Of the two decay studies by Matthews et al., the “slow” study is believed to be more indicative of the formaldehyde decay behavior in residences. However, the authors added the caution that care should be taken in interpreting the study results. For example, the duration of the study may have been inadequate to accurately reflect the emission decay period for the collection of sources. In addition, the data may reflect a relatively rapid decay of emissions from a few of the strongest emitting sources, as opposed to the entire collection of products, whereas in real life one might typically expect to find a combination of relatively strong and weak emitters, or of sources and sinks.

In another decay study for an individual source, Zinn et al. estimated an apparent half-life of 216 days (0.6 years) using approximately one year of large chamber data for particleboard and a natural logarithm linear regression statistical analysis. As noted by one of the peer reviewers:

The half-life reported in Zinn et al. (1990) is not directly comparable to that adopted in the original and current Versar model because Zinn et al. used the relationship HCHO = F + G x ln(time) with regression constants F and G whereas the EPA half-life was based on a traditional exponential decay model. The Zinn et al. logarithmic equation was used by CARB to calculate the emissions inventory presented in the technical basis for the formaldehyde airborne toxic control measure. In lieu of the original logarithmic equation, the more generic two-compartment (i.e., fast and slow decay) exponential decay model could be fit the Zinn et al. data.

For the various reasons noted in the above review and discussion, there is considerable uncertainty as to the most appropriate value to represent the central tendency for the decay rate of formaldehyde, in a residence where construction features, house contents and occupant activities remain relatively stable over time. The cross-sectional data from residential studies are believed to yield estimates erring on the high side (i.e., longer estimated than actual half-life), and the temporal data from chamber studies are believed to yield estimates erring in the opposite direction.

The collective evidence described above indicates that an appropriate half-life value probably lies between 1.5 and 3.0 years. The value of 2.92 years from the cross-sectional analysis described above will tend to err on the conservative side. That is, assuming that the initial concentration in a house is predicted accurately, the 2.92-year value likely will cause the modeled concentration to decay at a slower rate than might be observed in a stable residential setting.

A 2005 paper by Groah focused on the topic of decay in formaldehyde concentrations over time. The author notes that “newer sources of formaldehyde are continually being brought into homes as they age.” Examples would include the installation of new kitchen cabinets when remodeling or the addition of new furnishings such as furniture or shelving that may contain pressed-wood products. To the extent that such situations exert an upward bias on half-life estimates that are based on an analysis of homes of different ages, it could be argued that the default half-life value of 2.92 years is too conservative, as mentioned above. Two studies were noted by Groah that involved chamber testing of a collection of pressed-wood products as they aged. One (by Matthews et al., cited on the previous page) estimated the emissions half-life to be 1.52 years and the other (Groah and Gramp) indicated a half-life of 2.10 years. Based on these studies, a half-life on the order of 1.5 to 2.0 years is suggested should the user wish to apply a less conservative value.

3.9	Temperature and Humidity Adjustments

As noted in Section 2 and in the introduction to this section, the model initially estimates the formaldehyde concentration(s) in a structure under indoor conditions of 23 ( C temperature and 50 % relative humidity – these are consistent with the conditions under which most chamber tests have been conducted, in accordance with ASTM standard E 1333, for estimation of emission rates or concentrations under an assumed steady-state condition. The model then adjusts the initial concentration estimates under “standard conditions” to the user’s inputs for temperature and humidity.

The temperature adjustment used in the model is of the form:

 	(Eqn. 3-31)

where:

CT	=	Temperature-adjusted formaldehyde concentration

C0	=	Formaldehyde concentration at the baseline temperature

R	=	Temperature coefficient for adjustment

TU	=	User-specified temperature, ( K

TB	=	Baseline temperature, 296 ( K (23 ( C).

The humidity adjustment, applied to the temperature-adjusted concentration, is of the form:

   	(Eqn. 3-32)

where:

CTH	=	Temperature- and humidity-adjusted formaldehyde concentration

CT	=	Temperature-adjusted formaldehyde concentration

A	=	Humidity coefficient for adjustment

HU	=	User-specified relative humidity, %

HB	=	Baseline relative humidity, 50 %.

Combining equations 3-31 and 3-32, the temperature- and humidity-adjusted concentration can be expressed as follows:

 	(Eqn. 3-33)

where KTH is the combined temperature and humidity adjustment factor:

 	(Eqn. 3-34)

Thus, the adjustments require temperature and humidity coefficients, for which the model provides two alternative sets of values. The first set of coefficients – the model default -- was calculated by Berge et al. for two Norwegian particleboard specimens. These coefficients were used by HUD in setting the 1984 standards for particleboard and hardwood plywood paneling, and also have been used in ASTM, ANSI and Composite Panel Association (CPA) standards or guidelines. Chamber tests underlying these coefficients were conducted at two temperatures (22 and 28 (C) and at two relative humidities (30 and 60 %). The coefficients reported by Berge et al. were 9799 for temperature (assumes an Arrhenius type of model) and 0.0175 for humidity (assumes a linear model).

The second set of coefficients was reported by Myers, who reviewed the extant literature and developed his recommended temperature coefficient based on chamber testing of about 40 specimens (particleboard and hardwood plywood paneling) from 11 laboratories. The temperature range of the product tests was from 20 to 40 (C. Dr. Myers also developed a humidity coefficient, but expressed little confidence in the number; the relative humidities in the tests on which the correction factor was based ranged from 20 to 90 percent. Thus, his work encompassed more products and wider temperature/humidity ranges than the Berge et al. study. It is worth noting that the HUD standard was promulgated before Dr. Myers completed his work. His reported correction coefficients were 8930 for temperature and 0.0195 for relative humidity, using the same model assumptions as Berge et al.

The temperature and humidity adjustments modify the emission rate from pressed-wood products and, therefore, the portion of the indoor concentration due to indoor sources and sinks. That is, the temperature and humidity adjustment is applied only to the portion of the steady-state concentration contributed by pressed-wood products. The adjustment applied to the two-zone concentrations calculated using Equations 3-12 and 3-13 takes the following form:

 	(Eqn. 3-35)

 	(Eqn. 3-36)

Similarly, the adjustment applied to the one-zone concentration calculated using Equation 3-8 takes the following form:

 	(Eqn. 3-37)

3.10	Exposure Calculations

As noted in Section 2.5, the model calculates the following exposure metrics for each zone of the house or other modeled structure:

Average daily concentration (ADC)

Percent of time concentration is greater than the user-specified level of interest (LOI).

The ADC in each zone is calculated in yearly increments, by integrating Equation 3-21. The value of this integral, between two times (t1 and t2) that are exactly one year apart, is as follows:

 ADC = ((Ci  - CB)/-k)*e-k*t2 + CB*t2 - ((Ci  - CB)/-k)*e-k*t1 - CB*t1  (Eqn. 3-38)

  where:

Ci	=	initial concentration indoors (ppb)

CB	=	background concentration indoors (ppb)

k	=	first-order rate constant for the exponential decline (years-1)

t1	=	starting time (years)

t2	=	ending time (years).

For a new house, the values of t1 and t2 for the first year are 0 years and 1 year, respectively. The t1 and t2 values are 1 and 2 years for the second year, 2 and 3 years for the third year, and so on. If, for example, the starting concentration (i.e., at t1 = 0 years) were 57.5 ppb, the background concentration were 7.5 ppb, and the value of k were 0.462 years-1 (half life of 1.5 years), then the ending concentration would be 39 ppb per Equation 3-21 and the value of the integral for the first year would be 47.5 ppb per Equation 3-38.

The percent of time during which the concentration in a modeled zone is greater than the LOI also is calculated in yearly increments, as follows:

% Time =100 * (ln(Ci-CB) - ln(LOI-CB)) / k – t2)	(Eqn. 3-39)

where:

% Time 	=	percent of time concentration is greater than LOI

LOI 	=	level of interest (ppb).

Continuing with the example where Ci = 57.5 ppb, CB = 7.5 ppb, and t1 = 0 (i.e., new house), and with a value of 10 ppb for the LOI, the calculation result for each of the first six years (i.e., for t2 ranging from 1 to 6) is equal to 100%. For year 7 (t2 = 7) the calculation result is 48.4%; thereafter, the calculation result is negative, which the model resets to a value of 0%.

The ADC for any exposure group is calculated, in yearly increments, as a weighted average of concentrations encountered in each zone of the house or other modeled structure and concentrations encountered in non-home locations:

ADC = (HZ1*ADCZ1 + HZ2*ADCZ2 + HWSD*CWSD + HV*CV+ HO*CO) / 8760 	(Eqn. 3-40)

where:

H		=	hours spent per location

ADC	=	average daily concentration in Zone 1 or Zone 2 (ppb)

Z1				refers to Zone 1

Z2				refers to Zone 2

C		=	concentration at location away from home (ppb)

WSD 			refers to work, school or daycare location

V	 			refers to in-vehicle location

O				refers to other/outdoor location

The ADC values per zone decrease with each passing year, per Equation 3-38, whereas concentrations in locations outside or away from the home or modeled structure are assumed to be constant across the years. The sum of hours across the various locations (Z1, Z2, WSD, V and O) must equal 8760 for the calculation result to be valid. For a one-zone modeled structure, Z2 is set equal to Z1 for the calculation.

4.	 EVALUATION OF MODEL ALGORITHMS AND PREDICTIONS

The evaluation of the model has been performed from two perspectives: (1) independent checks on the correctness of model algorithms; and (2) comparison of model predictions with measurements in real-world situations.

4.1	Mathematical Correctness of Model Algorithms

An Excel spreadsheet has been developed as a tool for assessing the mathematical correctness of algorithms used in the model. The Excel tool includes individual sheets for inputs corresponding to model input screens – House, Source, and Exposure – together with a separate sheet that displays the calculation results (predicted HCHO concentrations). Input areas within each screen are set up similarly to those in the model, with the exception that no drop-down selections are provided for sources, sinks or cabinets. Instead, input areas (cells) are designated for direct entry of Slope, B and Area values. Results are provided for both the one-zone and two-zone implementation of the model, in concentration units of mg/m3 and ppm.

Results in the Excel tool were compared with those reported by the model for a variety of cases representing different combinations/values for background concentrations, sources, and exposure groups, for both one-zone and two-zone implementations. This exercise led to discovery of minor errors in an earlier version in the handling of ppm vs. mg/m3 units for the background concentration (now ppb and µg/m3 units) and in the temperature/humidity adjustment for indoor formaldehyde concentrations. Other than those discrepancies, the results agreed exactly in all cases. The errors discovered in the model’s calculation routine have been corrected.

4.2	NIST Assessment of Matthews Model Predictions

An effort was undertaken by researchers at the National Institute of Standards and Technology (NIST) to validate the Matthews model on which this model is based. Particleboard underlayment, hardwood-plywood paneling and medium-density fiberboard (MDF) products initially were characterized in chambers by measuring their HCHO surface emission rates over a range of formaldehyde concentrations, air exchange rates and two combinations of temperature and relative humidity. The products then were installed in a two-room prototype house in different combinations, and equilibrium HCHO concentrations were monitored in the house.

The following findings are excerpted directly from the authors’ abstract:

Particleboard underlayment and mdf, but not paneling, behaved as the emission model predicted over a large concentration range, under both sets of temperature and relative humidity. Good agreement was also obtained between measured formaldehyde concentrations and those predicted by a mass-balance indoor air quality model.

The mass-balance model referenced here is the Matthews model. The following excerpt, taken directly from the authors’ conclusions, provides some further insights on model performance:

In developing its models, ORNL assumed that there is relatively free formaldehyde diffusion within the "bulk phase" of pressed-wood products. Formaldehyde emission results from the difference in concentration between this "bulk phase" and the atmosphere, in accordance with Fick's first diffusion law. This assumption is apparently fairly descriptive of particleboard and mdf, but not of hardwood plywood paneling. It is hypothesized that internal diffusion is important in formaldehyde emission by pressed-wood products, and layering of solid thin sheets of plywood obstructs diffusion to a greater extent than do chips and pieces in the other pressed-wood products. In other words, formaldehyde emission may not be as diffusion-limited in plywood as it is in other pressed-wood products. This would explain why formaldehyde emission by plywood appeared relatively insensitive to temperature and RH used in the present study. Higher temperature and RH increase resin degradation to formaldehyde and increase the formaldehyde diffusion rate. Apparently, the small changes of temperature and RH used in the present study did not increase the "bulk phase" formaldehyde concentration or the diffusion rate sufficiently to overcome the obstructing layers of the relatively low-emitting plywood used in this study.

It is noteworthy here that particleboard and MDF generally are much higher HCHO emitters than plywood or hardwood plywood paneling. Thus, the NIST validation effort indicated accurate model predictions for the major HCHO emitters among pressed-wood products.

4.3	Assessment of FIAM-pwp Predictions – EPA Pilot Study

An assessment undertaken by the author of this document involved comparison of model predictions with concentrations measured in the EPA pilot study house under various conditions, including before and after loading the house with pressed-wood products. The assessment was conducted by using known/measured factors such as zone volumes, airflow rates, indoor temperature and humidity, and source/sink loading areas together with estimates of emission model parameters for each type of source or sink. Model inputs were developed for six cases (time periods within the pilot study) at the conventional house – initial baseline, first loading, air-out after first loading, second loading, air-out after second loading, and third loading. Inputs supplied for model input screens – House, Sources and Sinks – are described in a general manner below. Further details specific to each of the six cases are given in the subsections that follow.

The house screen requires inputs for the type of house, the zone volumes and airflow rates, the background formaldehyde concentration, and the indoor temperature and humidity conditions. The house used for the pilot study – Conventional 1 – was selected. Airflow measurements with PFTs on 14 different occasions during the pilot study averaged 0.59 ACH and varied over a relatively narrow range of 0.5 to 0.7 ACH. The default airflow rates provided with the model for this conventional house, which correspond to an air exchange rate of 0.59 ACH, were used for all model runs.

Outdoor formaldehyde concentration measurements during the pilot study varied over the narrow range of 0.001 to 0.003 ppm, averaging about 0.002 ppm. The average of 0.002 ppm was used for this input rather than case-specific values. The model calculates formaldehyde levels in each zone of the house under a base set of temperature/humidity conditions (23 (C, 50 %) and a user-supplied set of conditions. The user-supplied conditions were chosen to represent the average of the values measured upstairs for each case at the conventional house. The major formaldehyde sources all were located upstairs. The default temperature and humidity coefficients provided with the model, for adjustment of modeled formaldehyde concentrations from the base conditions to the user-supplied conditions, were used for all model runs.

Model parameters for sources – Slope and B – have been estimated previously from large-chamber emission tests conducted by industry or the USEPA, and are supplied with the model. The major sources installed in the conventional house – underlayment, kitchen/bathroom cabinets, interior doors, and hardwood plywood – were chamber tested under three different air exchange rates as part of the pilot study. Source loading areas for the model runs are described later as they pertain to each modeled case.

