i



## Formaldehyde Indoor Air Model **– Pressed Wood Products,** 

**Version 2.0 (** **FIAM**

**- pwp**  **v2.0) :**  **Model User Manual**  **and Documentation** 

**Exposure Assess ment Branch**  **Economics, Exposure and Technology Division Office of Pollution Prevention and Toxics**  **Office of Chemica l Safety and Pollution Prevention**  **U.S. Environmental Protection Agency 1200 Pennsylvania Avenue, N. W.**  **Washington , D.C. 20460**  **July 2012**ii 

### ACKNOWLEDGMENT EPA acknowledges the analytical and draft preparation support of Versar, Inc. of Springfield, Virginia in the preparation of this report, provided under Contract No. EP - W - 10 - 005.



### Notice This is not an official guidance document and should not be relied upon to determine applicable regulatory

requirements. This document was prepared to provide exposure information for the rulemaking process, and to meet various administrative and legislative requirements. Due to the nature of the information available to EPA, the document contains various assumptions that may not reflect the regulatory determinations that an individual firm or organization would make were it to apply the rule's requirements to its specific circumstanc es. Persons seeking information on specific regulatory requirements should consult 40 CFR Part 767, and the preamble for the regulatory action. Mention of the names of specific companies, organizations, or entities does not constitute an endorsement by

EPA.i 

### TABLE OF CONTENTS **1. INTRODUCTION**  **................................ ................................**  **................................ ....................**  **1 2.**  **USER INT ERFACE**  **................................ ................................**  **................................ .................**  **3** 2.1 Background

– Model Versions ................................ ................................ ................................ 3 2.2 House Screen ................................ ................................ ................................ ........................... 4 2. 2.1 Inputs and Options ................................ ................................ ................................ .... 4 2.2.2 Basis for Defaults ................................ ................................ ................................ ...... 8 2.3 Source Screen ................................ ................................ ................................ ........................ 14 2.3.1 Ty pes of Inputs ................................ ................................ ................................ ....... 14 2.3.2 Adding Default Inputs ................................ ................................ ............................. 15 2.3.3 Adding Custom Inputs ................................ ................................ ............................ 16 2.3.3 Basis for Defaults ................................ ................................ ................................ .... 16 2.4 Exposure Screen ................................ ................................ ................................ .................... 21 2.4.1 Inputs and Options for Age of Sourc es and Formaldehyde Level of Interest ........ 21 2.4.2 Inputs and Options for Exposure Groups ................................ ................................ 22 2.4.3 Inputs and Options for Concentrations Outside the Home ................................ ..... 23 2.4.4 Basis for Defaults ................................ ................................ ................................ .... 24 2.5 Result Screen ................................ ................................ ................................ ......................... 27 2.5.1 Concentration Results ................................ ................................ ............................. 27 2.5.2 Exposure Results ................................ ................................ ................................ ..... 28 2.5.3 Printing Inputs and Results ................................ ................................ ..................... 28 2.5.4 Archiving Inputs and Results for a Run ................................ ................................ .. 28 2.6 Model Access and Additional Features ................................ ................................ ................. 29 2.6.1 Accessing the IGEMS Website ................................ ................................ ............... 29 2.6.2 Saving Inputs for Later Access ................................ ................................ ............... 29 2.6.3 Context- sensitive Help ................................ ................................ ............................ 29 2.7 Example Applications ................................ ................................ ................................ ........... 29 2.7.1 Example 1

– Modeling with Model Default Values ................................ ............... 29 2.7.2 Example 2

– Modeling a Hy pothetical Chamber Test for CARB Compliance ...... 30 2.7.3 Example 3

– Demonstrating an Equilibrium Concentration ................................ ... 31 2.7.4 Example 4

– Examining the Incremental Contribution of a Product ...................... 32 2.7.5 Example 5

– Varying the Decay Rate (Half Life) ................................ .................. 33 **3. MODEL CALCULATIONS AND ASSUMPTIONS**  **................................ ..........................**  **35** 3.1 Generalized Mass - Balance Equation ................................ ................................ ..................... 36 3.2 Steady- S tate Model for Initial Formaldehyde Concentration in One Compartment ............. 37 3.3 Extension of the Steady- State Model to Two Compartments ................................ ............... 39 3.4 Matthews Model Compared to HBF Model ................................ ................................ .......... 40 3.5 Other Potentially

