportionately high and adverse human health or environmental
effects on minority or low-income populations because it does not
affect the level of protection provided to human health or the
environment. The action proposed in this notice is to retain without
revision the existing NAAQS for CO. Therefore this action will not
cause increases in source emissions or air concentrations.

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at: http://www.epa.gov/ttn/naaqs/standards/co/s_co_cr_pa.html
U.S. Environmental Protection Agency. (2010f) Analyzer Use in U.S.
Monitoring Networks. Spreadsheet of air monitoring method
utilization in U.S. monitoring networks by year. Office of Air
Quality Planning and Standards.
U.S. Environmental Protection Agency. (2010g) Modern CO Instrument
Performance Data. Spreadsheet of performance data for existing FRM
analyzers. Office of Research and Development.
Watkins N. and Thompson R. (2010) CO Monitoring Network Background
and Review. Memorandum to the Carbon Monoxide NAAQS Review Docket.
EPA-HQ-OAR-2008-0015.
Wellenius G.A.; Bateson T.F.; Mittleman M.A.; Schwartz J. (2005)
Particulate air pollution and the rate of hospitalization for
congestive heart failure among Medicare beneficiaries in Pittsburgh,
Pennsylvania. Am J Epidemiol 161:1030-1036.
WHO (2008). Harmonization Project Document No. 6. Part 1: Guidance
document on characterizing and communicating uncertainty in exposure
assessment. Available at: http://www.who.int/ipcs/methods/harmonization/areas/exposure/en/.
Zanobetti A. and Schwartz J. (2001) Are diabetics more susceptible
to the health effects of airborne particles? Am J Respir. Crit. Care
Med. 164:831-833.
Zhou, Y and Levy J.I. (2007) Factors influencing the spatial extent
of mobile source air pollution impacts: A meta-analysis. BMC Public
Health, 7:89.
Zhu Y.; Hinds W.C.; Kim S.; Shen S.; Sioutas C. (2002) Study of
ultrafine particles near a major highway with heavy-duty diesel
traffic. Atmos Environ, 36: 4323-4335.

List of Subjects

40 CFR Part 50

    Environmental protection, Air pollution control, Carbon monoxide,
Lead, Nitrogen dioxide, Ozone, Particulate matter, Sulfur oxides.

40 CFR Part 53

    Environmental protection, Administrative practice and procedure,
Air pollution control, Intergovernmental relations, Reporting and
recordkeeping requirements.

40 CFR Part 58

    Environmental protection, Administrative practice and procedure,
Air pollution control, Intergovernmental relations, Reporting and
recordkeeping requirements.

    Dated: January 28, 2011.
Lisa P. Jackson,
Administrator.

    For the reasons stated in the preamble, title 40, chapter I of the
Code of Federal Regulations is proposed to be amended as follows:

PART 50--NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY
STANDARDS

    1. The authority citation for part 50 continues to read as follows:

    Authority:  42 U.S.C. 7401, et seq.

    2. Appendix C to Part 50 is revised to read as follows:

Appendix C to Part 50--Measurement Principle and Calibration Procedure
for the Measurement of Carbon Monoxide in the Atmosphere (Non-
Dispersive Infrared Photometry)

1.0 Applicability

    1.1 This non-dispersive infrared photometry (NDIR) Federal
Reference Method (FRM) provides measurements of the concentration of
carbon monoxide (CO) in ambient air for determining compliance with the
primary and secondary National Ambient Air Quality Standards (NAAQS)
for CO as specified in Sec.  50.8 of this chapter. The method is
applicable to continuous sampling and measurement of ambient CO
concentrations suitable for determining 1-hour or longer average
measurements. The method may also provide measurements of shorter
averaging times, subject to specific analyzer performance limitations.
Additional CO

monitoring quality assurance procedures and guidance are provided in
part 58, appendix A, of this chapter and in reference 1 of this
appendix C.

2.0 Measurement Principle

    2.1 Measurements of CO in ambient air are based on automated
measurement of the absorption of infrared radiation by CO in an ambient
air sample drawn into an analyzer employing non-wavelength-dispersive,
infrared photometry (NDIR method). Infrared energy from a source in the
photometer is passed through a cell containing the air sample to be
analyzed, and the quantitative absorption of energy by CO in the sample
cell is measured by a suitable detector. The photometer is sensitized
specifically to CO by employing CO gas in a filter cell in the optical
path, which, when compared to a differential optical path without a CO
filter cell, limits the measured absorption to one or more of the
characteristic wavelengths at which CO strongly absorbs. However, to
meet measurement performance requirements, various optical filters,
reference cells, rotating gas filter cells, dual-beam configurations,
moisture traps, or other means may also be used to further enhance
sensitivity and stability of the photometer and to minimize potential
measurement interference from water vapor, carbon dioxide
(CO2), or other species. Also, various schemes may be used
to provide a suitable zero reference for the photometer, and optional
automatic compensation may be provided for the actual pressure and
temperature of the air sample in the measurement cell. The measured
infrared absorption, converted to a digital reading or an electrical
output signal, indicates the measured CO concentration.
    2.2 The measurement system is calibrated by referencing the
analyzer's CO measurements to CO concentration standards traceable to a
National Institute of Standards and Technology (NIST) primary standard
for CO, as described in the associated calibration procedure specified
in section 4 of this reference method.
    2.3 An analyzer implementing this measurement principle will be
considered a reference method only if it has been designated as a
reference method in accordance with part 53 of this chapter.
    2.4 Sampling considerations. The use of a particle filter in the
sample inlet line of a CO FRM analyzer is optional and left to the
discretion of the user unless such a filter is specified or recommended
by the analyzer manufacturer in the analyzer's associated operation or
instruction manual.

3.0 Interferences

    3.1 The NDIR measurement principle is potentially susceptible to
interference from water vapor and CO2, which have some
infrared absorption at wavelengths in common with CO and normally exist
in the atmosphere. Various instrumental techniques can be used to
effectively minimize these interferences.