There are two major types of potential sinks in conventional house 1 – carpet/padding and painted wallboard. Sinks can be represented in the Matthews model using the same parameters as those for sources. The Langmuir isotherm model described in the formaldehyde pilot study report (p. 6-44) was used to develop parameter estimates for sinks, for use in the Matthews model.

The modeling approach, rationale and assumptions for each of the six modeled cases are described below. The results of this evaluation exercise collectively indicate that the modified (two-zone) Matthews model can predict measured values quite well for the conventional house, but errs somewhat on the conservative side (i.e., it tends to “over-predict”). The greatest area of uncertainty in applying the model appears to be in choosing appropriate values for indoor sinks. One additional area of uncertainty stems from the fact that humidity levels were not measured downstairs; as noted previously, upstairs values for temperature and humidity were used in constructing the model inputs.

4.3.1	Initial Baseline Period

Model inputs for this period are summarized in Table 4-1. The only source present in the house during the initial baseline period was the plywood subfloor, and the only sink was painted wallboard (carpet was not yet installed). The area for plywood was taken as the product of the upstairs volume (304 m3) and an assumed loading ratio of 0.43 m2/m3, or 131 m2. For wallboard the loading ratios for walls (0.95 m2/m3) and ceilings (0.43 m2/m3) were used to estimate a total area of 420 m2. Model source/sink parameters (intercept and slope) were taken from the model defaults for softwood plywood. An intercept value of 0.04 mg/m2-h was chosen for wallboard after running the model with plywood only and obtaining an indoor formaldehyde concentration in the vicinity of 10 ppb.

Table 4-1.  Model Inputs (Sources and Sinks) for Initial Baseline Period

Source/Sink

Slope (m/h)

Intercept (mg/m2-h)

Area (m2)

Softwood plywood

-0.61

0.03

131

Painted wallboard

-3.00

0.04

420

Modeling results for the initial baseline are shown in Table 4-2. With plywood as the only source, and without including wallboard as a sink, the modeled values for the conditions under which measurements were taken (23.98 ( C, 23.6 % RH) were 8 ppb upstairs and 7 ppb downstairs, close to the measured values of 9.5 and 9.1 ppb for the respective zones. Addition of wallboard as a sink had no appreciable effect on the modeled values. It is plausible that, at this point in time, the wallboard had reached a state of equilibrium and, thus, acted as neither a net source nor a net sink. When the intercept parameter for wallboard was arbitrarily halved (to 0.02 mg/m2-h), to cause it to behave as net sink, the modeled values were 5.0 ppb upstairs and 4.4 ppb downstairs under the conditions when measurements were taken.

Table 4-2.  Modeling Results for Initial Baseline Period

Source/Sink Inputs

Results (ppb) for Base/Measured Conditions

23 ( C, 50 % RH

23.98 ( C, 23.6 % RH

Upstairs

Downstairs

Upstairs

Downstairs

Softwood plywood as a source

10.3

9.0

7.8

6.9

Add wallboard as a sink

10.7

9.4

8.2

7.2

Measured values

--

--

  9.5*

9.1

*The measured value is an average across 3 monitoring sites (living room, kitchen and bedroom).

4.3.2	First Loading

The modeled sources for the first (medium) loading included underlayment, cabinets, interior doors and countertop (Table 4-3). Plywood was not included as a source because it was covered by underlayment or by floor tile. Loading areas for the sources were taken from Section 3.5 of the pilot-study report, and slopes and intercepts were taken from the pilot-study values provided with the model for underlayment, doors and cabinets. For countertop, industrial particleboard was selected to obtain slope/intercept parameters (average values were used). The intercepts chosen for carpeting and wallboard were predicated on an indoor-air concentration near 40 ppb.

Table 4-3.  Model Inputs (Sources and Sinks) for First (Medium) Loading

Source/Sink

Slope (m/h)

Intercept (mg/m2-h)

Area (m2)

Underlayment

-1.27

0.28

  46

Cabinets

-0.48

0.08

  59

Interior doors

-0.50

0.08

  35

Countertop

-0.70

0.30

   4

Carpeting

-1.30

  0.065

 94

Painted wallboard

-3.00

0.15

420

The modeling results for this case (Table 4-4) are compared with measured values taken at run 4 (28 days after loading), by which time the indoor-air concentrations appeared to have “leveled off” (see Figure A-1 in Appendix A). The addition of carpeting lowered the modeled concentrations slightly, and further addition of wallboard lowered the modeled values by about 10 percent compared to estimates with no sinks. The modeled concentrations for measured conditions, with carpeting and wallboard included, were 5-10 ppb higher than measured values under those conditions.

Table 4-4.  Modeling Results for First Loading

Source/Sink Inputs

Results (ppb) for Base/Measured Conditions

23 ( C, 50 % RH

23.65 ( C, 50.1 % RH

Upstairs

Downstairs

Upstairs

Downstairs

Underlayment, cabinets, doors and countertop as sources

47

40

51

43

Add carpeting as a sink

46

39

49

42

Add wallboard as a sink

42

36

45

39

Measured values (run 3, day 28)

--

--

41

28

4.3.3	Air-out Period after First Loading

For this air-out period, plywood again was the only source and wallboard was the only sink. In this case, however, it was necessary to account for the fact that the wallboard had adsorbed significant mass during the first loading. Some of this mass would be lost during the air-out period, which lasted 7 days, but the amount lost was uncertain. Consequently, the intercept for the first loading (see Table 4-5) was used as an upper bound when developing inputs and half this value was used as a lower bound.

Table 4-5.  Model Inputs for Air-out Period after First Loading

Source/Sink

Slope (m/h)

Intercept (mg/m2-h)

Area (m2)

Softwood plywood

-0.61

0.03

131

Painted wallboard

-3.00

0.15/0.075*

420

*Two runs were made, one with 0.15 as the intercept and one with 0.075.

As shown in Table 4-6, the modeling results with the alternative intercept values for wallboard surround the measured values. The model estimates with the smaller intercept value, to account for the likely possibility that the wallboard had released a fair amount of mass during the air-out period, are closer to the measurement results.

Table 4-6.  Modeling Results for Air-out Period after First Loading

Source/Sink Inputs

Results (ppb) for Base/Measured Conditions

23 ( C, 50 % RH

23.44 ( C, 53.4 % RH

Upstairs

Downstairs

Upstairs

Downstairs

Softwood plywood as a source

10.3

9.0

11.5

10.0

Add wallboard as a re-emitting sink (intercept = 0.15)

34

29

38

33

Change wallboard intercept to 0.075

18

16

20

18

Measured values

--

--

23

26

4.3.4	Second Loading

For the second (high) loading, the sources (Table 4-7) were similar to those for the first loading, but with a larger area for underlayment and with the addition of hardwood plywood paneling as another source. The intercept values chosen for carpet and for wallboard were based on concentration estimates obtained from running the model without any sinks.

Table 4-7.  Model Inputs (Sources and Sinks) for Second (High) Loading

Source/Sink

Slope (m/h)

Intercept (mg/m2-h)

Area (m2)

Underlayment

-1.27

0.28

  94

Cabinets

-0.48

0.08

  59

Interior doors

-0.50

0.08

  35

Countertop

-0.70

0.30

    4

Paneling

-0.98

0.16

  36

Carpeting

-1.30

  0.095

  94

Painted wallboard

-3.00

  0.225

420

Modeled values (Table 4-8) were compared to measurements taken at run 2 (day 12), by which time it appeared that the indoor concentrations had started to “level off” (see Figure A-1 in Appendix A). This earlier time of leveling off, relative to that for the first loading, was likely due to the wallboard sink being substantially “pre-loaded” with formaldehyde mass as a result of the first loading. The modeling results without sinks were 70-75 ppb upstairs and 60-65 ppb downstairs. The addition of carpeting and wallboard as sinks lowered the modeled values by about 10 percent. The modeled values with sources and sinks were about 10 ppb higher than those measured upstairs (differences similar to those for the first loading), and about 15 ppb higher than the measured downstairs values.

Table 4-8.  Modeling Results for Second Loading

Source/Sink Inputs

Results (ppb) for Base/Measured Conditions

23 ( C, 50 % RH

23.48 ( C, 50.1 % RH

Upstairs

Downstairs

Upstairs

Downstairs

Underlayment, cabinets, doors, countertop and paneling as sources

70

60

74

63

Add carpeting as a sink

68

58

72

61

Add wallboard as a sink

63

54

67

57

Measured values (run 2, day 12)

--

--

56

40

4.3.5	Air-out Period after Second Loading

For the air-out period after the second loading, the only sources and sinks again were plywood and wallboard (Table 4-9). As with the first air-out period, it was necessary to account for the fact that the wallboard had adsorbed mass during the second loading and then had lost some of this mass during the air-out period. To accommodate uncertainty in the amount of mass in the wallboard near the beginning of this air-out period, an intercept close to that for the second loading was used as an upper bound, and half that value was used as a lower bound.

Table 4-9.  Model Inputs for Air-out Period after Second Loading

Source/Sink

Slope (m/h)

Intercept (mg/m2-h)

Area (m2)

Softwood plywood

-0.61

0.03

131

Painted wallboard

-3.00

0.19/0.095*

420

*Two runs were made, one with 0.19 as the intercept and one with 0.095.

As shown in Table 4-10, the model results with alternative intercept values for wallboard surround the measured values, and the model estimates with the smaller intercept value are closer to the measurement results. This pattern is the same as that observed for the comparison of modeling and measurement results for the first air-out period.

Table 4-10.  Modeling Results for Air-out Period after Second Loading

Source/Sink Inputs

Results (ppb) for Base/Measured Conditions

23 ( C, 50 % RH

22.83 ( C, 49.6 % RH

Upstairs

Downstairs

Upstairs

Downstairs

Softwood plywood as a source

10.3

9.0

10.0

8.7

Add wallboard as a re-emitting sink (intercept = 0.19)

43

36

41

35

Change wallboard intercept to 0.095

22

19

22

19

Measured values

--

--

27

25

4.3.6	Third Loading

For this repeat of the high loading, the model inputs for sources and sinks (Table 4-11) were the same as those used for the second loading, including the intercepts for carpeting and wallboard.

Table 4-11.  Model Inputs (Sources and Sinks) for Third (High) Loading

Source/Sink

Slope (m/h)

Intercept (mg/m2-h)

Area (m2)

Underlayment

-1.27

0.28

  94

Cabinets

-0.48

0.08

  59

Interior doors

-0.50

0.08

  35

Countertop

-0.70

0.30

    4

Paneling

-0.98

0.16

  36

Carpeting

-1.30

  0.095

  94

Painted wallboard

-3.00

  0.225

420

The measurement results for this loading indicated that concentrations had “leveled off” (see Figure A-1 in Appendix A) by day 7; measured values for run 1 (taken on day 7) therefore were used as a basis for comparison with modeling results. The modeled values were about 10 ppb higher than measured upstairs but about 25 ppb higher downstairs (Table 4-12). One possible explanation for the greater difference downstairs is that the humidity level, which was not measured downstairs, may have been lower than the value used in the model run.

Table 4-12.  Modeling Results for Third Loading

Source/Sink Inputs

Results (ppb) for Base/Measured Conditions

23 ( C, 50 % RH

22.63 ( C, 64 % RH

Upstairs

Downstairs

Upstairs

Downstairs

Underlayment, cabinets, doors, countertop and paneling as sources

70

60

89

76

Add carpeting as a sink

68

58

86

74

Add wallboard as a sink

63

54

80

69

Measured values (run 1, day 7)

--

--

72

43

The results of this assessment collectively indicate that model predictions typically agreed with measurement results within ± 25 percent.

4.4	FIAM-pwp Predictions for Recent Residential Field Monitoring Studies

Recent (i.e., since year 2000) residential formaldehyde field studies of note are summarized in Table 4-13. The first two studies – Offerman et al. (2008) and Hodgson et al. (2000) – both were conducted on new homes, with the Offerman study covering 100+ new single-family homes in California and the Hodgson study covering fewer structures in the eastern and southeastern regions of the U.S. but including both manufactured and site-built homes. The average (geometric mean) formaldehyde concentration indoors was between 30 and 35 ppb for both studies, with maximum values of 117 and 58 ppb reported by the two studies, respectively.

Studies of existing homes in urban U.S. areas by Liu et al. (2006) and Sax et al. (2006) measured lower average (median) formaldehyde concentrations, on the order of 10-15 ppb, and lower maximum values as well, with the highest reported maximum (45 ppb) in a Los Angeles home during the winter. Two Canadian studies (Gilbert et al 2006; Gilbert et al 2005) had nearly identical results; in each case the average (geometric mean) indoor formaldehyde concentration was around 25 ppb and the highest measured concentration was slightly above 70 ppb.

Some other residential environments of interest have been monitored on occasion. For example, during December/January 2007-2008 the CDC measured formaldehyde levels in 500+ structures of the types (travel trailers, park models and mobile homes) used by FEMA for displaced Hurricane Katrina/Rita victims (CDC 2008/2010; DHS 2009). The average (geometric mean) formaldehyde concentration in these structures was 77 ppb (81 ppb in travel trailers) and the maximum measured concentration was 590 ppb. Under an interagency agreement with the CDC, the Lawrence Berkeley National Laboratory (LBNL; Maddalena et al. 2008) studied four FEMA temporary housing units (camper trailers) to assess indoor emissions of aldehydes and other VOCs. Measured formaldehyde levels in these structures ranged from 269 to 753 ppb.

Table 4-13. Summary of Recent Formaldehyde Field Monitoring Studies

Study/Reference	Description (Location and Number/Types of Structures) Formaldehyde Concentration, ppb

Central Value	Range

Offerman et al. 2008	108 new single-family homes in CA	31.1 (median)	3.8 to 116.7

Hodgson et al. 2000	New homes in eastern/SE U.S.:

4 new manufactured homes

7 new site-built homes	Geometric Means:

34

36

21 to 47

14 to 58

Liu et al. 2006	234 homes in Los Angeles County, CA; Elizabeth, NJ; and Houston, TX	16.3 (median)	10.2 to 26.4

(5th - 95th percentiles)

Sax et al. 2006	Inner-city homes:

NY City (46) – winter (W), summer (S)

Los Angeles (41) – Winter (W), fall (F)	Medians:

10 W, 15 S

15 W, 12 F

4-18 W, 5-41 S

6-45 W, 6-26 F

Gilbert et al. 2006	96 homes in Quebec City, Canada	24.0 (geo. mean)	7.8 to 73.2

Gilbert et al. 2005	59 homes in Prince Edward Island, Canada	27.0 (geo. mean)	4.5 to 71.1

Hodgson et al. 2004	4 new relocatable classrooms	8 (average indoor-outdoor level)	4 to 12

(indoor-outdoor)

CDC 2008/2010	519 structures:

Travel trailers (360)

Park models (90)

Mobile homes (69)	77 (geo. mean)

81 (geo. mean)

44 (geo. mean)

57(geo. mean)	3 to 590

3 to 590

3 to 170

11 to 320

Maddalena et al. 2008	4 FEMA camper trailers	463 (average)	269 to 753

References Cited in Table 4-13

CDC. 2008/2010. Final Report on Formaldehyde Levels in FEMA-Supplied Travel Trailers, Park Models, and Mobile Homes. Centers for Disease Control and Prevention. Available at:

  HYPERLINK "http://www.cdc.gov/nceh/ehhe/trailerstudy/assessment.htm#final"  http://www.cdc.gov/nceh/ehhe/trailerstudy/assessment.htm#final . July 2008 (amended December 2010).