Useful Modeling Constructs ................................ ................................ ..... 42 3.6 Discussion of Indoor Sinks ................................ ................................ ................................ .... 45 3.7 Decay

of Indoor Concentrations ................................ ................................ ............................ 45 3.8 Default Value for Half Life ................................ ................................ ................................ ... 48 3.9 Temperature and Humidity Adjustments ................................ ................................ .............. 51 3.10 Exposure Calculations ................................ ................................ ................................ ........... 53ii

**4. EVALUATION OF MODEL ALGORITH** **MS AND PREDICTIONS ............................**  **55** 4.1 Mathematical Correctness of Model Algorithms ................................ ................................ .. 55 4.2 NI ST Assessment of Matthews Model Predictions ................................ ............................... 55 4.3 Assessment of FIAM - pwp Predictions

– EPA Pilot Study ................................ .................... 56 4.3.1 Initial Baseline Period ................................ ................................ ............................. 57 4.3.2 First Loading ................................ ................................ ................................ ........... 58 4.3.3 Air- out Period after First Loading ................................ ................................ .......... 59 4.3.4 Second Loading ................................ ................................ ................................ ...... 60 4.3.5 Air- out Period after Second Loading ................................ ................................ ...... 61 4.3.6 Third Loading ................................ ................................ ................................ ......... 62 4.4 F IAM - pwp Predictions for Recent Residential Field Monitoring Studies ............................ 63 **Appendix A –**  **Summary o f E**  **PA Fo**  **rmaldehyde Pilot Study Appendix B**  **– Model Sensitivity**  **Appendix C –**  **Basis for Emission Classes Appendix D**  **– Historical Test** **ing o**  **f P WP**  **s t** **o Derive Slope a** **nd Intercept Values Appendix**  **E –**  **Derivation o f Two**  **- z** **one Steady -**  **s tate Solution** iii 

### LIST OF FIGURES Figure 2 - 1. FIAM

- pwp House Screen. ................................ ................................ ............................. 4 Figure 2 - 2. Popup Screen

– Create Your Own Structure Ty pe. ................................ ...................... 5 Figure 2 - 3. U.S. Climate Zones. ................................ ................................ ................................ ...... 5 Figure 2 - 4. Popup Screen

– Create Your Own Climate Zone. ................................ ........................ 6 Figure 2 - 5. FIAM

- pwp Source Screen. ................................ ................................ .......................... 14 Figure 2 - 6. Source Screen after Adding Default PWP Ty pes ................................ ....................... 15 Figure 2 - 7. Source Screen after Adding Custom Values ................................ ............................... 16 Figure 2 - 8. Exposure Screen ................................ ................................ ................................ .......... 21 Figure 2 - 9. Preparing to Add a New Exposure Group ................................ ................................ ... 23 Figure 2 - 10. Result Screen with First Two Exposure Groups Selected ................................ ........ 27 Figure 2 - 11. Emission-rate Parameters for FIAM - pwp Default PWPs in an Apartment. .............. 32 Figure 2 - 12. Formaldehyde Concentration Decline with Fast and Slow Decay Periods. .............. 34 Figure 3 - 1. Representation of Declining Emission Rate by Power- law Function vs. Exponential - decay

Model. ................................ ................................ ................................ ...... 44 Figure 3 - 2. Representation of Declining Emission Rate by Power- law Function vs. Exponential - decay

Model with Periods of Fast and Slow Decay . ................................ ......... 44 Figure 4 - 1. FIAM

- pwp House - Screen Inputs Used to Model Study of New California Homes. ................................ ................................ ................................ ................................ .... 65 Figure 4 - 2. FIAM

- pwp Source - Screen Inputs Used to Model Study of New California Homes. ................................ ................................ ................................ ................................ .... 66 Figure 4 - 3. FIAM

- pwp Results for Modeling of New California Homes. ................................ ..... 66 Figure 4 - 4. FIAM