4.0 Calibration Procedures

    4.1 Principle. Either of two methods may be selected for dynamic
multipoint calibration of FRM CO analyzers, using test gases of
accurately known CO concentrations obtained from one or more compressed
gas cylinders certified as CO transfer standards:
    4.1.1 Dilution method: A single certified standard cylinder of CO
is quantitatively diluted as necessary with zero air to obtain the
various calibration concentration standards needed.
    4.1.2 Multiple-cylinder method: Multiple, individually certified
standard cylinders of CO are used for each of the various calibration
concentration standards needed.
    4.1.3 Additional information on calibration may be found in Section
12 of reference 1.
    4.2 Apparatus. The major components and typical configurations of
the calibration systems for the two calibration methods are shown in
Figures 1 and 2. Either system may be made up using common laboratory
components, or it may be a commercially manufactured system. In either
case, the principal components are as follows:
    4.2.1 CO standard gas flow control and measurement devices (or a
combined device) capable of regulating and maintaining the standard gas
flow rate constant to within  2 percent and measuring the
gas flow rate accurate to within  2 percent, properly
calibrated to a NIST-traceable standard.
    4.2.2 For the dilution method (Figure 1), dilution air flow control
and measurement devices (or a combined device) capable of regulating
and maintaining the air flow rate constant to within  2
percent and measuring the air flow rate accurate to within
2 percent, properly calibrated to a NIST-traceable standard.
    4.2.3 Standard gas pressure regulator(s) for the standard CO
cylinder(s), suitable for use with a high-pressure CO gas cylinder and
having a non-reactive diaphragm and internal parts and a suitable
delivery pressure.
    4.2.4 Mixing chamber for the dilution method, of an inert material
and of proper design to provide thorough mixing of CO standard gas and
diluent air streams.
    4.2.5 Output sampling manifold, constructed of an inert material
and of sufficient diameter to ensure an insignificant pressure drop at
the analyzer connection. The system must have a vent designed to ensure
nearly atmospheric pressure at the analyzer connection port and to
prevent ambient air from entering the manifold.
    4.3 Reagents.
    4.3.1 CO gas concentration transfer standard(s) of CO in air,
containing an appropriate concentration of CO suitable for the selected
operating range of the analyzer under calibration and traceable to a
NIST standard reference material (SRM). If the CO analyzer has
significant sensitivity to CO2, the CO standard(s) should
also contain 350 to 400 ppm CO2 to replicate the typical
CO2 concentration in ambient air. However, if the zero air
dilution ratio used for the dilution method is not less than 100:1 and
the zero air contains ambient levels of CO2, then the CO
standard may be contained in nitrogen and need not contain
CO2.
    4.3.2 For the dilution method, clean zero air, free of contaminants
that could cause a detectable response on or a change in sensitivity of
the CO analyzer. The zero air should contain < 0.1 ppm CO.
    4.4 Procedure Using the Dilution Method.
    4.4.1 Assemble or obtain a suitable dynamic dilution calibration
system such as the one shown schematically in Figure 1. Generally, all
calibration gases including zero air must be introduced into the sample
inlet of the analyzer. However, if the analyzer has special, approved
zero and span inlets and automatic valves to specifically allow
introduction of calibration standards at near atmospheric pressure,
such inlets may be used for calibration in lieu of the sample inlet.
For specific operating instructions, refer to the manufacturer's
manual.
    4.4.2 Ensure that there are no leaks in the calibration system and
that all flowmeters are properly and accurately calibrated, under the
conditions of use, if appropriate, against a reliable volume or flow
rate standard such as a soap-bubble meter or wet-test meter traceable
to a NIST standard. All volumetric flow rates should be corrected to
the same temperature and pressure such as 298.15 K (25 [deg]C) and 760
mm Hg (101 kPa), using a correction formula such as the following:

[GRAPHIC] [TIFF OMITTED] TP11FE11.154

Where:

Fc = corrected flow rate (L/min at 25 [deg]C and 760 mm Hg),
Fm = measured flow rate (at temperature Tm and pressure Pm),
Pm = measured pressure in mm Hg (absolute), and
Tm = measured temperature in degrees Celsius.

    4.4.3 Select the operating range of the CO analyzer to be
calibrated.
    4.4.4 Connect the inlet of the CO analyzer to the output-sampling
manifold of the calibration system.
    4.4.5 Adjust the calibration system to deliver zero air to the
output manifold. The total air flow must exceed the total demand of the
analyzer(s) connected to the output manifold to ensure that no ambient
air is pulled into the manifold vent. Allow the analyzer to sample zero
air until a stable response is obtained. After the response has
stabilized, adjust the analyzer zero reading.
    4.4.6 Adjust the zero air flow rate and the CO gas flow rate from
the standard CO cylinder to provide a diluted CO concentration of
approximately 80 percent of the measurement upper range limit (URL) of
the operating range of the analyzer. The total air flow rate must
exceed the total demand of the analyzer(s) connected to the output
manifold to ensure that no ambient air is pulled into the manifold
vent. The exact CO concentration is calculated from:
[GRAPHIC] [TIFF OMITTED] TP11FE11.155

Where:

[CO]OUT = diluted CO concentration at the output manifold (ppm),
[CO]STD = concentration of the undiluted CO standard (ppm),
FCO = flow rate of the CO standard (L/min), and
FD = flow rate of the dilution air (L/min).

    Sample this CO concentration until a stable response is obtained.
Adjust the analyzer span control to obtain the desired analyzer
response reading equivalent to the calculated standard concentration.
If substantial adjustment of the analyzer span control is required, it
may be necessary to recheck the zero and span adjustments by repeating
steps 4.4.5 and 4.4.6. Record the CO concentration and the analyzer's
final response.
    4.4.7 Generate several additional concentrations (at least three
evenly spaced points across the remaining scale are suggested to verify
linearity) by decreasing FCO or increasing FD. Be sure the total flow
exceeds the analyzer's total flow demand. For each concentration
generated, calculate the exact CO concentration using equation (2).
Record the concentration and the analyzer's stable response for each
concentration. Plot the analyzer responses (vertical or y-axis) versus
the corresponding CO concentrations (horizontal or x-axis). Calculate
the linear regression slope and intercept of the calibration curve and
verify that no point deviates from this line by more than 2 percent of
the highest concentration tested.
    4.5 Procedure Using the Multiple-Cylinder Method. Use the procedure
for the dilution method with the following changes:
    4.5.1 Use a multi-cylinder, dynamic calibration system such as the
typical one shown in Figure 2.
    4.5.2 The flowmeter need not be accurately calibrated, provided the
flow in the output manifold can be verified to exceed the analyzer's
flow demand.
    4.5.3 The various CO calibration concentrations required in Steps
4.4.5, 4.4.6, and 4.4.7 are obtained without dilution by selecting zero
air or the appropriate certified standard cylinder.
    4.6 Frequency of Calibration. The frequency of calibration, as well
as the number of points necessary to establish the calibration curve
and the frequency of other performance checking, will vary by analyzer.
However, the minimum frequency, acceptance criteria, and subsequent
actions are specified in reference 1, appendix D, ``Measurement Quality
Objectives and Validation Template for CO'' (page 5 of 30). The user's
quality control program should provide guidelines for initial
establishment of these variables and for subsequent alteration as
operational experience is accumulated. Manufacturers of CO analyzers
should include in their instruction/operation manuals information and
guidance as to these variables and on other matters of operation,
calibration, routine maintenance, and quality control.