N.L. Gilbert, M. Guay, J.D. Miller, S. Judek, C.C. Chan, and R.E. Dales. 2005. Levels and Determinants of Formaldehyde, Acetaldehyde, and Acrolein in Residential Indoor Air in Prince Edward Island, Canada. Environmental Research 99(1): 11-17.

N.L. Gilbert, D. Gauvin, M. Guay, M.E. Héroux, G. Dupuis, M Legris, C.C. Chan, R.N. Dietz, and B. Lévesque. 2006. Housing Characteristics and Indoor Concentrations of Nitrogen Dioxide and Formaldehyde in Quebec City, Canada. Environmental Research 102(1): 1-8.

A.T Hodgson, A.F. Rudd, D. Beal, and S. Chandra. 2000. Volatile Organic Compound Concentrations and Emission Rates in New Manufactured and Site-Built Houses. Indoor Air 10: 178-192.

A.T. Hodgson, D. G. Shendell, W.J. Fisk, and M.G. Apte. 2004. Comparison of Predicted and Derived Measures of Volatile Organic Compounds inside Four New Relocatable Classrooms. Indoor Air 14 (Supplement 8): 135-144.

W. Liu, J. Zhang, L. Zhang, B.J. Turpin, C.P. Weisel, M.T. Morandi, T.H. Stock, S. Colome, and L.R. Korn. 2006. Estimating Contributions of Indoor and Outdoor Sources to Indoor Carbonyl Concentrations in Three Urban Areas of the United States. Atmospheric Environment 40: 2202-2214.

R. Maddalena, M. Russell, D.P. Sullivan, and M.G. Apte. 2008. Aldehyde and Other Volatile Organic Chemical Emissions in Four FEMA Temporary Housing Units – Final Report. LBNL-254E, Ernest Orlando Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Berkeley, CA.

F. J. Offermann, J. Robertson, D. Springer, S. Brennan, and T. Woo. 2008. Window Usage, Ventilation, and Formaldehyde Concentrations in New California Homes: Summer Field Sessions. ASHRAE IAQ 2007 Conference, Baltimore, MD.

S.N. Sax, D.H. Bennett, S.N. Chillrud, P.L. Kinney, and J.D. Spengler. 2004. Differences in Source Emission Rates of Volatile Organic Compounds in Inner-City Residences of New York City and Los Angeles. Journal of Exposure Analysis and Environmental Epidemiology 14 (Supplement 1): S95-S109.

To further assess the predictive capabilities of FIAM-pwp, the model was used to predict the average or central-value formaldehyde concentration measured in two of the above field studies – the Offerman et al. (2008) study of new California homes and the CDC (2008/2010) study of recently constructed travel trailers. In both cases, the predictions were made relying primarily on model defaults, occasionally supplemented in cases where ancillary study measurements suggested that a model input other than the default value might be more appropriate.

As the title of the Offerman et al. (2008) reference indicates, the reported field measurements were conducted in new California homes during the summer season. Neither the average age nor the age distribution of the study homes was reported; they are simply described as “new.” The average temperature and humidity in the homes during monitoring similarly was not reported. The paper does note, however, that these were single-family detached homes, most of which were further described as having no mechanical outdoor air systems and no nighttime ventilation cooling systems. The median air exchange rate in this subset of homes was reported as 0.33 ACH by Offerman el al. (2008).

Given the above descriptions, the inputs/choices shown below in Figure 4-1 were made on the House Screen. Among those choices/inputs, the following are changes to model default values:

“Standard Conditions” for temperature (23 °C) and relative humidity (50 %)

Single-family detached home conceptualized as a single zone, with airflows edited to yield an air exchange rate of 0.33 ACH.

Figure 4-1. FIAM-pwp House-Screen Inputs Used to Model Study of New California Homes.

For the Source Screen (see Figure 4-2), model defaults were used for all PWPs. The only change made was the reassignment of sources associated with Zone 2 to be located in Zone 1, consistent with the single-zone conceptualization of the house as noted above.

Figure 4-2. FIAM-pwp Source-Screen Inputs Used to Model Study of New California Homes.

As shown in Figure 4-3, results of the model run for this case included a predicted concentration of 39.2 ppb (48.4 µg/m3) for these homes following construction. By comparison, the authors of the paper reported a median concentration of 31.1 ppb (38.3 µg/m3; neither the arithmetic nor the geometric mean was reported) for the subset of new homes modeled here. As noted above, the age of the monitored houses was not reported in the paper, other than their being “new.” If the average house age was six months, for example, then the model prediction of 32.6 ppb (40.3) µg/m3 would apply; this prediction agrees closely with the reported median value. The model prediction for these homes at an age of 12 months was 27.4 ppb (33.9 µg/m3.

Figure 4-3. FIAM-pwp Results for Modeling of New California Homes.

Travel trailers accounted for nearly 70 % of the structures that were monitored by CDC (2008/2010).

The structure type selected on the House Screen was camper trailer using model defaults, including an air exchange rate of 0.2 ACH, with the single exception of temperate and humidity, for which the same values were used as for the single-family detached case. For the Source Screen (see Figure 4-4), model defaults were used for all PWPs.

Figure 4-4. FIAM-pwp Source-Screen Inputs Used to Model CDC Study of Travel Trailers.

The model prediction of 78.3 ppb (see Figure 4-5) agrees closely with the geometric mean (81 ppb) reported by CDC. However, from the information given in the CDC report, the trailers were approximately one to two years old when monitored. Thus, the predicted value of 52.1 ppb at an age of 12 months would be more appropriate. The 12-month predicted value is about a third lower than the geometric mean of the field measurements. One possible reason for the difference is that some of the trailers monitored by CDC may have included import products (e.g., for wall paneling or cabinets sides/back); the maximum monitored concentration of 590 ppb among the CDC travel trailers supports this speculation. If, for example, the intercept for HWPW were doubled to account for this possibility, then the predicted concentration at 12 months would be 66.2 ppb.

Figure 4-5. FIAM-pwp Results for Modeling of Travel Trailers.

The modeling results indicate that FIAM works reasonably well for its primary intended purpose – prediction of concentrations in new residential structures shortly after their construction.

Appendix A

Summary of EPA Formaldehyde Pilot Study

A.1	STUDY OBJECTIVES AND DESIGN

At a public meeting in January 1993, EPA representatives outlined a plan for a proposed formaldehyde (HCHO) study that was to be conducted in two phases – a main study and a pilot study. The main study was to involve testing using passive monitors in 108 newly constructed conventional and manufactured houses located throughout the United States. A smaller pilot study was to be conducted first to evaluate the feasibility and logistical considerations of the experimental design for the larger main study.

In September 1994 the National Particleboard Association (NPA) signed a Cooperative Research and Development Agreement (CRDA) with EPA to fund a pilot study in newly constructed conventional and manufactured houses. The general purpose of the pilot study was to evaluate methods used to measure the contribution of UF-bonded building materials to indoor HCHO concentrations in newly constructed conventional and manufactured houses.

The specific objectives of the pilot study were to:

Test logistical considerations relevant to carrying out experimental procedures for the testing program in a single conventionally-built single-family house and in several manufactured houses.

Demonstrate that experimental variables or conditions likely to affect formaldehyde concentrations in new houses (i.e., UF-bonded wood product emission characteristics and loading rates, temperatures and indoor air exchange rates) can be controlled, individually and jointly varied, held sufficiently constant, and that the response can be measured to a specified precision.

Demonstrate that test results can be obtained across a range of different experimental conditions, similar to that which can be present in new houses.

Estimate the extent of variability of the experimental results and the variation with changes in experimental conditions.

Determine how to account for, or to eliminate or minimize, residual formaldehyde carryover between test runs in the conventional house due to effects of inherent sinks.

Evaluate the ability to control and vary the air exchange rate of houses using an adjustable mechanical air handling system.

The study was guided by a Quality Assurance Project Plan (QAPP) with a detailed description of the experimental design and variables, monitoring protocols, and quality assurance/control procedures that would be employed. According to the QAPP, the pilot study would include one unoccupied, conventionally built, single-family house and four unoccupied manufactured houses. Four manufactured houses were specified in the pilot study because it was not practical to install and remove products in a manufactured house. The conventional house was to be a two-story house on a slab or crawlspace. The manufactured-house portion of the pilot study eventually was dropped due to resource limitations.

The QAPP also specified that the following variables would be evaluated in the pilot study:

Product emission characteristics: Only “medium” emitting products were to be used. Emissions from particleboard and from plywood wall paneling, as measured by ASTM method E 1333 (cited previously in this document) were to be between 0.12 and 0.14 ppm. Because there were no established protocols for measuring formaldehyde emissions from kitchen/bathroom cabinets, commercially available cabinets constructed with “medium” emitting materials (melamine-wrapped particleboard) were to be used.

Product loading rate: Two different loading combinations of products – Medium and High (defined later) – were to be installed in the house.

Environmental conditions in the house:

Temperature of 75 °F

Ventilation rate of 0.5 air changes per hour (ACH)

Relative humidity in the house, while not a controlled variable, was targeted at 50 percent. Air leakage was to be determined through blower-door tests, with efforts to make the house as airtight as possible. Ventilation rates were to be controlled by a mechanical heat recovery ventilator (HRV) attached to the heating and air conditioning (HAC) system. Air exchange rates were to be measured by two tracer gas methods – constant release of perfluorocarbon tracers (PFTs, EPA Method IP-4A) and periodic injection/decay of sulfur hexafluoride (SF6, EPA Method IP-4B). All USEPA methods cited on this page have been compiled in a compendium.

Four product loadings were to be used – two Medium and two High. Prior to loading the products in the house, a baseline value for the house without any experimental UF-bonded wood products was to be determined. The products then would be installed in the house and indoor formaldehyde concentration measurements taken over approximately a 30-day period. At the completion of 30-day period, the products were to be removed from the house. The house would be allowed to “air out” for a period of time until a new equilibrium level (baseline) was reached, after which the next set of products would be installed. The order of the loading configurations in the house was to be randomized, with the single constraint that Loadings 1 and 2 would be different (i.e., one High and one Medium).

Indoor and outdoor formaldehyde concentrations (24-hour time-integrated values) were to be measured by EPA method IP-6A (Solid Adsorbent Cartridge) 7, 12, 28, and 33 days after products were installed in the house. If necessary, additional testing could take place to confirm any trends or unexpected results. Readings on days 12 and 33 were considered statistical replicates of readings on days 7 and 28, respectively. Indoor formaldehyde concentrations were to be measured in the kitchen, living room, upstairs bedroom, basement, and outdoors. One duplicate sample was to be collected on each sampling occasion, at a location to be varied systematically.

Product emission tests were to be conducted in a large chamber in accordance with ASTM E 1333, at three different air exchange rates. Because there were no established protocols for large-chamber testing of doors and cabinets, the following loading rates were be used:

Doors – five doors, at a total loading rate of 0.125 ft2/ft3

Kitchen cabinets/countertops – one base and one wall cabinet with doors closed, at a loading rate of 0.133 ft2/ft3. A section of countertop was to be placed on the base cabinet during testing.

The above loading rates were similar to those established by the Department of Housing and Urban Development (HUD) for large-chamber testing of particleboard and industrial panels.

For sink-effect testing of painted gypsum wallboard and carpet/padding, products were to be placed in a small clean environmental chamber. A known concentration of formaldehyde gas was to be injected into the chamber. By accurately measuring time-varying concentrations in the chamber, it could be determined whether the material was absorbing formaldehyde gas and then re-emitting it after the source was turned off.

A.2	STUDY METHODS

Securing a house builder or owner who was willing to participate in the study proved to be more difficult and costly than anticipated, due mainly to the constraint that the house could not be occupied during the test period. A homeowner was located in Centreville, MD, who was building a rental house and was willing to lease it for as long as needed. The house was a conventionally built, 1326 ft2, two-story Cape Cod style with a full basement (volume of 168 m3). The QAPP had called for a house with crawl space, but efforts to find such a house in the study area were unsuccessful. The total volume of the finished living space was 10,746 ft3 (304 m3). The first floor of the house (712 ft2 floor area) had 5931 ft3 (168 m3) of living space that consisted of a living room, kitchen, bathroom/laundry room, and bedroom. The second floor of the house (614 ft2 floor area) had 4815 ft3 (136 m3) of living space that consisted of two bedrooms and a bathroom. The door from the first-floor finished living space to the unfinished basement was sealed shut during the entire project. The house contained no furniture or draperies.

Industry representatives were responsible for procuring all pressed-wood products that would be used in the pilot study. Sufficient quantities of 5/8” particleboard underlayment, 3/4” industrial particleboard for countertops, 1/4” hardwood plywood wall paneling (3-ply birch face, tropical hardwood back and core with 7 cut grooves along the length of each panel to simulate random-width lumber planking), interior partition doors, and kitchen and bathroom cabinets were obtained from member companies or participating associations, or were purchased at local building supply centers. Emission characteristics of the particleboard and plywood wall paneling used in the study were determined prior to selecting the materials for testing.

Initial emission characteristics of the products used in the study (see Table A-1) were determined by ASTM E 1333 at 0.5 ACH. All products were stored in a controlled-access warehouse until they were installed in the house. During storage, products were wrapped in 6-mil plastic to minimize formaldehyde off-gassing. It was discovered during the study that temperature control in the warehouse was marginal and that temperatures ranged up to 85 ° F.

Products were installed in the house according to manufacturers’ recommended installation instructions, and conventional practices were followed. The particleboard underlayment was installed with screws for easy removal. The kitchen and bath cabinets were screwed tightly against the wall. The plywood wall paneling was nailed to the wall to minimize damage to the gypsum wallboard.

Table A-1. Initial Emission Characteristics of Products Used in the Pilot Study

Product	Emissions, ppm	Loading Rate, ft2/ft3

Particleboard Underlayment	0.144	0.130

Plywood Wall Paneling	0.114	0.290

Cabinets	0.053	0.133

Interior Doors	0.052	0.125

Loading areas for pressed-wood products are shown in Table A-2. For the Medium loading scenario, particleboard underlayment was installed on the first floor, along with interior doors on both floors and a full set of kitchen/bathroom cabinets and countertops. For the High loading scenario, particleboard underlayment was installed on both the first and second floors. In addition, twelve 4’ X 8’ sheets of plywood wall paneling were installed. To establish a relatively uniform loading and to avoid using partial panels, four full-size sheets were installed in an upstairs bedroom, in the downstairs bedroom, and in the living room. Interior doors and a full set of kitchen and bathroom cabinets and countertops (same number as for Medium loading) also were installed. The total exposed surface area for cabinets was calculated to be 631 ft2 (59 m2). Particleboard underlayment was not installed in the kitchen and bathroom areas of the house, as those areas were covered by vinyl sheet goods that had been permanently installed during final preparation of the house before field testing was initiated.