- pwp Source - Screen Inputs Used to Model CDC Study of Travel Trailers. ..... 67 Figure 4 - 5. FIAM

- pwp Results for Modeling of Travel Trailers. ................................ .................. 67iv 

### LIST OF TABLES Table 2 - 1. House Dimensions and Calculated Volume for Five Housing Types ........................... 9 Table 2 - 2. Summer and Winter Indoor Temperatures from RECS 2005, by Climate Zone ........ 10 Table 2 - 3. Year-round Indoor Temperatures Derived from RECS 2005, by Climate Zone ........ 10 Table 2 - 4. Modeled Year-round Indoor RH Level, by Climate Zone ................................ .......... 11 Table 2 - 5. Alternative Analy tical/Regulatory

Options for EPA Formaldehyde Rule .................. 17 Table 2 - 6. Default Slopes and Intercepts for Six Default PWP Ty pes ................................ ......... 18 Table 2 - 7. Default Exposed Surface Areas (in m2 ) for Six PWP Ty pes, b y S tructure Type – New-home Case ................................ ................................ ................................ .................... 20 Table 2 - 8. Default Exposed Surface Areas (in m2 ) for Six PWP Ty pes, b y S tructure Type – Renovation Case ................................ ................................ ................................ .................... 20 Table 2 - 9. Default Annual Hours at Home and Non-home Locations, b y Exposure Group. ....... 24 Table 2 - 10. Default Concentration Values for Non -home Locations ................................ .......... 25 Table 2 - 11. Derivation of Baseline Values for Daycare, School and Work Locations ................ 26 Table 2 - 12. Concentration Values for Selected Non-home Locations, b y Emissions Scenario ................................ ................................ ................................ ................................ . 26 Table 2 - 13. Run Notes for Example 1 ................................ ................................ .......................... 30 Table 2 - 14. Run Notes for Example 2 ................................ ................................ .......................... 31 Table 2 - 15. Run Notes for Example 3 ................................ ................................ .......................... 31 Table 2 - 16. Run Notes for Example 4 ................................ ................................ .......................... 33 Table 2 - 17. Run Notes for Example 5, Part 1 (fast decay period) ................................ ............... 34 Table 2 - 18. Run Notes for Example 5, Part 2 (slow decay period) ................................ .............. 34 Table 4 - 1. Model Inputs (Sources and Sinks) for Initial Baseline Period ................................ ... 57 Table 4 - 2. Modeling Results for Initial Baseline Period ................................ ............................. 58 Table 4 - 3. Model Inputs (Sources and Sinks) for First (Medium) Loading ................................ 58 Table 4 - 4. Modeling Results for First Loading ................................ ................................ ........... 59 Table 4 - 5. Model Inputs for Air- out Period after First Loading ................................ ................. 59 Table 4 - 6. Modeling Results for Air- out Period after First Loading ................................ ........... 60 Table 4 - 7. Model Inputs (Sources and Sinks) for Second (High) Loading ................................ . 60 Table 4 - 8. Modeling Results for Second Loading ................................ ................................ ....... 61 Table 4 - 9. Model Inputs for Air- out Period after Second Loading ................................ ............. 61 Table 4 - 10. Modeling Results for Air- out Period after Second Loading ................................ .... 62 Table 4 - 11. Model Inputs (Sources and Sinks) for Third (High) Loading ................................ .. 62 Table 4 - 12. Modeling Results for Third Loading ................................ ................................ ........ 63 Table 4 - 13. Summary

of Recent Formaldehyde Field Monitoring Studies ................................ . 641



### 1. **INTRODUCTION** The model described in this document, the Formaldehyde Indoor Air Model - Pressed Wood Products , Version 2.0 ( FIAM - pwp v2.0 ) , is intended to assist the user in estimating human inhalation exposure to airborne formaldehyde emissions from composite wood products (CWPs 1 ) installed in new or existing residences , including small er structures such as camper trailers. The model estimates indoor formaldehyde concentrations and associated human inhalation exposures for such situations. FIAM - pwp i s an adaptation of a model developed during the 1980s by Dr. Thomas Matthews and colleagues 2 , 3 at the Oak Ridge National Laboratory . The “Matthews model” was designed to estimate the steady- state indoor formaldehyde concentration due to emissions from wood products in a single indoor compartment or zone. Product emission rates in the model are dependent on the formaldehyde concentration in the vapor phase