5.0 Reference

    1. QA Handbook for Air Pollution Measurement Systems--Volume II.
Ambient Air Quality Monitoring Program. U.S. EPA. EPA-454/B-08-003
(2008).
BILLING CODE 6560-50-P

[GRAPHIC] [TIFF OMITTED] TP11FE11.138

[GRAPHIC] [TIFF OMITTED] TP11FE11.139

BILLING CODE 6560-50-C

PART 53--AMBIENT AIR QUALITY REFERENCE AND EQUIVALENT METHODS

    3. The authority citation for part 53 continues to read as follows:

    Authority:  42 U.S.C. 7401, et seq.

    4. Subpart B of Part 53 is revised to read as follows:
Subpart B--Procedures for Testing Performance Characteristics of
Automated Methods for SO[bdi2], CO, O[bdi3], and NO[bdi2]
Sec.
53.20 General provisions.
53.21 Test conditions.
53.22 Generation of test atmospheres.
53.23 Test procedure.
Appendix A to Subpart B--Optional Forms for Reporting Test Results

Subpart B--Procedures for Testing Performance Characteristics of
Automated Methods for SO[bdi2], CO, O[bdi3], and NO[bdi2]

Sec.  53.20  General provisions.

    (a) The test procedures given in this subpart shall be used to test
the performance of candidate automated methods against the performance
requirement specifications given in

table B-1. A test analyzer representative of the candidate automated
method must exhibit performance better than, or not outside, the
specified limit or limits for each such performance parameter specified
(except range) to satisfy the requirements of this subpart. Except as
provided in paragraph (b) of this section, the measurement range of the
candidate method must be the standard range specified in table B-1 to
satisfy the requirements of this subpart.
    (b) Measurement ranges. For a candidate method having more than one
selectable measurement range, one range must be the standard range
specified in table B-1, and a test analyzer representative of the
method must pass the tests required by this subpart while operated in
that range.
    (1) Higher ranges. The tests may be repeated for one or more higher
(broader) ranges (i.e., ranges extending to higher concentrations) than
the standard range specified in table B-1, provided that the range does
not extend to concentrations more than four times the upper range limit
of the standard range specified in table B-1. For such higher ranges,
only the tests for range (calibration), noise at 80% of the upper range
limit, and lag, rise and fall time are required to be repeated. For the
purpose of testing a higher range, the test procedure of Sec.  53.23(e)
may be abridged to include only those components needed to test lag,
rise and fall time.
    (2) Lower ranges. The tests may be repeated for one or more lower
(narrower) ranges (i.e., ones extending to lower concentrations) than
the standard range specified in table B-1. For methods for some
pollutants, table B-1 specifies special performance limit requirements
for lower ranges. If special low-range performance limit requirements
are not specified in table B-1, then the performance limit requirements
for the standard range apply. For lower ranges for any method, only the
tests for range (calibration), noise at 0% of the measurement range,
lower detectable limit, (and nitric oxide interference for
SO2 UVF methods) are required to be repeated, provided the
tests for the standard range shows the applicable limit specifications
are met for the other test parameters.
    (3) If the tests are conducted and passed only for the specified
standard range, any FRM or FEM determination with respect to the method
will be limited to that range. If the tests are passed for both the
specified range and one or more higher or lower ranges, any such
determination will include the additional higher or lower range(s) as
well as the specified standard range. Appropriate test data shall be
submitted for each range sought to be included in a FRM or FEM method
determination under this paragraph (b).
    (c) For each performance parameter (except range), the test
procedure shall be initially repeated seven (7) times to yield 7 test
results. Each result shall be compared with the corresponding
performance limit specification in table B-1; a value higher than or
outside the specified limit or limits constitutes a failure. These 7
results for each parameter shall be interpreted as follows:
    (1) Zero (0) failures: The candidate method passes the test for the
performance parameter.
    (2) Three (3) or more failures: The candidate method fails the test
for the performance parameter.
    (3) One (1) or two (2) failures: Repeat the test procedures for the
performance parameter eight (8) additional times yielding a total of
fifteen (15) test results. The combined total of 15 test results shall
then be interpreted as follows:
    (i) One (1) or two (2) failures: The candidate method passes the
test for the performance parameter.
    (ii) Three (3) or more failures: The candidate method fails the
test for the performance parameter.
    (d) The tests for zero drift, span drift, lag time, rise time, fall
time, and precision shall be carried out in a single integrated
procedure conducted at various line voltages and ambient temperatures
specified in Sec.  53.23(e). A temperature-controlled environmental
test chamber large enough to contain the test analyzer is recommended
for this test. The tests for noise, lower detectable limit, and
interference equivalent shall be conducted at any ambient temperature
between 20 [deg]C and 30 [deg]C, at any normal line voltage between 105
and 125 volts, and shall be conducted such that not more than three (3)
test results for each parameter are obtained in any 24-hour period.
    (e) If necessary, all measurement response readings to be recorded
shall be converted to concentration units or adjusted according to the
calibration curve constructed in accordance with Sec.  53.21(b).
    (f) All recorder chart tracings (or equivalent data plots),
records, test data and other documentation obtained from or pertinent
to these tests shall be identified, dated, signed by the analyst
performing the test, and submitted.

    Note to Sec.  53.20:  Suggested formats for reporting the test
results and calculations are provided in Figures B-2, B-3, B-4, B-5,
and B-6 in appendix A to this subpart. Symbols and abbreviations
used in this subpart are listed in table B-5 of appendix A to this
subpart.