Table A-2. Loading Areas for Pressed-wood Products at the Conventional House

Component

Loading Area, ft2

1st Floor

2nd Floor

Medium Loading

High

Loading

Medium

Loading

High

Loading

Underlayment

496.2

496.2

---

519.3

Paneling

---

256.0

---

128.0

Doors

203.6

169.6

Countertop

  37.9

     5.65

Blower-door tests indicated that the house had numerous leaks in the building shell and between the first floor and basement. Air leakage sites were identified (service penetrations between the basement and first floor and along the base plate) and sealed with caulk and foam. Numerous leaks also were found in the forced-air HAC distribution system. Sealing procedures reduced the leakage rate by more than 50 percent, from ~ 10 ACH at 50 Pa (corresponding to ~ 0.5 ACH under moderate environmental conditions) to ~ 4 ACH at 50 Pa.

Initial study plans did not include measurement of formaldehyde concentrations in the basement, because it was thought that the combination of house sealing procedures and a closed interior door at the top of the stairwell to the basement would minimize air communication with the remainder of the house. However, during tracer gas studies to characterize the air exchange rate for the house it became obvious that tracer injected into the living area was being transferred to the basement. Consequently, it was decided to include formaldehyde measurements in the basement. In addition, PFT sources and samplers were configured so that the average airflow rate between the basement and living area could be quantified during each sampling event.

Following initial baseline testing, products for Loading 1 (Medium) were installed and indoor concentration levels were measured in accordance with the protocols outlined in the QAPP. It became evident during this time that there was difficulty in controlling relative humidity levels in the house, which reached over 70 percent. Humidity levels were lowered to the desired range by adding additional dehumidification equipment in the house. Because high humidity causes higher formaldehyde emissions, the house was declared to be in an “upset condition” during this time and it was decided that Loading-1 products should be left in the house until conditions stabilized. The final readings for Loading 1 were taken 78 days after product loading.

It also was determined during this time that resource constraints would not permit the full implementation of the loading schedule established in the study plan, which was modified for conduct of only three loadings in the house – one Medium and two High loadings. In addition, the air-out period between successive loadings was fixed at seven days instead of waiting for formaldehyde levels to reach equilibrium.

Following the removal of Loading-1 products from the house and a seven-day airing-out period, Loading-2 (High) products were installed. Formaldehyde concentrations were measured on days 7, 12, 28, and 33. Following removal of Loading-2 products from the house and a seven-day airing-out period, Loading-3 (High) products were installed. Formaldehyde concentrations again were measured on days 7, 12, 28, and 33 after loading. Following removal of Loading 3 products, the house was returned to the homeowner.

A limited amount of sink-effect testing was conducted as part of the pilot study. From results of the laboratory sink-test results and results from Loadings 1, 2 and 3, it appeared that the gypsum wall board was acting as a significant sink. Because the exposed surface area of the wallboard was greater than all of the UF-bonded products installed in the house, it was considered critical to fully characterize the sink effect behavior of painted gypsum wallboard. It also was considered important to determine whether the carpet/padding used in the house was acting as a sink or had any barrier effect on formaldehyde emissions from the particleboard underlayment.

The original protocol for “barrier testing” was modified to evaluate the floor system with both particleboard underlayment and carpet/padding, instead of just the carpet/padding. A sample of particleboard underlayment was placed in a stainless-steel pan and inserted in a small chamber. Formaldehyde concentrations in the chamber were measured continuously with a real-time (Interscan) analyzer. As a separate test, a second sample of particleboard with carpet/padding directly above it was placed in a stainless-steel pan and inserted in the chamber. Differences in the concentration profiles for the two tests would reflect the barrier effect of the carpet/padding used in the pilot study. To minimize the inherent variability within a piece of particleboard, specimens used for these tests were prescreened via small-chamber emission tests – the two pieces with the closest emission rates were used for the tests.

A.3	STUDY RESULTS

The results of formaldehyde, temperature, humidity and air-exchange measurements during the formal “runs” associated with each loading, as well as their respective baseline periods, are compiled in Table A-3. Formaldehyde concentrations measured in the upstairs rooms generally were similar to one another and higher than those measured in the basement. The highest concentration measured in the house – 76 ppb – was in the kitchen during Loading 3 (High). The monitoring results collectively indicate that, for all three loadings, indoor HCHO concentrations had peaked by the time of measurements taken 33 days after product loading. The formaldehyde results also indicate that monitored levels for Loadings 2 and 3 generally were consistent with one another and that these “high” loadings had higher HCHO levels (but also a higher baseline) than the “medium” loading (Loading 1).

Although measured air exchange rates generally were in the target range of 0.4 to 0.6 ACH, the PFT estimates consistently were higher than those based on SF6. One possible reason for the discrepancy is the inherent difference between the two measurement technologies. The SF6 method involves periodic injection and mixing of the tracer through the HAC system, followed by real-time analysis as the concentration declines. The PFT method relies on a near-constant release of tracers from multiple locations near the perimeter of the house, with time-integrated sampling over a 24-hour period.

Table A-3.  Summary of Monitoring Results for Loadings 1, 2, and 3

Runa

Formaldehyde Concentration, ppb

Temperature, (F

RH, %

Air Exchange, ACH

LR

KIT

BR

BMT

AMB

LR

KIT

BR

BMT

AMB

LR

2ND

AMB

SF6

PFT

Loading 1 (Medium)

Baseline

9.1

9.8

9.5

9.1

1.3

75.7

75.8

74.0

63.4

49.0

22.8

24.4

55.2

--

0.50

1

27.5

29.9

20.1

--

1.0

73.8

73.4

73.2

68.5

56.9

43.2

41.0

60.2

0.44

0.54

2

29.6

31.3

29.9

26.5

7.0

73.8

73.6

73.4

66.7

52.4

46.2

43.2

76.8

0.44

0.54

3

41.7

43.9

36.3

28.2

2.1

75.1

75.0

74.9

71.1

69.6

63.1

60.2

93.9

0.40

0.54

4

36.8

39.4

31.1

--

1.7

75.5

74.8

73.4

73.1

66.0

50.4

49.8

60.6

0.40

0.57

Loading 2 (High)

Baseline

23.0

23.7

22.1

25.7

2.8

75.2

73.1

74.3

77.0

84.4

54.5

52.3

80.3

0.39

--

1

60.1

60.8

60.5

39.7

2.9

75.3

73.5

74.5

76.2

81.5

57.1

55.5

88.2

0.38

0.61

2

55.8

58.1

54.7

40.0

2.3

75.1

73.4

74.3

75.4

80.1

50.9

49.3

74.1

0.38

0.71

3

46.7

48.5

53.3

38.0

1.4

74.4

73.9

75.6

75.7

75.4

50.7

43.8

71.2

0.36

0.59

4

39.0

40.8

48.1

30.7

0.9

73.4

73.2

73.2

73.6

63.1

51.6

43.2

71.6

0.39

0.60

Loading 3 (High)

Baseline

26.0

25.8

27.7

25.0

<1.0

73.3

72.8

73.3

73.3

61.4

54.9

44.3

85.0

0.41

--

1

71.9

76.1

65.6

42.6

1.1

75.0

73.2

72.5

73.6

76.1

62.7

65.3

95.1

0.39

0.69

2

53.8

55.2

54.7

29.9

1.1

72.3

72.4

72.0

70.7

60.3

49.7

47.1

86.7

0.36

0.64

3

43.2

46.2

39.5

20.3

1.1

71.7

71.8

69.5

66.6

49.1

43.8

43.7

87.2

0.42

0.62

4

42.3

40.4

44.1

22.8

1.4

71.7

71.9

70.7

66.9

55.4

46.1

44.9

88.8

0.35

0.53

	Legend:						a Run 1 occurred 7 days after product loading;

	LR = living room; KIT = kitchen;			  Run 2 occurred 12 days after product loading;

	BR = bedroom; BMT = basement;		  	  Run 3 occurred 28 days after product loading;

	AMB = ambient;	2ND = second floor.		  Run 4 occurred 33 days after product loading.

Upstairs measurements (average of kitchen, living room and bedroom locations) for the three loadings are plotted in Figure A-1 against elapsed time after UF-bonded wood products were installed (day “zero” indicates baseline measurements). The curvature of the lines is due to the spline fit that was applied and is not meant to imply that values between measurement points can be readily interpolated. The figure illustrates the general consistency across Loadings 2 and 3 and their differences from Loading 1. Although concentrations for Loading 1 are similar to those for Loadings 2 and 3 toward the end of their respective test periods, indoor humidity levels were relatively high near the end of Loading 1.

Figure A-1. Upstairs Formaldehyde Concentrations over Time for Three Loadings.

Differences in baseline levels and in the general shape of the time series for Loading 1 versus Loadings 2 and 3 can be explained partly by the wallboard sink effect. The wallboard sink was largely “empty” at the outset of Loading 1 but was largely “pre-loaded” at the outset of Loadings 2 and 3, as reflected in the higher baseline values for the later loadings. The time series for Loadings 2 and 3 have a shape consistent with that of an exponentially declining emitter, as would be expected when the dominant sink (wallboard) has been pre-loaded and becomes a “net zero emitter,” such that the declining rate of emissions from aging wood products drives the concentration profile. For Loading 1, however, this profile is dampened by the relatively large mass being absorbed by the wallboard sink in an “unloaded” state. Some of the difference in baseline values for Loading 1 versus Loadings 2 and 3 also may be due to the relatively low humidity level at the time when baseline measurements were taken for Loading 1.

The key measurement parameter for the study, formaldehyde by the DNPH method, was in control across all measurement periods. QA spikes indicated that recoveries were consistently in the range of 90-110 percent, well within the accuracy goal of ±20 percent. Results of duplicate DNPH samples indicated a combined sampling and analytical precision of ±10 percent or better, again well within the corresponding data quality objective. The standard deviation across the high loadings, for measurements at the same location and at the same elapsed time since loading of UF-bonded wood products, was not much larger than that for duplicate measurements (i.e., at the same time and location within any given loading). This finding points to the repeatability of high-loading results for the conventional house, after the sinks were pre-loaded as a result of the preceding medium loading.

Emission rates for UF-bonded wood products that were installed in the pilot study house, based on large-chamber concentrations that were adjusted to standard conditions of 77 ( F and 50% RH per ASTM E 1333, are listed in Table A-4. Each product was tested at target air exchange rates of 0.25, 0.5 and 1.0 ACH. Two patterns that were evident for all products are noteworthy. First, as the air exchange rate is increased, the emission rate also increases, but at a rate that is less than proportional to the increase in air exchange. This trend is indicative of a concentration “backpressure” effect, as applied in the Matthews model. Second, for each product the emission rate was lower for products used for later loadings (products were tested near the time of each loading). These results indicate that some emissions decay likely occurred during storage, even though products were wrapped in plastic. The elevated temperature in the warehouse may have accelerated the decay process somewhat.

Table A-4.  Computed Emission Rates for UF-Bonded Products

Loading

Emission Rate, µg/m2-h

Underlayment

Paneling

Cabinets

Doors

At Target ACH of 0.25a

1

2

3

104.9 (0.25 ACH)

99.2 (0.25 ACH)

90.4 (024 ACH)

Not Used

42.9 (0.25 ACH)

32.9 (0.25 ACH)

45.6 (0.17 ACH)

45.2 (0.24 ACH)

45.7 (0.25 ACH)

52.0 (0.24 ACH)

Not Tested

49.9 (0.25 ACH)

At Target ACH of 0.50

1

2

3

178.3 (0.50 ACH)

162.6 (0.50 ACH)

149.9 (0.51 ACH)

Not Used

72.3 (0.50 ACH)

56.8 (0.50 ACH)

77.1 (0.51 ACH)

69.9 (0.50 ACH)

68.5 (0.50 ACH)

74.2 (0.50 ACH)

Not Tested

68.4 (0.51 ACH)

At Target ACH of 1.0

1

2

3

221.9 (1.01 ACH)

200.6 (0.99 ACH)

190.2 (1.01 ACH)

Not Used

104.9 (0.99 ACH)

77.0 (1.01 ACH)

82.8 (1.00 ACH)

73.4 (0.99 ACH)

74.9 (1.01 ACH)

79.9 (1.00 ACH)

Not Tested

74.2 (1.00 ACH)

a Actual air exchange rates during each test are given in parentheses.

Other products used in the house were assessed for formaldehyde emission characteristics. For the paint used on the wallboard and interior doors at the study house, the manufacturer’s data indicated that the wallboard paint contained 0.001% formaldehyde by weight and the door paint contained 0.007% formaldehyde. A carpet/padding sample was sent to EPA’s Air and Energy Engineering Research Laboratory (AEERL) in Research Triangle Park for small-chamber testing. Results of the chamber tests, conducted at 0.5-0.55 ACH, 74 ( F and 55-60 % RH, indicated an emission rate of 1.4 µg/m2-h for the carpet and the same rate for the padding (after subtracting the chamber background) at an elapsed time of 24 hours following insertion in the chamber, or an emission rate of 2.8 µg/m2-h for these two constituents combined. The combined emission rate is one to two orders of magnitude lower than that for UF-bonded wood products.

Small-chamber tests were conducted to evaluate sink characteristics of the carpet and padding.  Two tests were conducted under identical air exchange rates of 1.5 ACH, but with different formaldehyde concentrations in the input stream because the rate of adsorption to the sink was suspected to be a function of the air concentration. In both tests, a 7.1-inch square piece of carpet and padding was placed in a tight-fitting aluminum pan with edges equal to the depth of the carpet and padding. The pan containing the carpet and pad was then placed horizontally on the chamber floor. The chamber was sourced with a formaldehyde stream of 0.2 ppm during the first test and 0.12 ppm during the second. Comparison of the theoretical (concentrations that would be expected in the absence of sinks) and measured concentrations indicated that formaldehyde was adsorbed by the carpet, and the trend in the data appeared to reflect a first-order removal process.