– as the concentration increases the emission rate s decrease , other things being equal. The initial ( “ steady- state ”) indoor concentration calculated by the model is assumed to decrease over time , as the formaldehyde “reservoirs” in various sources (or sinks) are gradually depleted. The decrease over time is assumed to follow a first- order exponential proces s, at a decay rate that corresponds to an assumed half life for the collective formaldehyde emissions . Inthe mid- 1990s , an EPA- sponsored pilot study was undertaken by

V ersar/GEOMET 4 to assess the contribution of UF -bonded wood products to formaldehyde levels in homes and to evaluate current EPA exposure models . Shortly after this study

was completed, Versar was tasked by EPA to develop a modified version of the Matthews model. The primary modifications were (1) estimation of steady- state formaldehyde concentrations for the case of a two - zone indoor environment , and (2) incorporation of reversible (re - emitting) indoor sinks. The modified model also included the option to be run in a single - zone mode. The model was not finalized due to shifting priorities at the time of its development. In2 006, formaldehyde from pressed wood products received national attention when the U.S. Federal Emergency

M anagement Agency

(FEMA) provided travel trailers and mobile homes for habitation by

residents of the U.S. gulf coast who were displaced by Hurricane Katrina and Hurricane Rita. Some individuals who moved into these temporary homes complained of breathing difficulties, nosebleeds, and persistent headaches. In December 2007 and January 2008, the Centers for Disease Control and Prevention measured formaldehyde levels averaging

1 In this report, the term “ composite wo od product” (CWP) refers only to hardwood plywood, medium density fiberboard, or particleboard whereas “pressed wood product” (PWP) refers to a broader set of wo od materials including, for example, softwood plywood and oriented strand board. 2 T. Matthews, T. Reed, B. Tromberg, C. Daffron, and A. Hawthorne. 1983. Formaldehyde Emissions from Com bustion Sources and Solid Formaldehyde Resin Containing Products: Potential Im pact on Indoor Formaldehyde Concentration and Possible Corrective Measures. Proceedings of ASHRAE Symposium Management of Atmospheres in Tightly Enclosed Spaces , Santa Barbara, CA. 3 T. Matthews, A. H awthorne, and C Thom pson. 1987. Formaldehyde Sorption and Desorption Characteristics of Gy psum Wallboard. Environmental Science &Technology 21: 629 - 634. 4 M. Koontz, H. Rector, D. Cade, C. Wilkes, and L. Niang. 1996. Residential Indoor Air Formaldehyde Testing Program: Pilot Study . Report No. IE - 2814, prepared by GEOMET Technologies, Inc. for the USEPA Office of Pollution Prevention and Toxics under EPA Contract No. 68 -D3 - 001 3, Washington, DC.2

77 parts per billion**5** , **6** (ppb; geometric mean) in a random sample of FEMA- supplied occupied travel trailers, park models, and mobile homes. InF ebruary 2 008 U.S. health officials announced**7** that potentially hazardous HCHO levels were found in both travel trailers and mobile homes provided by FEMA. In April 2008 the California Air Resources Board (CARB ) formally adopte d an Airborne Toxic Control Measure 8 (ATCM) to reduce formaldehyde emissions from CWP s sold, offered for sale, supplied, used, or manufactured for sale in California. On July 7 , 2010, the Formaldehyde Standards for Composite Wood Products Act (FSCWPA) was signed into law. This statute , which adds a Title VIto TSCA, establishes formaldehyde emission standards for hardwood ply wood, particleboard, and medium- density f iberboard that are identical to the CARB ATCM Phase II standards 9