                                            Table B-1--Performance Limit Specifications for Automated Methods
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                          SO2                           CO
                                                                 --------------------    O3    --------------------    NO2
         Performance parameter                   Units 1                      Lower     (Std.               Lower     (Std.      Definitions and test
                                                                    Std.     range 2   range)     Std.     range 2   range)           procedures
                                                                   range 3      3                range 3      3
--------------------------------------------------------------------------------------------------------------------------------------------------------
1. Range..............................  ppm.....................     0-0.5     < 0.5     0-0.5      0-50      < 50     0-0.5  Sec. 53.23(a).
2. Noise..............................  ppm.....................     0.001    0.0005     0.005       0.2       0.1     0.005  Sec. 53.23(b).
3. Lower detectable limit.............  ppm.....................     0.002     0.001     0.010       0.4       0.2     0.010  Sec. 53.23(c).
4. Interference equivalent:
    Each interferent..................  ppm.....................        minus>    minus>    minus>    minus>    minus>
                                                                     0.005     0.005      0.02       1.0       0.5      0.02
    Total, all interferents...........  ppm.....................  ........  ........      0.06  ........  ........      0.04  Sec. 53.23(d).
5. Zero drift, 12 and 24 hour.........  ppm.....................        minus>    minus>    minus>    minus>    minus>
                                                                     0.004     0.002      0.02       0.5       0.3      0.02
6. Span drift, 24 hour:
    20% of upper range limit..........  Percent.................  ........        minus>              minus>    minus>
                                                                                3.0      20.0                 2.0      20.0
    80% of upper range limit..........  Percent.................                  minus>    minus>              minus>
                                                                       3.0                 5.0       2.0                 5.0
7. Lag time...........................  Minutes.................         2         2        20       2.0       2.0        20  Sec. 53.23(e).
8. Rise time..........................  Minutes.................         2         2        15       2.0       2.0        15  Sec. 53.23(e).
9. Fall time..........................  Minutes.................         2         2        15       2.0       2.0        15  Sec. 53.23(e).
10. Precision:
    20% of upper range limit..........  ppm.....................  ........  ........     0.010  ........  ........     0.020  Sec. 53.23(e).
                                        Percent.................         2         2  ........       1.0       1.0  ........  Sec. 53.23(e).

    80% of upper range limit..........  ppm.....................  ........  ........     0.010  ........  ........     0.030  Sec. 53.23(e).
                                        Percent.................         2         2  ........       1.0       1.0  ........  Sec. 53.23(e).
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 To convert from parts per million (ppm) to [mu]g/m3 at 25 [deg]C and 760 mm Hg, multiply by M/0.02447, where M is the molecular weight of the gas.
  Percent means percent of the upper measurement range limit.
2 Tests for interference equivalent and lag time do not need to be repeated for any lower range provided the test for the standard range shows that the
  lower range specification (if applicable) is met for each of these test parameters.
3 For candidate analyzers having automatic or adaptive time constants or smoothing filters, describe their functional nature, and describe and conduct
  suitable tests to demonstrate their function aspects and verify that performances for calibration, noise, lag, rise, fall times, and precision are
  within specifications under all applicable conditions. For candidate analyzers with operator-selectable time constants or smoothing filters, conduct
  calibration, noise, lag, rise, fall times, and precision tests at the highest and lowest settings that are to be included in the FRM or FEM
  designation.
4 For nitric oxide interference for the SO2 UVF method, interference equivalent is  0.0003 ppm for the lower range.

Sec.  53.21  Test conditions.

    (a) Set-up and start-up of the test analyzer shall be in strict
accordance with the operating instructions specified in the manual
referred to in Sec.  53.4(b)(3). Allow adequate warm-up or
stabilization time as indicated in the operating instructions before
beginning the tests. The test procedures assume that the test analyzer
has a conventional analog measurement signal output that is connected
to a suitable strip chart recorder of the servo, null-balance type.
This recorder shall have a chart width of a least 25 centimeters, chart
speeds up to 10 cm per hour, a response time of 1 second or less, a
deadband of not more than 0.25 percent of full scale, and capability
either of reading measurements at least 5 percent below zero or of
offsetting the zero by at least 5 percent. If the test analyzer does
not have an analog signal output, or if a digital or other type of
measurement data output is used for the tests, an alternative
measurement data recording device (or devices) may be used for
recording the test data, provided that the device is reasonably suited
to the nature and purposes of the tests, and an analog representation
of the analyzer measurements for each test can be plotted or otherwise
generated that is reasonably similar to the analog measurement
recordings that would be produced by a conventional chart recorder
connected to a conventional analog signal output.
    (b) Calibration of the test analyzer shall be carried out prior to
conducting the tests described in this subpart. The calibration shall
be as indicated in the manual referred to in Sec.  53.4(b)(3) and as
follows: If the chart recorder or alternative data recorder does not
have below zero capability, adjust either the controls of the test
analyzer or the chart or data recorder to obtain a + 5% offset zero
reading on the recorder chart to facilitate observing negative response
or drift. If the candidate method is not capable of negative response,
the test analyzer (not the data recorder) shall be operated with a
similar offset zero. Construct and submit a calibration curve showing a
plot of recorder scale readings or other measurement output readings
(vertical or y-axis) against pollutant concentrations presented to the
analyzer for measurement (horizontal or x-axis). If applicable, a plot
of base analog output units (volts, millivolts, milliamps, etc.)
against pollutant concentrations shall also be obtained and submitted.
All such calibration plots shall consist of at least seven (7)
approximately equally spaced, identifiable points, including 0 and 90
 5 percent of the upper range limit (URL).
    (c) Once the test analyzer has been set up and calibrated and the
tests started, manual adjustment or normal periodic maintenance is
permitted only every 3 days. Automatic adjustments which the test
analyzer performs by itself are permitted at any time. The submitted
records shall show clearly when any manual adjustment or periodic
maintenance was made during the tests and describe the specific
operations performed.
    (d) If the test analyzer should malfunction during any of the
performance tests, the tests for that parameter shall be repeated. A
detailed explanation of the malfunction, remedial action taken, and
whether recalibration was necessary (along with all pertinent records
and charts) shall be submitted. If more than one malfunction occurs,
all performance test procedures for all parameters shall be repeated.
    (e) Tests for all performance parameters shall be completed on the
same test analyzer; however, use of multiple test analyzers to
accelerate testing is permissible for testing additional ranges of a
multi-range candidate method.