Chamber tests for gypsum wallboard were conducted to evaluate its sink characteristics. As with the carpet tests, these two tests were conducted under identical conditions with the exception of the formaldehyde feed-stream concentration, to evaluate the effect of concentration on the rate of mass transfer to and from the wallboard. For each test, two 10.5-inch square pieces of painted wallboard were securely fastened back-to-back and edge sealed with sodium silicate, leaving a total of 220.5 square inches of exposed wallboard surface area. The wallboard was then placed in the center of chamber in a vertical position, supported by stainless steel wire. The chamber was sourced with a formaldehyde stream of 0.2 ppm during the first test and 0.12 ppm for the second, at 1.5 ACH. The resulting data from these tests indicated that the sink effect was more pronounced for wallboard than for the carpet/padding ensemble. The concentration data were fit to a Langmuir isotherm model to estimate adsorption and desorption rate constants for the two types of sinks.

Tests to evaluate the behavior of underlayment both with and without a carpet/padding barrier were conducted under identical chamber conditions using a tight-fitting aluminum pan with edges equal to the depth of the underlayment, carpet and padding. In the first test, a 7.1-inch square piece of underlayment was placed in the pan with nothing above it. In the second test, a 7.1-inch square piece of underlayment was placed in the pan with an equally sized piece of padding and carpet placed above it. For both tests, the pan was then placed horizontally on the chamber floor. The resulting data indicated that the underlayment was releasing formaldehyde.  While it was tempting to conclude from the results that the carpet and padding had no effect on the emission of formaldehyde, the carpet/padding sink test described above indicated otherwise.

A.4	STUDY CONCLUSIONS

The following conclusions, primarily related to the objectives given in Section A.1, were reached as a result of the pilot study:

Some logistical difficulties were encountered that prevented the study from being completed as outlined in the QAPP. Among the greatest difficulties were locating a study house and maintaining humidity levels in the house within the prescribed range. Humidity was not a primary experimental variable for the study, but was considered to be an important covariate that should be tightly controlled. Logistical aspects such as acquiring, storing and accessing the materials associated with house loading went remarkably smoothly, due in part to the high level of cooperation from various industry representatives and their close working relationship with the study team.

Little difficulty was encountered in controlling most experimental variables at the study house. The primary variables – product loading rate, emission rate, temperature, and air exchange – all were generally kept within their respective target ranges. Some emissions decay was evident for wood products stored for successively later loadings.

It was demonstrated that different test results could be obtained across different experimental conditions and that sufficient precision in measurement response could be obtained. Differences across the experimental conditions (medium versus high loading) could be distinguished, although these differences were partially dampened by the substantial sink effect of the gypsum wallboard. Appropriate precision was obtained largely because of the consistently high resolution, accuracy and precision for the sampling method (solid adsorbent cartridge) with a 24-hour sampling duration.

The study data were marginally sufficient for estimating the extent of variability of results and the variation with changes in experimental conditions. The limited number of loadings, coupled with the unique circumstances of the first loading (little mass in the indoor sinks at the outset), made it difficult to properly estimate the variance component associated with repeats of the same loading configuration. However, it was demonstrated that the variance across repeats of the high loading, for a specific sampling location at the same elapsed time relative to loading of the house, was only marginally higher than the variance for duplicate formaldehyde samples.

Formaldehyde carryover between successive tests at the conventional house, due to inherent sinks, was not trivial. The sink effect, due largely to adsorption of formaldehyde by painted gypsum wallboard, was not eliminated by the prescribed “airing out” of the house. The monitoring results, however, did suggest that baseline formaldehyde values were reasonably reproducible once the house had been loaded with UF-bonded wood products.

The ability to control and vary the air exchange rate of the conventional house using a heat recovery ventilator (HRV) was demonstrated. This ability was demonstrated for two of the three target air exchange rates (0.2 and 0.5 ACH) planned for the full study; the third target (1.2 ACH) could not be addressed because the HRV lacked sufficient capacity. Achieving the lower target of 0.2 ACH was made possible by sealing procedures that substantially reduced the air leakage of the house and, thus, the sensitivity of its air exchange rate to weather conditions.

Appendix B

Model Sensitivity

B.1 	ANALYSIS BY MATTHEWS

Prior work by Matthews and colleagues at Oak Ridge National Laboratory during the mid-1980s forms the primary basis for FIAM-pwp, as noted in Section 1 of the main document. The researchers generated a series of reports documenting their work for the U.S Consumer Product Safety Commission. One of these reports included a sensitivity analysis for formaldehyde concentration and emission-rate models; the concentration model was very similar to that used for FIAM-pwp, including temperature and humidity adjustments. The measure of sensitivity was the fractional change in model output per unit change in each coefficient; for example, a sensitivity of 0.1 would mean that a 10% change in the model is expected with a 100% change in the coefficient.

The results of the sensitivity analysis depended on both the values of the model coefficients determined for a given pressed-wood product data set and the environmental conditions that are substituted into the model. Results of the analysis indicated that the concentration model was most sensitive to values for the coefficients representing the temperature and relative humidity (RH) dependence, regardless of product type. The highest value for the sensitivity measure, for MDF, was 0.45 for temperature; similar, but somewhat lower, sensitivity values were found for particleboard and paneling. The highest sensitivity value for RH was 0.40, for paneling.

B.2 	ANALYSIS BY VERSAR

Versar performed sensitivity analysis on a prior, mathematically identical, version of FIAM-pwp to guide the choice of factors to be varied and the relative number of variations for each as part of an earlier set of model runs. This analysis was conducted for two cases available in the prior version of FIAM-pwp – a conventional home (i.e., the conventionally built single-family detached home used in the EPA formaldehyde pilot study; see Appendix A) and a manufactured home. The conventional home, with a volume of 471 cubic meters, is conceptualized as having two zones whereas the manufactured home is a single-zone structure with a volume of 222 cubic meters.

As summarized in Table B-1 for the conventional home, ten factors (input parameters) were systematically varied for the sensitivity analysis. The background concentration and average concentration encountered when an individual is away from home both were set to zero for this analysis, so that modeled concentrations and exposures would reflect only the impact of PWPs in the house. The source and sink loading areas in the table represent one of the actual loading conditions that were used in the pilot study.

Sensitivity was examined by varying each input parameter – one at a time – by 20 percent in each direction (i.e., 20 % lower and 20 % higher) from the base condition shown in Table B-1. Five model outputs were examined for sensitivity to the ten factors: (1) initial concentration in zone 1 (upstairs); (2) concentration 24 months later in zone 1; (3) average daily concentration (ADC); (4) average daily dose (ADD); and (5) % of time the concentration is ≥ 0.01 ppm (10 ppb). Values of these outputs for the base condition are listed in Table B-2.

Table B-1. Input Values for Sensitivity Analysis – Base Condition for Conventional Home

Input Parameter(s)	Base Value(s)

Air Exchange Rate (ACH)	0.59

Emissions Half Life (years)	2.92

Temperature (°C)	23

Relative Humidity (%)	50

Source Loading Areasa (m2) 	46, 59, 35, 4

Sink Loading Areasa (m2)	94, 420

House Age at Move-in (years)	5

Years Lived in House	5

Hours in House on Weekday, Weekend Day	15, 18

Inhalation Rate (m3/day)	13.3

a Sources are underlayment, cabinets, interior doors, and countertop; sinks are carpet/padding and painted wallboard.

Table B-2. Model Results for Base Condition for the Conventional Home

Initial Conc in Zone 1,

mg/m3	Conc 24 Months Later in Zone 1, mg/m3	Average Daily Concentration, mg/m3	Average Daily Dose,

mg/kg-day	% of Time Concentration  ≥ 0.01 ppm

0.0514	0.0320	0.0061	0.0011	13.7

Changes in each model output associated with the change in each input, in each direction, were averaged and then expressed as a percent change from the result for the base condition. The sensitivity results are summarized in Figure B-1 as the percent change for each model output associated with a 20 % change in each input. Certain inputs, by definition, do not affect certain model outputs. For example, the emissions half life has no effect on the initial concentration and the inhalation rate affects only the average daily dose. Based on this analysis, the most sensitive input parameters, in order of relative sensitivity (most sensitive first), are indoor temperature, emissions half life, house age, and indoor humidity.

Figure B-1.  Relative Model Sensitivity for the Conventional Home.

For the manufactured home (Table B-3), the same ten factors were systematically varied for the sensitivity analysis. As with the conventional home, the background concentration and average concentration encountered when an individual is away from home both were set to zero for the analysis. A broader set of PWPs, with generally higher loading rates, was used for this case. As a result, the modeled initial concentration was about three times as high as the conventional home case (Table B-4). Due to the higher concentration, a higher threshold (0.02 ppm) was used to examine the relative frequency of higher concentrations. As with the conventional home, the most sensitive input parameters for this case are indoor temperature, emissions half life, house age, and indoor humidity (Figure B-2).

Table B-3. Input Values for Sensitivity Analysis – Base Condition for Manufactured Home

Input Parameter(s)	Base Value(s)

Air Exchange Rate (ACH)	0.50

Emissions Half Life (years)	2.92

Temperature (°C)	23

Relative Humidity (%)	50

Source Loading Areasa (m2) 	95, 53, 26, 3, 43, 36

Sink Loading Areasa (m2)	72, 158

House Age at Move-in (years)	5

Years Lived in House	5

Hours in House on Weekday, Weekend Day	15, 18

Inhalation Rate (m3/day)	13.3

a Sources are PB underlayment, paneling, interior doors, countertop (particleboard),  cabinets, and closet shelving (PB/MDF); sinks are carpet/padding and wallboard.

.

Table B-4. Model Results for Base Condition for the Manufactured Home

Initial Conc in Zone 1,

mg/m3	Conc 24 Months Later in Zone 1, mg/m3	Average Daily Concentration, mg/m3	Average Daily Dose,

Figure B-2.  Relative Model Sensitivity for the Manufactured Home.

Appendix C

Basis for Emission Classes

As described in Sections 2.3.1 and 2.3.3 of the main document, default values for FIAM emission-rate parameters have been developed for four emission classes: Baseline; CARB1; CARB2; and NAF. Further details on the basis for these default values are described below, under the headings of Baseline Emissions Class (Section C.1) and Reduced Emissions Classes (Section C.2; includes CARB1, CARB2, and NAF). This appendix has been extracted/adapted from the draft formaldehyde exposure assessment report cited in Appendix B (see Section B.2).

C.1	BASELINE EMISSIONS CLASS

Between June and October 2010, EPA administered a survey to domestic manufacturers of composite wood panels; the survey asked about both current and planned emission levels. Because many CWP manufacturers are in the midst of modifying their production technology and raw materials to achieve compliance with Phase 2 of the CARB Air Toxics Control Measure (ATCM), using current emission levels to estimate emission levels in 2013 would not accurately reflect the 2013 baseline. Instead, baseline emission levels were estimated using responses to a survey question about emission levels that mills planned to achieve within the next three years. These levels were weighted by production levels that mills reported in the survey to estimate average emission levels by certification standard. The survey data also were used to estimate the share of total production volume represented by products meeting each of the emission standards. The survey results are reported in Table C-1. For comparison purposes, the CARB emission limits are shown in Table C-2.

Table C-1. Baseline Emission Levels (2013) For Domestically Produced CWPs,

by Product Type and Emissions Certification Standard

Emissions Standard	Product Type

	HWPW	MDF	PB

Weighted Average Emissions (ppm)

None	0.058	---	0.058

CARB 1 a	---	---	0.090

CARB 2	0.032	0.082	0.057

CARB ULEF b

0.024	0.042

CARB NAF c	0.013	0.035	0.013

Share of Production

None	0.4%	---	0.2%

CARB 1	---	---	1.8%

CARB 2	60.2%	86.1%	88.5%

CARB ULEF

4.6%	2.8%

CARB NAF	39.4%	9.3%	6.7%

a Some mills producing products currently certified under CARB Phase 1 (CARB 1) reported that they would continue this product line after the CARB Phase 2 (CARB 2) effective date.

b Hardwood plywood mills meeting CARB 2 and CARB Ultra Low Emission Formaldehyde (ULEF) were grouped together in the CARB 2 category. Several HWPW mills appeared to be meeting CARB ULEF standards but did not report this in their response. For example, they listed the certification standard as “CARB 2” but the resin type as “ULEF” and/or reported maximum emissions that satisfy ULEF requirements. Due to difficulties in distinguishing between CARB 2 and CARB ULEF product lines and the fact that emission levels appeared similar among mills reporting either CARB 2 or CARB ULEF certification standards, these mills were grouped together.

c NAF = No Added Formaldehyde.

Table C-2. Formaldehyde Emissions Standards in the CARB Air Toxic Control Measure for Formaldehyde Emissions from Compressed Wood Productsa (ppm)

Emissions Standard	HWPW	MDF	Particleboard

CARB 1	0.08	0.21	0.18

CARB 2	0.05	0.11b	0.09

CARB ULEF –       less frequent testing	0.05	90% of samples < 0.06

All samples < 0.09c	90% of samples < 0.05

All samples < 0.08

CARB ULEF – exemption from third party certification	90% of samples < 0.04

All samples < 0.05	90% of samples < 0.04

All samples < 0.06	90% of samples < 0.04

All samples < 0.06

CARB NAF	90% of samples < 0.04

All samples < 0.05	90% of samples < 0.04

All samples < 0.06	90% of samples < 0.04

All samples < 0.06

a The Formaldehyde Standards for Composite Wood Products Act (FSCWPA) emission limits are the same as the CARB2 ATCM limits.

b The CARB 2 emission limit for thin MDF is 0.13 ppm.

c The CARB ULEF limits for thin MDF are 90% of samples < 0.08 ppm and all samples < 0.11 ppm.

Among imported products, baseline emission levels were estimated separately for products from Canada versus those from the rest of the world. The known composite wood manufacturers in Canada were compared to the CARB list of certified mills, and most Canadian mills were found to be CARB-certified. As a result, Canadian mills were assumed to achieve the same baseline emissions as U.S. mills (whose emissions are shown above in Table C-1).

The baseline emission levels for non-Canadian imported CWPs were estimated using data from a 2009 presentation by Professional Service Industries, a CARB Third Party Certifier (TPC). Although PSI is located in the U.S., the mills that it certifies are located mainly in Asia. The mills certified by PSI are located in countries that are major sources of pressed wood products imported into the United States; thus, the data from the PSI presentation were assumed to represent emission levels from all non-Canadian CWPs imported into the U.S.

The PSI presentation included histograms of observed formaldehyde emission levels for hardwood plywood, MDF, and particleboard. The data included emission levels for 387, 198, and 193 samples of hardwood plywood, MDF, and particleboard, respectively, and for all three product types combined. After imputing the data underlying these graphs, the average emission values reported in the presentation were successfully replicated. This information was used to estimate the number of samples at different emission levels.