Sec.  53.22  Generation of test atmospheres.

    (a) Table B-2 specifies preferred methods for generating test
atmospheres and suggested methods of verifying their concentrations.
Only one means of establishing the concentration of a test atmosphere
is normally required, provided that that means is adequately accurate
and credible. If the method of generation can produce accurate,
reproducible concentrations, verification is optional. If the method of
generation is not reproducible or reasonably quantifiable, then
establishment of the concentration by some credible verification method
is required.
    (b) The test atmosphere delivery system shall be designed and
constructed so as not to significantly alter the test atmosphere
composition or concentration during the period of the test. The system
shall be vented to insure that test atmospheres are presented to the
test analyzer at very nearly atmospheric pressure. The delivery system
shall be fabricated from borosilicate glass, FEP Teflon, or other
material that is inert with regard to the gas or gases to be used.
    (c) The output of the test atmosphere generation system shall be
sufficiently stable to obtain stable response readings from the test
analyzer during the required tests. If a permeation device is used for
generation of a test atmosphere, the device, as well as the air passing
over it, shall be controlled to 0.1 [deg]C.
    (d) All diluent air shall be zero air free of contaminants likely
to react with the test atmospheres or cause a detectable response on
the test analyzer.
    (e) The concentration of each test atmosphere used shall be
quantitatively established and/or verified before or during each series
of tests. Samples for verifying test concentrations shall be

collected from the test atmosphere delivery system as close as feasible
to the sample intake port of the test analyzer.
    (f) The accuracy of all flow measurements used to calculate test
atmosphere concentrations shall be documented and referenced to a
primary flow rate or volume standard (such as a spirometer, bubble
meter, etc.). Any corrections shall be clearly shown. All flow
measurements given in volume units shall be standardized to 25 [deg]C.
and 760 mm Hg.
    (g) Schematic drawings, photos, descriptions, and other information
showing complete procedural details of the test atmosphere generation,
verification, and delivery system shall be provided. All pertinent
calculations shall be clearly indicated.

                                           Table B-2--Test Atmospheres
----------------------------------------------------------------------------------------------------------------
              Test gas                             Generation                           Verification
----------------------------------------------------------------------------------------------------------------
Ammonia............................  Permeation device. Similar to system   Indophenol method, reference 3.
                                      described in references 1 and 2.
Carbon dioxide.....................  Cylinder of zero air or nitrogen       Use NIST-certified standards
                                      containing CO2 as required to obtain   whenever possible. If NIST
                                      the concentration specified in table   standards are not available, obtain
                                      B-3.                                   2 standards from independent
                                                                             sources which agree within 2
                                                                             percent, or obtain one standard and
                                                                             submit it to an independent
                                                                             laboratory for analysis, which must
                                                                             agree within 2 percent of the
                                                                             supplier's nominal analysis.
Carbon monoxide....................  Cylinder of zero air or nitrogen       Use an FRM CO analyzer as described
                                      containing CO as required to obtain    in reference 8.
                                      the concentration specified in table
                                      B-3.
Ethane.............................  Cylinder of zero air or nitrogen       Gas chromatography, ASTM D2820,
                                      containing ethane as required to       reference 10. Use NIST-traceable
                                      obtain the concentration specified     gaseous methane or propane
                                      in table B-3.                          standards for calibration.
Ethylene...........................  Cylinder of pre-purified nitrogen      Do.
                                      containing ethylene as required to
                                      obtain the concentration specified
                                      in table B-3.
Hydrogen chloride..................  Cylinder \1\ of pre-purified nitrogen  Collect samples in bubbler
                                      containing approximately 100 ppm of    containing distilled water and
                                      gaseous HCl. Dilute with zero air to   analyze by the mercuric thiocyanate
                                      concentration specified in table B-3.  method, ASTM (D612), p. 29,
                                                                             reference 4.
Hydrogen sulfide...................  Permeation device system described in  Tentative method of analysis for H2S
                                      references 1 and 2.                    content of the atmosphere, p. 426,
                                                                             reference 5.
Methane............................  Cylinder of zero air containing        Gas chromatography ASTM D2820,
                                      methane as required to obtain the      reference 10. Use NIST-traceable
                                      concentration specified in table B-3.  methane standards for calibration.
Nitric oxide.......................  Cylinder \1\ of pre-purified nitrogen  Gas phase titration as described in
                                      containing approximately 100 ppm NO.   reference 6, section 7.1.
                                      Dilute with zero air to required
                                      concentration.
Nitrogen dioxide...................  1. Gas phase titration as described    1. Use an FRM NO2 analyzer
                                      in reference 6.                        calibrated with a gravimetrically
                                                                             calibrated permeation device.
                                     2. Permeation device, similar to       2. Use an FRM NO2 analyzer
                                      system described in reference 6.       calibrated by gas-phase titration
                                                                             as described in reference 6.
Ozone..............................  Calibrated ozone generator as          Use an FEM ozone analyzer calibrated
                                      described in reference 9.              as described in reference 9.
Sulfur dioxide.....................  1. Permeation device as described in   Use an SO2 FRM or FEM analyzer as
                                      references 1 and 2.                    described in reference 7.
                                     2. Dynamic dilution of a cylinder      ....................................
                                      containing approximately 100 ppm SO2
                                      as described in Reference 7.
Water..............................  Pass zero air through distilled water  Measure relative humidity by means
                                      at a fixed known temperature between   of a dew-point indicator,
                                      20[deg] and 30[deg] C such that the    calibrated electrolytic or piezo
                                      air stream becomes saturated. Dilute   electric hygrometer, or wet/dry
                                      with zero air to concentration         bulb thermometer.
                                      specified in table B-3.
Xylene.............................  Cylinder of pre-purified nitrogen      Use NIST-certified standards
                                      containing 100 ppm xylene. Dilute      whenever possible. If NIST
                                      with zero air to concentration         standards are not available, obtain
                                      specified in table B-3.                2 standards from independent
                                                                             sources which agree within 2
                                                                             percent, or obtain one standard and
                                                                             submit it to an independent
                                                                             laboratory for analysis, which must
                                                                             agree within 2 percent of the
                                                                             supplier's nominal analysis.
Zero air...........................  1. Ambient air purified by             ....................................
                                      appropriate scrubbers or other
                                      devices such that it is free of
                                      contaminants likely to cause a
                                      detectable response on the analyzer.
                                     2. Cylinder of compressed zero air     ....................................
                                      certified by the supplier or an
                                      independent laboratory to be free of
                                      contaminants likely to cause a
                                      detectable response on the analyzer.
----------------------------------------------------------------------------------------------------------------
\1\ Use stainless steel pressure regulator dedicated to the pollutant measured.
Reference 1. O'Keefe, A. E., and Ortaman, G. C. ``Primary Standards for Trace Gas Analysis,'' Anal. Chem. 38,
  760 (1966).
Reference 2. Scaringelli, F. P., A. E. Rosenberg, E*, and Bell, J. P., ``Primary Standards for Trace Gas
  Analysis.'' Anal. Chem. 42, 871 (1970).
Reference 3. ``Tentative Method of Analysis for Ammonia in the Atmosphere (Indophenol Method)'', Health Lab
  Sciences, vol. 10, No. 2, 115-118, April 1973.
Reference 4. 1973 Annual Book of ASTM Standards, American Society for Testing and Materials, 1916 Race St.,
  Philadelphia, PA.
Reference 5. Methods for Air Sampling and Analysis, Intersociety Committee, 1972, American Public Health
  Association, 1015.
Reference 6. 40 CFR 50 Appendix F, ``Measurement Principle and Calibration Principle for the Measurement of
  Nitrogen Dioxide in the Atmosphere (Gas Phase Chemiluminescence).''
Reference 7. 40 CFR 50 Appendix A-1, ``Measurement Principle and Calibration Procedure for the Measurement of
  Sulfur Dioxide in the Atmosphere (Ultraviolet Fluorscence).''
Reference 8. 40 CFR 50 Appendix C, ``Measurement Principle and Calibration Procedure for the Measurement of
  Carbon Monoxide in the Atmosphere'' (Non-Dispersive Infrared Photometry)''.

Reference 9. 40 CFR 50 Appendix D, ``Measurement Principle and Calibration Procedure for the Measurement of
  Ozone in the Atmosphere''.
Reference 10. ``Standard Test Method for C, through C5 Hydrocarbons in the Atmosphere by Gas Chromatography'', D
  2820, 1987 Annual Book of Aston Standards, vol 11.03, American Society for Testing and Materials, 1916 Race
  St., Philadelphia, PA 19103.

Sec.  53.23  Test procedures.

    (a) Range--(1) Technical definition. The nominal minimum and
maximum concentrations that a method is capable of measuring.

    Note to Sec.  53.23(a)(1): The nominal range is given as the
lower and upper range limits in concentration units, for example, 0-
0.5 parts per million (ppm).

    (2) Test procedure. Determine and submit a suitable calibration
curve, as specified in Sec.  53.21(b), showing the test analyzer's
measurement response over at least 95 percent of the required or
indicated measurement range.

    Note to Sec.  53.23(a)(2):  A single calibration curve for each
measurement range for which an FRM or FEM designation is sought will
normally suffice.

    (b) Noise--(1) Technical definition. Spontaneous, short duration
deviations in measurements or measurement signal output, about the mean
output, that are not caused by input concentration changes. Measurement
noise is determined as the standard deviation of a series of
measurements of a constant concentration about the mean and is
expressed in concentration units.
    (2) Test procedure. (i) Allow sufficient time for the test analyzer
to warm up and stabilize. Determine measurement noise at each of two
fixed concentrations, first using zero air and then a pollutant test
gas concentration as indicated below. The noise limit specification in
table B-1 shall apply to both of these tests.
    (ii) For an analyzer with an analog signal output, connect an
integrating-type digital meter (DM) suitable for the test analyzer's
output and accurate to three significant digits, to determine the
analyzer's measurement output signal.

    Note to Sec.  53.23(b)(2):  Use of a chart recorder in addition
to the DM is optional.

    (iii) Measure zero air with the test analyzer for 60 minutes.
During this 60-minute interval, record twenty-five (25) test analyzer
concentration measurements or DM readings at 2-minute intervals. (See
Figure B-2 in appendix A of this subpart.)
    (iv) If applicable, convert each DM test reading to concentration
units (ppm) or adjust the test readings (if necessary) by reference to
the test analyzer's calibration curve as determined in Sec.  53.21(b).
Label and record the test measurements or converted DM readings as
r1, r2, r3 * * * ri * * *
r25.
    (v) Calculate measurement noise as the standard deviation, S, as
follows:
[GRAPHIC] [TIFF OMITTED] TP11FE11.140

where i indicates the i-th test measurement or DM reading in ppm.

    (vi) Let S at 0 ppm be identified as S0; compare
S0 to the noise limit specification given in table B-1.
    (vii) Repeat steps in Paragraphs (b)(2)(iii) through (v) of this
section using a pollutant test atmosphere concentration of 80  5 percent of the URL instead of zero air, and let S at 80
percent of the URL be identified as S80. Compare
S80 to the noise limit specification given in table B-1 of
this subpart.
    (viii) Both S0 and S80 must be less than or
equal to the table B-1 noise limit specification to pass the test for
the noise parameter.
    (c) Lower detectable limit--(1) Technical definition. The minimum
pollutant concentration that produces a measurement or measurement
output signal of at least twice the noise level.
    (2) Test procedure. (i) Allow sufficient time for the test analyzer
to warm up and stabilize. Measure zero air and record the stable
measurement reading in ppm as BZ. (See Figure B-3 in
appendix A of this subpart.)
    (ii) Generate and measure a pollutant test concentration equal to
the value for the lower detectable limit specified in table B-1.

    Note to Sec.  53.23(c)(2):  If necessary, the test concentration
may be generated or verified at a higher concentration, then
quantitatively and accurately diluted with zero air to the final
required test concentration.