The emission levels reported in the PSI presentation ranged from near zero to levels exceeding the CARB 2 emission standards by a substantial margin. The emission levels observed in these data were from a period after CARB 1 took effect but before CARB 2 did. Because many of the mills that met the CARB 1 standards at the time when samples were taken may subsequently achieve CARB 2 levels, baseline emissions were predicted by assuming that products with emission levels between the CARB 1 and CARB 2 levels in the PSI data would achieve CARB 2 levels by 2013. Emission levels of 0.06 and 0.05 ppm were used for CARB 2 baseline emissions for MDF and particleboard, respectively, because these levels represent the midpoints of the highest emission intervals in the PSI data that meet the CARB 2 limits. None of the intervals in the PSI data for HWPW reflected the CARB 1 emission limits (the CARB 1 limit of 0.08 ppm is spanned by the interval of 0.075 to 0.125 ppm in the PSI data and the CARB 2 limit of 0.05 ppm is spanned by the interval of 0.0375 to 0.075 ppm). Therefore, no adjustments were made to hardwood plywood for the shift from CARB 1 to CARB 2. After making the MDF and PB adjustments, the average emissions by product type were calculated (see Table C-3).

Although a number of samples in the PSI data had emission levels close to zero, it was not possible to determine whether the products qualify for certification as ultra low-emitting formaldehyde (ULEF) or no added formaldehyde (NAF); the PSI presentation did not identify the resin type used for each sample. Also, as indicated in a footnote to C-2 above, NAF and ULEF have emissions requirements that must be met by 90% of the samples from a mill as well a ceiling value that must be met by all samples. This distribution of emissions could not be determined from the PSI presentation; thus, baseline emission levels were not estimated separately for non-Canadian imports of ULEF and NAF products. Such products are included in the baseline emission estimates for the CARB-2 category.

Table C-3 also includes the share of imports for each product type and emissions standard. This share was estimated by assuming that the fraction of samples for each category in the PSI presentation is equivalent to the share of imports for that category across all non-Canadian composite wood products imported into the U.S.

Table C-3. Baseline Emission Levels for Non-Canadian Imported Composite Wood Products, by Product Type and Emissions Standard

Emissions Standard	Hardwood Plywood	MDF	Particleboard

Average Emissions (ppm)

None	0.163	0.502	0.384

CARB 2	0.015	0.047	0.036

Share of Imports

None	26%	11%	38%

CARB 2	74%	89%	62%

The estimates presented above in Table C-3 rely on several critical assumptions that are a source of uncertainty in this analysis, the most important being as follows:

The sample is representative of imported non-Canadian composite wood products.

It is not known whether the sample is representative of products destined for the United States. The destination of these products could be other countries or their country of origin. On the one hand, U.S. end users may be more likely to insist on lower-emitting products. On the other hand, U.S. end users not shipping to California face less stringent formaldehyde emissions standards than many other potential destinations. (Although many end users prefer to handle a single type of product, rather than one product that meets the California requirements and another type for the other 49 states). The fact that the samples were being tested for formaldehyde emissions by a CARB TPC suggests that many of them were produced by mills whose products ultimately end up in the U.S.

The distribution of emission levels will not change for mills that were producing products with emission levels that currently exceed the CARB 1 standards.

If some of these mills decide to obtain CARB 2 certification, it is not known whether these will be the higher or lower emitting mills on average. Some additional mills (aside from those below the CARB 1 limits but above the CARB 2 limits) may subsequently decide to lower their emission levels.

Conversely, the PSI data may under-represent imported products with very high emission levels. Mills making products likely to exceed the CARB levels may not have had their products tested because they intended to sell them in the other 49 states.

The percentage of samples with current emissions below CARB 1 levels is a reasonable estimate of the percentage of mills that will be achieving CARB 2 levels in the baseline scenario:

The PSI presentation was given after CARB 1 was in effect but before CARB 2 was. It is not known whether more overseas producers ultimately will meet the Phase 2 emission limits than initially met the Phase 1 limits.

For the purposes of TSCA Title VI, laminated products are a subset of hardwood plywood. The statute defines a laminated product as one made by affixing a wood veneer to a particleboard, medium-density fiberboard, or veneer-core platform. The statutory definition goes on to state that laminated products are component parts used in the construction or assembly of a finished good, and that a laminated product is produced by the manufacturer or fabricator of the finished good in which the product is incorporated. EPA is given the authority to modify the statutory definition of laminated product through rulemaking. EPA also is directed to use all available and relevant information to determine whether the definition of hardwood plywood should exempt engineered veneer or any laminated product.

Note that baseline emissions data are not available for hardwood plywood defined as laminated products. The CARB 1 standard for hardwood plywood is used to represent the average baseline emission level for laminated products made in the U.S. and Canada. The CARB 1 level represents the average emission level that CARB found prior to promulgating the ATCM. It reflects a mix of products using different resin types, including both UF and NAF resins. This level is considered to be a reasonable proxy for domestically produced laminated products. These products are thought to generally be made with UF or PVA resin, so their emissions may be similar to those from stock hardwood panel products before the ATCM went into effect.

For laminated products made outside the U.S. and Canada, average baseline emissions were assumed to be the same as the levels for imported hardwood plywood that does not meet an emission standard (estimated from the PSI presentation). Emissions data prior to the CARB ATCM are not available for non-Canadian imported hardwood plywood. Because the PSI presentation was given after CARB 1 was in effect, it presumably reflects a reduction in emissions compared to pre-ATCM levels. Therefore, if baseline laminated product emissions are similar to pre-ATCM emissions, using the average of all non-Canadian imported hardwood plywood would underestimate emission levels for laminated products. Using the estimated average emissions from hardwood plywood that does not meet an emissions standard reflects the possibility that many of these imported laminated products are made with UF resins.

Table C-4 lists the emission levels used for the baseline 2013 scenario for CWPs, including laminated products; the values listed reflect the assumptions and choices described above. The estimated share of U.S. consumption also is listed in the table for each product type and associated country of origin.

Table C-4. Baseline Emission Levels for Composite Wood Products by Product Type, Country of Origin, and Emission Standard

Emissions Standard	Hardwood Plywood	MDF	Particleboard	Laminated Products

	U.S./Can.	Non-U.S./Can.	U.S./Can.	Non-U.S./Can.	U.S./Can.	Non-U.S./Can. U.S./Can.	Non-U.S./Can.

Average Emissions (ppm)

None	0.058	0.163	---	0.502	0.058	0.384	0.058	0.163

CARB 1	---	---	---	---	0.090	---	---	---

CARB 2	0.032	0.015	0.082	0.047	0.057	0.036	---	---

CARB ULEF

	0.024

0.042

	CARB NAF	0.013

0.035

0.013

	Share of U.S. Consumption

None	0.1%	16.6%	---	0.8%	0.2%	1.1%	36.0%	64.0%

CARB 1	---	---	---	---	1.7%	---	---	---

CARB 2	19.7%	47.4%	79.2%	7.2%	85.0%	1.9%	---	---

CARB ULEF

	4.2%

3.0%

	CARB NAF	16.2%

8.6%

7.1%

C.2	REDUCED EMISSIONS CLASSES

Seven analytical options were evaluated in the EPA exposure assessment, as listed and described briefly in Table C-5. The first four options – CARB1, CARB2/Statutory Option, CARB2/Statutory Option including laminated products at NAF, and NAF – assume that progressively higher percentages of CWPs meet stricter emission standards. The last three scenarios are similar to CARB1, CARB2/Statutory Option, and NAF, with the single exception that laminated products are not regulated as HWPW under TSCA.

Table C-5. Alternative Analytical Options Evaluated in the Exposure Assessment

Analytical Option	Description

CARB1, Including Laminated Productsa	All CWPs, including laminated productsb, are at emission levels that meet CARB Phase 1 standards1. Products that meet CARB Phase 1 standards at baseline are assumed to remain at that emission level.

CARB2 / Statutory Option, Including Laminated Productsa,c	All CWPs, including laminated products, are at emission levels that meet CARB Phase 2 standards. Products that meet CARB Phase 2 standards at baseline are assumed to remain at that emission level.

CARB2 / Statutory Option, with Laminated Products at NAF	As above, except that laminated products are assumed to meet NAFd standards.

NAF, Including Laminated Productsa	All CWPs, including laminated products, are at emission levels that meet NAF standards. Products that meet NAF standards at baseline are assumed to remain at that emission level.

CARB1, Excluding Laminated Products	Like CARB1 above, except that laminated products are not regulated as HWPW and, thus, are assumed remain at baseline emission levels.

CARB2/Statutory Option,

Excluding Laminated Products	Like CARB2 above, except that laminated products are not regulated as HWPW and, thus, are assumed remain at baseline emission levels.

NAF, Excluding Laminated Products	Like NAF above, except that laminated products are not regulated and, thus, are assumed remain at baseline emission levels.

a Included among the emission classes in FIAM-pwp

b 30% of all HWPW products are assumed to be laminated products.

b The CARB emission standards for this scenario are equivalent to those specified in the FSCWPA.

d NAF = no added formaldehyde.

In the economic analysis presented to the Small Business Advocacy Review (SBAR) Panel for the formaldehyde rule, EPA estimated that HWPW production (excluding engineered wood flooring) was 1,749 thousand square feet (on a 3/8-inch basis) in 2006, and that laminated product production (excluding engineered wood flooring) was about 408 million square feet on a 5/8-inch basis, equivalent to about 680 million square feet on a 3/8-inch basis.  Thus, based on these estimates, laminated products account for about 28% of combined HWPW production. The Hardwood Plywood and Veneer Association has indicated that laminated products represent about 30% of engineered wood flooring production. Therefore, this exposure analysis assumes that laminated products represent 30% of the volume of HWPW.

Table C-6 lists emission levels and market shares for the same set of CWPs under the assumption that CARB1 emission limits would be in effect for all CWPs, including laminated products. In compiling this table, it was first assumed that emission levels of all products meeting CARB1 or stricter (CARB2/ULEF/NAF) standards at baseline would not change. Next, it was assumed that any products listed as not meeting any emission standard at baseline, but whose emission levels would comply with CARB1, also would remain at their baseline emission levels. For example, some U.S.-produced HWPW and PB products are not certified as meeting an emission standard at baseline but nonetheless have emission levels that comply with CARB Phase 1 emission limits; thus, their emission levels are assumed to remain at the baseline level under this scenario/analytical option. As noted in a table footnote, for the CARB1 analytical option laminated products were assumed to be at the same emission levels as HWPW if regulated and at baseline emission levels (see Table C-4) if not regulated.

Table C-6. Emission Levels for CARB1 Analytical Option by CWP Type, Origin, and Emissions Standard

Emissions Standard	Hardwood Plywooda	MDF	Particleboard

	U.S.	Non-U.S.	U.S.	Non-U.S.	U.S.	Non-U.S.

Average “Emissions” (ppm)

None	---	---	---	---	---	---

CARB1 (previously NOT CARB1)	0.058b	0.058	---	0.14c	0.058b	0.090

Already at CARB1	---	---	---	---	0.090	---

CARB2	0.032	0.015	0.082	0.047	0.057	0.036

ULEF	---	---	0.024	---	0.042	---

NAF	0.013	---	0.035	-	0.013	-

Share of U.S. Consumption

None	---	---	---	---	---	---

CARB1 (previously NOT CARB1)	0.1%	16.6%	---	0.8%	0.2%	1.1%

Already at CARB1	---	---	---	---	1.7%	---

CARB2	19.7%	47.4%	79.2%	7.2%	85.0%	1.9%

ULEF	---	---	4.2%	---	3.0%	---

NAF	16.2%	---	8.6%	---	7.1%	---

a For the CARB1 scenario that includes laminated products, those products are assumed to have the same emission levels as hardwood plywood; for the CARB1 scenario that excludes laminated products, those products are assumed to have baseline emission levels as listed in Table C-4.

b Products in these cells have baseline emission levels that comply with CARB1, even though producers reported that they were not intentionally meeting any particular standard. Because the baseline levels already comply with CARB1, the emission levels for these products are assumed not to change and, thus, are the same as listed in Table C-4.

c Products in this cell are not CARB1-compliant at baseline; thus, their emission levels are assumed to change for the CARB1 scenario. The assumed emission level is 67 % of the level that would exactly comply with CARB1; as noted in the text, industry generally sets target emission levels below the standard to ensure that it is being met, given variability across/within production lots as well as measurement uncertainty.

For the CARB1 scenario it was further assumed that products listed as not meeting any emission standard at baseline, and whose emission levels exceed the CARB Phase 1 limit, would attain emission levels equal to those of corresponding U.S. products listed as not meeting any emission standard but nonetheless complying with CARB1 at baseline. For example, non-U.S. HWPW not complying with CARB1 at baseline, with an average emission level of 0.163 ppm, was assumed to match the level (0.058 ppm) of U.S.-produced HWPW complying with CARB1 at baseline, and its market share (16.6%) was shifted from “None” to “CARB1” in the table.

Lastly, it was assumed that products not meeting any emission standard at baseline, and for which there are no comparable products complying with CARB1 at baseline, would obtain an emission level equal to 67% of the CARB1 limit – the CWP industry generally sets targets for emission levels below the standard to ensure that it is being met, considering the variability across/within production lots as well as measurement uncertainty. For example, non-U.S. MDF, with an emission level at baseline (0.502 ppm) that is not CARB1-compliant, was assumed to change to a level equal to 67 percent of the CARB1 standard (0.67 x 0.21 ppm = 0.14 ppm).

Table C-7 lists emission levels and market shares for the analytical option where CARB2/TSCA Title VI statutory emission limits would be in effect. As with the CARB1 scenario, it was assumed that emission levels of all products already meeting CARB2 or stricter standards (ULEF/NAF) would not change. Next, it was assumed that products not meeting CARB2 at baseline (including those meeting the less strict CARB1 standard) would obtain emission levels equal to U.S. products of the same CWP type that comply with CARB2 at baseline. For example, both U.S.-produced HWPW (baseline level of 0.058 ppm) and non-U.S. HWPW (baseline level of 0.163 ppm) were assumed to shift to a CARB2-compliant emission level of 0.032 ppm. For this analytical option, laminated products were assumed to be at the same emission levels as HWPW if regulated and at baseline emission levels (see Table C-4) if not regulated.

Table C-7. Emission Levels for CARB2 Analytical Option by CWP Type, Origin, and Emissions Standard

Emissions Standard	Hardwood Plywooda	MDF	Particleboard

	U.S.	Non-U.S.	U.S.	Non-U.S.	U.S.	Non-U.S.

Average “Emissions” (ppm)

None	---	---	---	---	---	---

CARB1	---	---	---	---	---	---

CARB2 (previously NOT CARB2)	0.032	0.032	-	0.082	0.057	0.057

Already at CARB2	0.032	0.015	0.082	0.047	0.057	0.036

CARB2	---	---	0.024	---	0.042	---

ULEF	0.013	---	0.035	---	0.013	---

NAF	---	---	---	---	---	---

Share of U.S. Consumption

None	---	---	---	---	---	---

CARB1	---	---	---	---	---	---

CARB2 (previously NOT CARB2)	0.1%	16.6%	---	0.8%	1.9%	1.1%

Already at CARB2	19.7%	47.4%	79.2%	7.2%	85.0%	1.9%

CARB2	---	---	4.2%	---	3.0%	---

ULEF	16.2%	---	8.6%	---	7.1%	---

NAF	---	---	---	---	---	---

a For the CARB2 scenario that includes laminated products, those products are assumed to have the same emission levels as hardwood plywood; for the CARB2 scenario that excludes laminated products, those products are assumed to have baseline emission levels as listed in C-4.