    (iii) Record the test analyzer's stable measurement reading, in
ppm, as BL.
    (iv) Determine the lower detectable limit (LDL) test result as LDL
= BL - BZ. Compare this LDL value with the noise
level, S0, determined in Sec.  53.23(b), for the 0
concentration test atmosphere. LDL must be equal to or higher than 2 x
S0 to pass this test.
    (d) Interference equivalent--(1) Technical definition. Positive or
negative measurement response caused by a substance other than the one
being measured.
    (2) Test procedure. The test analyzer shall be tested for all
substances likely to cause a detectable response. The test analyzer
shall be challenged, in turn, with each potential interfering agent
(interferent) specified in table B-3. In the event that there are
substances likely to cause a significant interference which have not
been specified in table B-3, these substances shall also be tested, in
a manner similar to that for the specified interferents, at a
concentration substantially higher than that likely to be found in the
ambient air. The interference may be either positive or negative,
depending on whether the test analyzer's measurement response is
increased or decreased by the presence of the interferent. Interference
equivalents shall be determined by mixing each interferent, one at a
time, with the pollutant at an interferent test concentration not lower
than the test concentration specified in table B-3 (or as otherwise
required for unlisted interferents), and comparing the test analyzer's
measurement response to the response caused by the pollutant alone.
Known gas-phase reactions that might occur between a listed interferent
and the pollutant are designated by footnote 3 in table B-3. In these
cases, the interference equivalent shall be determined without mixing
with the pollutant.
    (i) Allow sufficient time for warm-up and stabilization of the test
analyzer.
    (ii) For a candidate method using a prefilter or scrubber device
based upon a chemical reaction to derive part of its specificity and
which device requires periodic service or maintenance, the test
analyzer shall be ``conditioned'' prior to conducting each interference
test series. This requirement includes conditioning for the
NO2 converter in chemiluminescence NO/NO2/
NOX analyzers and for the ozone scrubber in UV-absorption
ozone analyzers. Conditioning is as follows:
    (A) Service or perform the indicated maintenance on the scrubber or
prefilter device, as if it were due for such maintenance, as directed
in the manual referred to in Sec.  53.4(b)(3).
    (B) Before testing for each potential interferent, allow the test
analyzer to sample through the prefilter or scrubber device a test
atmosphere containing the interferent at a concentration not lower than
the value specified in table B-3 (or, for unlisted potential
interferents, at a concentration substantially higher than likely to be
found in ambient air). Sampling shall be at the normal flow rate and
shall be continued for 6 continuous hours prior to the interference
test series. Conditioning for all applicable interferents prior to any
of

the interference tests is permissible. Also permissible is simultaneous
conditioning with multiple interferents, provided no interferent
reactions are likely to occur in the conditioning system.
    (iii) Generate three test atmosphere streams as follows:
    (A) Test atmosphere P: Pollutant test concentration.
    (B) Test atmosphere I: Interferent test concentration.
    (C) Test atmosphere Z: Zero air.
    (iv) Adjust the individual flow rates and the pollutant or
interferent generators for the three test atmospheres as follows:
    (A) The flow rates of test atmospheres I and Z shall be equal.
    (B) The concentration of the pollutant in test atmosphere P shall
be adjusted such that when P is mixed (diluted) with either test
atmosphere I or Z, the resulting concentration of pollutant shall be as
specified in table B-3.
    (C) The concentration of the interferent in test atmosphere I shall
be adjusted such that when I is mixed (diluted) with test atmosphere P,
the resulting concentration of interferent shall be not less than the
value specified in table B-3 (or as otherwise required for unlisted
potential interferents).
    (D) To minimize concentration errors due to flow rate differences
between I and Z, it is recommended that, when possible, the flow rate
of P be from 10 to 20 times larger than the flow rates of I and Z.
    (v) Mix test atmospheres P and Z by passing the total flow of both
atmospheres through a (passive) mixing component to insure complete
mixing of the gases.
    (vi) Sample and measure the mixture of test atmospheres P and Z
with the test analyzer. Allow for a stable measurement reading, and
record the reading, in concentration units, as R (see Figure B-3).
    (vii) Mix test atmospheres P and I by passing the total flow of
both atmospheres through a (passive) mixing component to insure
complete mixing of the gases.
    (viii) Sample and measure this mixture of P and I with the test
analyzer. Record the stable measurement reading, in concentration
units, as RI.
    (ix) Calculate the interference equivalent (IE) test result as:

    IE = RI - R.

IE must be within the limits (inclusive) specified in table B-1 for
each interferent tested to pass the interference equivalent test.

    (x) Follow steps (iii) through (ix) of this section, in turn, to
determine the interference equivalent for each listed interferent as
well as for any other potential interferents identified.
    (xi) For those potential interferents which cannot be mixed with
the pollutant, as indicated by footnote (3) in table B-3, adjust the
concentration of test atmosphere I to the specified value without being
mixed or diluted by the pollutant test atmosphere. Determine IE as
follows:
    (A) Sample and measure test atmosphere Z (zero air). Allow for a
stable measurement reading and record the reading, in concentration
units, as R.
    (B) Sample and measure the interferent test atmosphere I. If the
test analyzer is not capable of negative readings, adjust the analyzer
(not the recorder) to give an offset zero. Record the stable reading in
concentration units as RI, extrapolating the calibration
curve, if necessary, to represent negative readings.
    (C) Calculate IE = RI - R. IE must be within the limits
(inclusive) specified in table B-1 for each interferent tested to pass
the interference equivalent test.
    (xii) Sum the absolute value of all the individual interference
equivalent test results. This sum must be equal to or less than the
total interferent limit given in table B-1 to pass the test.
BILLING CODE 6560-50-P