Table C-8 lists emission levels and estimated percentages under the analytical option whereby NAF emission limits would be in effect. First, it was assumed that emission levels of all products meeting the NAF standard at baseline would not change. Next, it was assumed that products not meeting NAF at baseline (including those meeting less strict standards) would attain the emission levels for U.S. products of the same CWP type that are NAF-certified at baseline. For example, U.S.-produced HWPW accounts for 36 percent of all HWPW production. A subset of the U.S. HWPW production, accounting for 19.8 percent, does not comply with NAF at baseline but attains a NAF-compliant emission level of 0.013 ppm under the NAF analytical option; the remaining 16.2 percent, already NAF-compliant, likewise has an emission level of 0.013 ppm. Lastly, it was assumed that MDF products meeting ULEF at baseline, but with average emission levels lower than those for NAF-compliant MDF products at baseline, would not change. As with the analytical options described above (CARB1 and CARB2), for the NAF analytical option laminated products were assumed to be at the same emission levels as HWPW meeting the NAF standard if regulated and at baseline emission levels (see Table C-4) if not regulated.

Table C-8. Emission Levels for NAF Scenario by CWP Type, Origin, and Emissions Standard

Emissions Standard	Hardwood Plywooda	MDF	Particleboard

	U.S.	Non-U.S.	U.S.	Non-U.S.	U.S.	Non-U.S.

Average “Emissions” (ppm)

None	---	---	---	---	---	---

CARB P1	---	---	---	---	---	---

CARB P2	---	---	---	---	---	-

NAF (previously not NAF with non-NAF emissions)	0.013	0.013	0.035	0.035 0.013	0.013

NAF (previously not NAF with NAF emissions)	---	---	0.024	---	---	---

Already at NAF	0.013	---	0.035	---	0.013	---

Share of U.S. Consumption

None	---	---	---	---	---	---

CARB P1	---	---	---	---	---	---

CARB P2	---	---	---	---	---	---

NAF (previously not NAF with non-NAF emissions)	19.8%	64.0%	79.2%	8.0% 89.9%	3%

NAF (previously not NAF with NAF emissions)	---	---	4.2%	---	---	---

Already at NAF	16.2%	---	8.6%	---	7.1%	---

a For the NAF scenario that includes laminated products, those products are assumed to have the same emission levels as hardwood plywood; for the NAF scenario that excludes laminated products, those products are assumed to have baseline emission levels as listed in Table C-4.

Table C-9 lists emission levels and market shares under the analytical option whereby CARB2 emission limits would be in effect, but with the added assumption that all laminated products (assumed to account for 30 percent of all HWPW production) are NAF-compliant (e.g., using NAF cores laminated with NAF resins) at an emission level of 0.013 ppm. Note that the estimated percentages for the U.S. and non-U.S. HWPW columns have been adjusted in the table such that all HWPW production, including laminates, sums to 100 percent.

Table C-9. Emission Levels for CARB2 Scenario with Laminates at NAF by CWP Type, Origin, and Emissions Standard

Emissions Standard	Hardwood Plywood	MDF	Particleboard	Laminated Productsa

	U.S.	Non-U.S.	U.S.	Non-U.S.	U.S.	Non-U.S.	U.S.	Non-U.S.

Average “Emissions” (ppm)

None	---	---	---	---	---	---	---	---

CARB1	---	---	---	---	---	---	---	---

CARB2 (previously NOT CARB2)	0.032	0.032	---	0.082	0.057	0.057	---	---

Already at CARB2	0.032	0.015	0.082	0.047	0.057	0.036	---	---

CARB2	---	---	0.024	---	0.042	---	---	---

ULEF	0.013	---	0.035	---	0.013	---	---	---

NAF	---	---	---	---	---	---	0.013	0.013

Share of U.S. Consumption

None	---	---	---	---	---	---	---	---

CARB1	---	---	---	---	---	---	---	---

CARB2 (previously NOT CARB2)	0.1%	11.6%	---	0.8%	1.9%	1.1%	---	---

Already at CARB2	13.8%	33.2%	79.2%	7.2%	85.0%	1.9%	---	---

CARB2	---	---	4.2%	---	3.0%	---	---	---

ULEF	11.3%	---	8.6%	---	7.1%	---	---	---

NAF	---	---	---	---	---	---	10.8%	19.2%

	a Assumed to account for 30% of all HWPW production.

C.3	SLOPES AND INTERCEPTS FOR EMISSION RATES

Appendix D lists emission rates for various types of PWPs that were derived from sets of chamber emission tests conducted during the 1980s and up through the mid-1990s. A distinguishing feature of these chamber tests, although somewhat dated, is that they were conducted at multiple air exchange rates and/or product loading ratios, enabling estimation of model parameters – slope and intercept – that reflect the dependence of the emission rate on the indoor formaldehyde concentration. The slope is a mass transfer coefficient that reflects the “backpressure” effect of the indoor formaldehyde concentration on the emission rate, whereas the intercept reflects the hypothetical emission rate when the indoor formaldehyde concentration is zero.

The following equation, identical to Eqn. 3-4 in Section 3.2 of the main document, was used as a basis for determining the intercept (b) associated with products meeting certain emission standards:

[CH2O]SS = [CH2O]out + (CH2OER( * Area)/Q	(Eqn. C-1)

where:

[CH2O]SS	=	steady-state formaldehyde concentration inside the compartment (mg/m3)

[CH2O]out	=	steady-state formaldehyde concentration outside the compartment (mg/m3)

CH2OER’	=	the emission rate of a solid formaldehyde source inside the compartment (mg/h)

Area	=	the surface area of the formaldehyde source (m2)

Q	=	airflow rate into and out of the compartment (m3/hr)

The emission rate of a solid source is:

CH2OER( = -m * [CH2O]V + b		(Eqn. C-2)

where:

m	=	the mass transfer coefficient (m/hr)

[CH2O]V	=	the CH2O concentration in the vapor phase (mg/m3)

b	=	a constant; the emission rate at zero CH2O concentration in the air (mg/m2-hr).

Assuming that [CH2O]out is zero and that [CH2O]V  = [CH2O]SS , and substituting Eqn. C-2 into Eqn. C-1, we can solve for b as follows:

	b = [CH2O]SS * (1 + m * Area / Q) * (Q / Area)	(Eqn. C-3)

ASTM E 1333, Standard Test Method for Determining Formaldehyde Concentrations in Air and Emission Rates from Wood Products Using a Large Chamber, is a commonly used method for demonstrating compliance with formaldehyde emission standards. The method prescribes an air exchange rate for testing of 0.5 hr-1 (i.e., 0.5 ACH) and product loading ratios of 0.43 m2/m3for PB, 0.95 m2/m3for HWPW, and 0.26 m2/m3for MDF. Using these rates along with an assumed slope (m) for a given PWP type, the corresponding intercept can be determined for a hypothetical source that just meets a given emissions standard.

For example, the CARB2 emission standard for MDF is 0.11 ppm or 0.135 mg/m3. An arbitrary chamber volume of 100 m3, together with a value of 50 m3/hr for Q (corresponding to an air exchange rate of 0.5/hr), was used in the calculation. The volume assumed does not matter, as the exposed surface area scales to the volume via the loading ratio – with a volume of 100 m3 the corresponding surface area is 26 m2. A slope of 1.06 m/hr was assumed; this value is the average slope from about 30 tests of different MDF specimens, as listed in Appendix D.

Substituting the assumed values given above in Eqn. 4-2, the intercept (b) that corresponds to the CARB2 emission standard for MDF is calculated as follows:

b = 0.135 mg/m3 * (1 + 1.06 m/hr * 26m2 / 50 m3) * (50 m3 / 26 m2)

= 0.40 mg/m2-hr

Table C-10 lists the calculated intercepts associated with various emission levels for HWPW, MDF and PB, as listed previously in Tables C-6 through C-9, using the calculation method described above and an assumed slope for each CWP type as indicated in the table.

Table C-10. Calculated Intercepts for Various Emission Levels for Each CWP Type

Emission Standard –  Origin	Emission Levela	Assumed Slope	Calculated Intercept

	ppm	mg/m3	m/hr	mg/m2/hr

Hardwood Plywood

None – U.S.	0.058	0.072	0.27	0.057

None – non-U.S.	0.163	0.201	0.27	0.160

CARB1 – U.S. & non-U.S.	0.058	0.072	0.27	0.057

CARB2 – U.S.	0.032	0.040	0.27	0.031

CARB2 – non-U.S.	0.015	0.019	0.27	0.019

NAF – U.S.	0.013	0.016	0.27	0.013

Medium Density Fiberboard

None – U.S.	---	---	1.06	---

None – non-U.S.	0.502	0.620	1.06	1.849

CARB1 – U.S.	0.140	0.173	1.06	0.516

CARB2 – U.S.	0.082	0.101	1.06	0.302

CARB2 – non-U.S.	0.047	0.058	1.06	0.173

ULEF – U.S.	0.024	0.030	1.06	0.088

NAF – U.S.	0.035	0.043	1.06	0.129

Particleboard

None – U.S.	0.058	0.072	0.7	0.133

None – non-U.S.	0.384	0.474	0.7	0.883

CARB1 – U.S. 	0.058	0.072	0.7	0.133

CARB1 – non-U.S.	0.090	0.111	0.7	0.207

CARB2 – U.S.	0.057	0.070	0.7	0.131

CARB2 – non-U.S.	0.036	0.044	0.7	0.083

NAF – U.S. & non-U.S.	0.013	0.016	0.7	0.030

a mg/m3 formaldehyde = ppm formaldehyde * 1.23

Providing standard-specific slopes and intercepts for each CWP type would prove cumbersome, exceeding the number of input rows available for sources in the FIAM model. It was determined experimentally that using a composite intercept together with the corresponding total exposed surface area for a given CWP type yielded identical modeling results to that from the more tedious approach of using values for the individual components meeting different emission standards. The composite intercept was calculated as a weighted average of the individual intercepts, using the market share as the weight; the resultant composite intercepts are shown for the baseline scenario in Table C-11 for each CWP type, along with standard-specific intercepts.

Table C-11. Composite Intercepts by CWP Type – Baseline Scenario

Emission Standard – Origin	Slope	Intercept	Market Share

Hardwood Plywood

None – U.S.	0.27	0.057	0.1%

None – non-U.S.	0.27	0.160	16.6%

CARB2 – U.S.	0.27	0.031	19.7%

CARB2 –  non-U.S.	0.27	0.015	47.4%

NAF – U.S.	0.27	0.013	16.2%

Composite	0.27	0.042	100 %

Medium Density Fiberboard

None – non-U.S.	1.06	1.849	0.8%

CARB2 – U.S.	1.06	0.302	79.2%

CARB2 non-US	1.06	0.173	7.2%

ULEF – U.S.	1.06	0.088	4.2%

NAF – U.S.	1.06	0.129	8.6%

Composite	1.06	0.281	100 %

Particleboard

None – U.S.	0.70	0.133	0.2%

None – non-U.S.	0.70	0.883	1.1%

CARB1 – U.S.	0.70	0.207	1.7%

CARB2 – U.S.	0.70	0.131	85.0%

CARB2 –  non-U.S.	0.70	0.083	1.9%

ULEF – U.S.	0.70	0.097	3.0%

NAF – U.S.	0.70	0.030	7.1%

Composite	0.70	0.131	100 %

Composite intercepts for baseline and other emission scenarios – CARB1, CARB2 and NAF – are shown by CWP type in Table C-12, without the underlying details. The most notable difference across scenarios is that the NAF intercepts are substantially lower than for the other three scenarios, for each CWP type.

Table C-12. Composite Intercepts by CWP Type and Emissions Scenario

CWP Type	Composite Intercept

	Baseline	CARB1	CARB2	NAF

Hardwood Plywood	0.042	0.025	0.021	0.013

Medium Density Fiberboard	0.281	0.271	0.269	0.127

Particleboard	0.131	0.124	0.122	0.030

The modeling also accounted for some PWP types that would not be subject to emission standards because they are specifically exempt from TSCA Title VI. Underlayment in homes typically is either tongue-and-groove softwood plywood (SWPW) or oriented strand board (OSB). The emission rates from earlier chamber tests on SWPW are thought to be applicable to either type; for example, a study by Hodgson et al. reported virtually the same intercept (0.029) for OSB as did the earlier tests for SWPW (0.030).

Interior doors were represented using estimated emission rates from chamber testing of 6-panel white doors that were used in the EPA pilot study; this is the only known study in which such doors have been tested at multiple air exchange/loading rates, enabling calculation of both a slope and an intercept. The emission rates for these doors also were used to represent those for coated (but not laminated) CWP materials, assuming a similar barrier effect.

Because the interiors of such coated materials presumably would be in compliance with any rules governing CWP emissions, the intercept for interior doors and coated CWPs was varied across emission scenarios. It was observed that, at baseline, the intercept for these products was close to halfway between the intercepts for HWPW and PB. Thus, the average of those two intercepts for other emission scenarios – CARB1, CARB2 and NAF – was used for doors and coated CWPs; the average intercepts were 0.074 for CARB1, 0.071 for CARB2, and 0.0215 for NAF.  Emission factors for underlayment, interior doors, and coated CWPs are listed in Table C-13.

Table C-13. Emission Rates for Underlayment and Coated CWPs – Baseline Scenario

PWP Type/Class	Proxy Used for Emission Rate 	Slope	Intercept

Underlayment (OSB)	Softwood Plywood

(PF Resin)	0.61	0.030

Interior Doors & Coated CWPsa	6-panel Doors Used

 in EPA Pilot Study 	0.52	0.082

a CWPs could be coated, for example, with primer/paint, vinyl film, or thermally fused paper.

Appendix D

Historical Testing of PWPs to Derive Slope and Intercept Values

D.1	BACKGROUND

During the 1980s and up through the mid-1990s, a number of organizations conducted sets of chamber emission tests at multiple air exchange rates and/or product loading ratios, enabling the estimation of model parameters – slope and intercept – that reflect the dependence of the emission rate on the indoor formaldehyde concentration. The following source types were tested:

Particleboard underlayment

Mobile home decking

Industrial particleboard

Medium density fiberboard

Hardwood plywood paneling (with a print face)

Hardwood plywood paneling (with a paper face)

Hardwood plywood paneling (with a wood veneer face)

Hardwood plywood paneling (unspecified face material)

Softwood plywood (phenol-formaldehyde resin)

Hardboard (phenol-formaldehyde resin)

Kitchen cabinets

Interior doors.