[GRAPHIC] [TIFF OMITTED] TP11FE11.141

[GRAPHIC] [TIFF OMITTED] TP11FE11.142

BILLING CODE 6560-50-C
    (e) Zero drift, span drift, lag time, rise time, fall time, and
precision--(1) Technical definitions--(i) Zero drift. The change in
measurement response to

zero pollutant concentration over 12- and 24-hour periods of continuous
unadjusted operation.
    (ii) Span drift. The percent change in measurement response to an
up-scale pollutant concentration over a 24-hour period of continuous
unadjusted operation.
    (iii) Lag time. The time interval between a step change in input
concentration and the first observable corresponding change in
measurement response.
    (iv) Rise time. The time interval between initial measurement
response and 95 percent of final response after a step increase in
input concentration.
    (v) Fall time. The time interval between initial measurement
response and 95 percent of final response after a step decrease in
input concentration.
    (vi) Precision. Variation about the mean of repeated measurements
of the same pollutant concentration, expressed as one standard
deviation.
    (2) Tests for these performance parameters shall be accomplished
over a period of seven (7) or fifteen (15) test days. During this time,
the line voltage supplied to the test analyzer and the ambient
temperature surrounding the analyzer shall be changed from day to day,
as required in paragraph(e)(4) of this section. One test result for
each performance parameter shall be obtained each test day, for seven
(7) or fifteen (15) test days, as determined from the test results of
the first seven days. The tests for each test day are performed in a
single integrated procedure.
    (3) The 24-hour test day may begin at any clock hour. The first
approximately 12 hours of each test day are required for testing 12-
hour zero drift. Tests for the other parameters shall be conducted any
time during the remaining 12 hours.
    (4) Table B-4 of this section specifies the line voltage and room
temperature to be used for each test day. The applicant may elect to
specify a wider temperature range (minimum and maximum temperatures)
than the range specified in table B-4 and to conduct these tests over
that wider temperature range in lieu of the specified temperature
range. If the test results show that all test parameters of this
section Sec.  53.23(e) are passed over this wider temperature range, a
subsequent FRM or FEM designation for the candidate method based in
part on this test shall indicate approval for operation of the method
over such wider temperature range. The line voltage and temperature
shall be changed to the specified values (or to the alternative, wider
temperature values, if applicable) at the start of each test day (i.e.,
at the start of the 12-hour zero test). Initial adjustments (day zero)
shall be made at a line voltage of 115 volts (rms) and a room
temperature of 25 [deg]C.
    (5) The tests shall be conducted in blocks consisting of 3 test
days each until 7 (or 15, if necessary) test results have been
obtained. (The final block may contain fewer than three test days.)
Test days need not be contiguous days, but during any idle time between
tests or test days, the test analyzer must operate continuously and
measurements must be recorded continuously at a low chart speed (or
equivalent data recording) and included with the test data. If a test
is interrupted by an occurrence other than a malfunction of the test
analyzer, only the block during which the interruption occurred shall
be repeated.
    (6) During each test block, manual adjustments to the electronics,
gas, or reagent flows or periodic maintenance shall not be permitted.
Automatic adjustments that the test analyzer performs by itself are
permitted at any time.
    (7) At least 4 hours prior to the start of the first test day of
each test block, the test analyzer may be adjusted and/or serviced
according to the periodic maintenance procedures specified in the
manual referred to in Sec.  53.4(b)(3). If a new block is to
immediately follow a previous block, such adjustments or servicing may
be done immediately after completion of the day's tests for the last
day of the previous block and at the voltage and temperature specified
for that day, but only on test days 3, 6, 9, and 12.

    Note to Sec.  53.23(e)(7): If necessary, the beginning of the
test days succeeding such maintenance or adjustment may be delayed
as required to complete the service or adjustment operation.

    (8) All measurement response readings to be recorded shall be
converted to concentration units or adjusted (if necessary) according
to the calibration curve. Whenever a test atmosphere is to be measured
but a stable reading is not required, the test atmosphere shall be
sampled and measured long enough to cause a change in measurement
response of at least 10% of full scale. Identify all readings and other
pertinent data on the strip chart (or equivalent test data record).
(See Figure B-1 illustrating the pattern of the required readings.)

                                              Table B-4--Line Voltage and Room Temperature Test Conditions
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                       Line           Room
             Test day              voltage,\1\  temperature,\2\                                          Comments
                                       rms           [deg]C
--------------------------------------------------------------------------------------------------------------------------------------------------------
0................................          115             25    Initial set-up and adjustments.
1................................          125             20    .......................................................................................
2................................          105             20    .......................................................................................
3................................          125             30    Adjustments and/or periodic maintenance permitted at end of tests.
4................................          105             30    .......................................................................................
5................................          125             20    .......................................................................................
6................................          105             20    Adjustments and/or periodic maintenance permitted at end of tests.
7................................          125             30    Examine test results to ascertain if further testing is required.
8................................          105             30    .......................................................................................
9................................          125             20    Adjustments and/or periodic maintenance permitted at end of tests.
10...............................          105             20    .......................................................................................
11...............................          125             30    .......................................................................................
12...............................          105             30    Adjustments and/or periodic maintenance permitted at end of tests.
13...............................          125             20    .......................................................................................
14...............................          105             20    .......................................................................................
15...............................          125             30    .......................................................................................
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Voltage specified shall be controlled to  1 volt.
\2\ Temperatures shall be controlled to 1 [deg]C.

BILLING CODE 6560-60-P
[GRAPHIC] [TIFF OMITTED] TP11FE11.143

BILLING CODE 6560-60-C
    (9) Test procedure. (i) Arrange to generate pollutant test
atmospheres as follows. Test atmospheres A0, A20,
and A80 shall be maintained consistent during the tests and
reproducible from test day to test day.

------------------------------------------------------------------------
         Test  atmosphere             Pollutant concentration (percent)
------------------------------------------------------------------------
A0................................  Zero air.
A20...............................  205 of the upper range
                                     limit.
A30...............................  305 of the upper range
                                     limit.
A80...............................  805 of the upper range
                                     limit.
A90...............................  905 of the upper range
                                     limit.
------------------------------------------------------------------------

     (ii) For steps within paragraphs (e)(9)(xxv) through (e)(9)(xxxi)
of this section, a chart speed of at least 10 centimeters per hour (or
equivalent resolution for a digital representation) shall be used to
clearly show changes in measurement responses. The actual chart speed,
chart speed changes, and time checks shall be clearly marked on the
chart.
    (iii) Test day 0. Allow sufficient time for the test analyzer to
warm up and stabilize at a line voltage of 115 volts and a room
temperature of 25 [deg]C. Adjust the zero baseline to 5 percent of
chart (see Sec.  53.21(b)) and recalibrate, if necessary. No further
adjustments shall be made to the analyzer until the end of the tests on
the third, sixth, ninth, or twelfth test day.
    (iv) Measure test atmosphere A0 until a stable
measurement reading is obtained and record this reading (in

ppm) as Z'n, where n = 0 (see Figure B-4 in appendix A of this
subpart).
    (v) [Reserved]