D.2	DETAILED CHAMBER TESTING RESULTS

Table D-1 lists, by product type, products for which multiple chamber tests were conducted in the 1980s-1990s to enable estimation of emission rate model parameters (slope and intercept). The table also provides references for the data and additional information, as available, on chamber testing conditions (air exchange rate and loading ratio). The R2 values listed in the right-hand column of the table, which indicate the degree of correspondence between calculated and predicted emission rates, are based on regression analysis of calculated emission rates against measured chamber concentrations for the various products tested, from which the slope and intercept were estimated (see Section D.4 for an example of this type of analysis). Not all investigators reported these values; values are listed in cases where they were reported.

The abbreviated names assigned to individual available sources in the table reflect the organization (e.g., EPA, ORNL) or individual that performed the testing from which modeling parameters were estimated. Several Available Sources – EPA-PBU for Particleboard Underlayment, EPA-HWP for Hardwood Plywood Paneling (Unspecified), EPA-CABINET for Kitchen Cabinets, and EPA-DOOR for Interior Doors – are based on chamber testing performed as part of the EPA pilot study on formaldehyde (see Appendix A).

	Table D-1.  Calculated Slopes and Intercepts for Matthews Model from Chamber Tests Conducted at 23 (C, 50 % RH or at 25 (C, 50 % RHa

	(Listed Cases are for Conditions of 23 (C and 50 % RH)

Product Type

Product Codeb

No. of Data Pointsc

N/L Ranged

Measured Concentration Range (ppm)

Matthew’s Emission Modele

ER = -m (conc) + b

Slope (m/hr)

Intcpt. (mg/m2/hr)

R2 Valuef

Particleboard Underlayment

ORNL-PCB #1

ORNL-PCB #2

ORNL-PCB #3

ORNL-PBU 1 #4

ORNL-PBU 3 #3

ORNL-PBU 3 #6

GP-2

GP-4

GP-5

NBS-USM2-2B

NBS-USM2-3B

NBS-USM5-1A

NBS-U-5,8,9,12,18

EPA-PBU

3

4

4

4

4

3

0.13 to 0.63

0.32 to 5.70

0.10 to 0.95

0.16 to 9.18

0.44 to 6.67

0.60 to 2.37

0.077 to 0.162

0.057 to 0.354

0.084 to 0.158

0.084 to 0.215

0.058 to 0.442

0.062 to 0.118

0.32

0.70

0.88

1.72

0.70

0.93

0.84

1.57

0.76

0.36

0.38

0.62

0.60

1.25

0.09

0.44

0.19

0.46

0.51

0.47

0.40

0.37

0.58

0.18

0.27

0.33

0.18

0.28

0.92

0.98

0.92

0.77

0.96

0.52

0.81

0.98

0.42

0.76

Mobile Home Decking

LEH-B

GP-MHD

1.35

0.77

0.66

0.39

Industrial Particleboard

ORNL-PBI 3#2

LEH-C

LEH-D

LEH-H

LEH-I

LEH-J

LEH-K

LEH-L

LEH-M

LEH-N

LEH-O

LEH-P

LEH-Q

4

8

9

6

6

6

6

6

6

6

6

6

6

0.32 to 3.31

0.76 to 6.10

0.31 to 6.10

0.59 to 3.82

0.59 to 3.82

0.59 to 3.82

0.59 to 3.82

0.59 to 3.82

0.59 to 3.82

0.59 to 3.82

0.59 to 3.82

0.59 to 3.82

0.59 to 3.82

0.096 to 0.457

0.47

1.00

0.54

1.02

0.87

1.30

0.96

1.07

0.40

1.32

0.58

1.58

0.98

0.42

1.24

0.36

0.45

0.60

0.27

0.32

0.53

0.14

0.24

0.22

0.37

0.39

0.88

Industrial Particleboard (continued)

GP-1A

GP-3A

GP-6A

GP-7A

GP-8A

GP-9A

GP-11A

NBS-USM7-1B

NBS-USM2-1A

NBS-USM6-1B

NBS-USM6-2A

NBS-USM6-3B

NBS-USM4-1B

GP-1N

GP-2N

GP-3N

GP-4N

GP-5N

GP-6N

GP-7N

0.41

0.63

0.46

0.38

0.63

0.62

0.55

0.45

0.39

0.80

0.33

0.64

0.28

0.70

0.72

0.81

0.55

0.50

0.46

0.58

0.12

0.33

0.34

0.24

0.33

0.35

0.29

0.12

0.30

0.18

0.18

0.29

0.20

0.53

0.53

0.35

0.27

0.37

0.34

0.48

0.98

0.67

0.98

0.32

0.94

0.98

Medium Density Fiberboard

ORNL-MDF 1 #5

ORNL-MDF 3 #5

ORNL-MDF 1 #4

ORNL-MDF 2 #4

ORNL-MDF-U

LEH-E

LEH-F

LEH-G

GP-1

GP-2

GP-3

GP-4

GP-5

GP-6

4

4

9

9

15

1.47 to 12.5

1.33 to 12.5

0.31 to 6.10

0.31 to 6.10

0.15 to 7.09

0.170 to 0.952

0.160 to 0.936

0.89

1.00

1.25

1.58

0.91

0.48

0.80

0.80

4.98

1.17

2.00

2.22

3.87

0.78

2.78

2.49

1.62

1.09

4.24

0.32

0.79

0.83

1.27

0.77

0.84

1.33

0.80

0.50

0.98

0.81

Medium Density Fiberboard (continued)

GP-7

GP-8

GP-9

GP-10

GP-11

GP-12

GP-13

GP-14

GP-15

NBS-LMDF-1C

NBS-LMDF-2B

NBS-MDF 1

NBS-MDF 2

NBS-MDF 3

NBS-MDF 4

NBS-MDF 5

0.73

0.43

0.69

1.83

0.81

1.45

0.90

1.30

0.77

0.88

0.71

1.50

1.16

1.09

0.76

0.65

0.58

0.46

0.32

0.92

0.58

1.31

0.63

0.75

0.39

0.64

0.73

1.73

1.14

1.31

1.29

1.43

Hardwood Plywood Paneling (Print)

ORNL-PNPR 2 #3

ORNL-PNPR 3 #3

ORNL-PNPR 2 #5

ORNL-PNPR 3 #1

ORNL-PAN #2

4

4

4

0.31 to 6.57

0.44 to 3.34

0.32 to 1.90

0.085 to 0.719

0.029 to 0.127

0.021 to 0.055

0.46

0.37

0.40

0.85

0.48

0.67

0.13

0.25

0.26

0.05

0.86

0.94

0.77

Hardwood Plywood Paneling (Paper)

ORNL-PNP 2 #4

ORNL-PNP 3 #1,2g

ORNL-PNP 3 #1,2h

4

4

3

0.31 to 6.57

0.20 to 1.11

0.17 to 1.11

0.037 to 0.426

0.063 to 0.225

0.129 to 0.402

0.27

0.10

0.27

0.27

0.09

0.22

0.61

0.69

0.98

Hardwood Plywood Paneling (Veneer)

ORNL-PND 1 #1,2g

ORNL-PND 1 #1,2h

ORNL-PND 3 #5

ORNL-PAN #1

4

4

3

4

0.15 to 0.35

0.12 to 1.06

0.32 to 1.11

0.14 to 0.95

0.105 to 0.194

0.055 to 0.248

0.062 to 0.137

0.072 to 0.162

0.19

0.11

0.34

0.45

0.08

0.08

0.11

0.13

0.36

0.81

0.90

0.85

Hardwood Plywood Paneling (Unknown)

NBS-P6-1

NBS-P8-1

NBS-P10-1

NBS-P14-1

NBS-P17-1

NBS-P21-1

EPA-HWP

8

5

11

8

5

0.04 to 1.91

0.03 to 1.14

0.04 to 4.86

0.18 to 5.20

0.08 to 7.36

0.26 to 1.04

0.022 to 0.253

0.027 to 0.239

0.045 to 0.370

0.014 to 0.098

0.020 to 0.224

0.066 to 0.106

0.12

0.12

0.45

0.67

0.52

0.22

0.96

0.05

0.04

0.30

0.08

0.15

0.03

0.16

0.83

0.96

0.71

0.66

0.72

0.18

0.98

Softwood Plywood

(PF Resin)

ORNL-PFPLY #1

5

0.23 to 1.05

0.017 to 0.029

0.61

0.03

--

Hardboard

(e.g., "Masonite")

ORNL-HBD 1

7

--

0.02 to 0.095

1.39

0.17

0.98

Kitchen Cabinets

EPA-CABIN

3

0.39 to 2.29

0.023 to 0.075

0.49

0.08

0.94

Interior Doors

EPA-DOOR

3

0.58 to 2.44

0.022 to 0.061

0.52

0.08

0.86

a	The data listed in this table are based on the results of emission rate tests performed at Oak Ridge National Laboratory (ORNL) for the Consumer Product Safety Commission (CPSC), at the National Bureau of Standards (NBS) for EPA and CPSC, at Georgia Pacific Corp. (GP), and at Weyerhauser Co. by Dr. W. F. Lehmann. The data listed in the table for individual sources were obtained from or are based on the results reported in Progress Reports No. I, II, XIV, XV, XVI, and XVIII submitted to CPSC by ORNL; NBS Report #NBSIR 85-3255 to CPSC; a 1987 NBS report to EPA (Grot et al. 1987); comments submitted by Georgia Pacific Corp. to EPA (Howlett 1988); Lehmann (1987) (also personal communication between B. Lehmann  of Weyerhauser Co. and G. Schweer of EPA on June 30, 1987); and Koontz et al. 1996.

The ORNL reports listed the Matthew’s model parameters for the individual sources and presented summary test data for the tested N/L conditions. The Matthews model parameters listed in the table are as listed in the ORNL reports. Lehmann (1987) and Howlett (1988) reported HBF model parameters for the tested boards; Matthews model parameters for these products were calculated from the HBF model parameters. The NBS report listed Matthews model parameters.

b	Product codes are reported as listed in the ORNL Progress Reports (except for interior plywood, hardboard, and MDF-U) for the ORNL products. The products reported in Lehmann (1987) are denoted by "LEH" followed by the letter code used in his report. The products reported in the NBS reports are denoted by "NBS" followed by the code used in the reports. The products tested by Georgia Pacific Corp. are denoted by "GP" followed by a digit representing the order presented in the report’s tables. The products tested for the EPA Pilot Study (Koontz et al. 1996) are denoted by "EPA."

c	Refers to the number of distinct N/L experiments conducted.

d	N/L is the ratio of the experimental air exchange rate (N), in air changes per hour, to the product loading in the chamber (L), in m2 of product surface area per m3 of chamber volume.

e	ER is the emission rate of the product in units of mg of formaldehyde per m2 of product surface area per hour; the intercept has the same units. The slope units are m/hr.

f	Indicator of the degree of correspondence between calculated emission rates and rates predicted by the regression equation.

g	Only decorative side exposed.

h	Both sides exposed.

REFERENCES CITED IN TABLE D-1:

ANSI 1999. American National Standard: Particleboard. ANSI 208.1-1999, approved February 8, 1999.

ANSI 2002. American National Standard: Particleboard. ANSI 208.2-2002, approved May 13, 2002.

R.A Grot, S. Silberstein, and K. Ishiguro. 1985. Validation of Models for Predicting Formaldehyde Concentrations in Residences Due to Pressed Wood Products. U.S. Dept. of Commerce, National Bureau of Standards. Report #NBSIR 85-3255.

R.A. Grot, S. Nabinger, and S. Silberstein. 1987. Formaldehyde from Low-emitting Pressed Wood Products and the Effectiveness of Various Remedial Measures for Reducing Formaldehyde Emissions. U.S. Dept. of Commerce, National Bureau of Standards.

C.T. Howlett. 1988. Data provided to EPA on January 14, 1988, and on June 6, 1988 by C.T. Howlett (Georgia Pacific Corp.).

M.D. Koontz, H.E. Rector, D.R. Cade, C.R. Wilkes, and L.L. Niang. 1996. Residential Indoor Air Formaldehyde Testing Program: Pilot Study. Report No. IE-2814, prepared by GEOMET Technologies, Inc. for the U.S. Environmental Protection Agency, Washington, DC, under EPA Contract No. 68-D3-0013.

W.F. Lehmann. 1987. Effect of Ventilation and Loading Rates in Large Chamber Testing of Formaldehyde Emissions from Composite Panels. Forest Products Journal 37(4):31-37.

D.3	AVERAGE VALUES FOR SLOPES AND INTERCEPTS

Average slope and intercept values were determined from the data displayed in Table D-1. All data shown in the table were used for each of the product types summarized in Table D-2, except three cases for MDF that were deemed outliers because they had either a substantially higher slope (Product Codes GP-1 and GP-5) or a substantially higher intercept (Product Code ORNL-MDF-U) than other cases within that product group. Although, as noted previously, the data on which these averages are based are somewhat dated, the slopes in the table are useful for estimating hypothetical intercept values for products assumed to meet certain emission standards. Illustrative calculations in this regard are provided in Appendix C (see Section C.1) and in Section 2.3.3 of the main document.

Table D-2.  Calculated Average Slopes and Intercepts for Eight Product Types

Product Type	Average Slope	Average Intercept

Particleboard Underlayment	0.83	0.34

Mobile Home Decking	1.06	0.53

Industrial Particleboard	0.70	0.35

Medium Density Fiberboarda	1.06	1.02

Hardwood Plywood Paneling (Print	0.51	0.27

Hardwood Plywood Paneling (Paper)	0.21	0.19

Hardwood Plywood Paneling (Veneer)	0.27	0.10

Hardwood Plywood Paneling (Unknown)	0.44	0.12

a Two outliers excluded from the calculation; see text.

D.4	ILLUSTRATIVE REGRESSION ANALYSIS ON CHAMBER DATA SET

The data set for this example originated from the EPA pilot study described in Appendix A. Among the product types subjected to chamber testing was a kitchen cabinet ensemble. Test conditions and results for kitchen cabinets prior to the first house loading are shown in Table D-3. The chamber tests were conducted at three air exchange rates – 0.17 ACH, 0.51 CH, and 1.0 ACH – to provide a basis for estimating the relationship between formaldehyde concentration and emission rate. The chamber tests were conducted at a target temperature of 77 °F (25 °C) and a target relative humidity (RH) of 50 percent. The measured “steady-state” chamber concentrations shown in the table are based on adjustment to standard conditions of 77 °F and 50 % RH, per ASTM Standard E-1333. The chamber volume was 1080 ft3 (30.6 m3) and the product loading ratio was 0.13 ft2/ft3 (0.43 m2/m3).

Table D-3.  Chamber Conditions and Test Results for Kitchen Cabinets – EPA Pilot Study

Air Exchange Rate, ACH	Temperature, °F	RH,

%	Chamber Concentration, mg/m3	Calculated Emission Rate, mg/m2-hr

1.00	75.0	50	0.0353	0.0821

0.51	77.5	48	0.0645	0.0765

0.17	77.5	51	0.1143	0.0452