. TSCA Title VI directs EPA to promulgate implementing regulations by January 1 , 2013 that address: sell -through dates for products; stockpiling; third-party testing and certification; auditing and reporting of third-party c ertifiers; recordkeeping; chain of custody; labeling; enforcement; products made with no - added formaldehyde (NAF) and ultra- low emitting formaldehyde (ULEF) resins; laminated products; finished goods; hardboard; and products containing de minimis amounts of composite wood products. As a result of the activity described above, EPA decided to revise and update, when possible, the formaldehyde model developed in the mid- 1990s to facilitate an assessment 10 of exposures before and after the EPA formaldehyde rule goes into effect. F IAM - pwp v1 .0 was the initial result of this effort , with FIAM

- pwp v2.0 developed in response to peer review and workgroup c omments. Version 2.0 adds exposure estimates to the model but indoor sinks have been excluded, f or reasons discussed later in this document (see **Section 3**  ). **Section 2**  describes the user interface for the model and **Section 3**  describes the mathematical basis , underlyingc alculations and related assumptions. Model evaluation , including comparison s to research-house and fieldmonitoring data , is provided in **Section 4**  . The EPA pilot study mentioned above is summarized in **Appendix A**  . Analys es related to model sensitivity a re presented in **Appendix B**  . The basis for emission classes used on the Source Screen is presented in **Appendix C**  . Historical chamber-test data, conducted primarily during the 1980s but extending into the 1990s and providing part of the basis for emission-rate parameters used in FIAM - pwp , are described and discussed in **Appendix D** . **Appendix E** describes the mathematical derivation of the two - zone implementation of the steadystate model.

5 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: http://www.cdc.gov/nceh/ehhe/trailerstudy/assessment.htm#final . July 2008 (amended December 2010). 6 DHS. 2009. FEMA Response to Formaldehyde in Trailers . OIG - 09 - 83. Department of Homeland Security, Office of Inspector General, Washingto n, DC. Available at: http://www.dhs.gov/xoig/assets/mgmtrpts/OIGr_09 - 83_Jun09.pdf . 7 See http://www.msnbc.msn.com/id/23168160/ns/us_news - life/t/cdc -tests - confirm- fema -trailers - are -toxic/ . 8 See http://www.arb.ca.gov/toxics/compwood/com pwood.htm for rec ent activity related to this ATCM. 9 Available at http://www.arb.ca.gov/toxics/comp wo od/com pwood.htm . 10 USEPA . 2012. Formaldehyde from Composite Wood Products: Exposure Assessment. Draft Fina l Report. U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics, Exposure Assessment Branch, 1200 Pennsylvania Avenue NW, Washington, DC 20460. July 2012.3



### 2. **USER INTERFACE 2.1**  **Background –**  **Model Versions** In2 009 an on- line , user- friendly version of the formaldehyde model (FIAM - pwp v1.0 ) was developed along with documentation 11 to guide its use. Later that same ye ar a peer review of the model was facilitated for EPA by E astern Research Group, Inc. (ERG). The purpose o f the peer review was to review and comment on three main aspects of the FIAM - pwp model: the soundness of the algorithms and exposure assumptions; the ease of use of the graphical interface; and the completeness and clarity o f the model documentation. Unedited written comments submitted by five reviewers in response to the peer- review charge were organized in a report 12 prepared for EPA b y ERG in October 2009. Version 2 , named FIAM

- pwp v2.0 and the subject of this document , was developed to run under the Internet Geographical Exposure Modeling System (IGEMS 13 ) platform . Some additions to or subtractions from the previous version are related, at least in part, to the peer reviewers ’ comments . For example, a decision was made to drop certain FIAM - pwp features that provided particular challenge s or difficulties : (1) inputs for indoor sinks, an area of considerable modeling uncertainty ; and (2) inputs for emission characteristics of cabinet components, which were very demanding. In addition, exposure groups are b eing handled differently in the current version, for consistency

with the approach used in EPA ’s 2012 formaldehyde exposure assessment . The user interface for the current version includes three input screens (House, Source and Exposure S creens) and an output screen (Result Screen) that displays the modeling results; these results are continually updated, such that any time the Result Screen is accessed the results displayed reflect all current inputs , much like a spreadsheet . First-time users, in particul ar, are advised to go through the input screens in sequence (i.e., House then Source then Exposure), examining results either “along the way” or after all inputs have been entered, at the user’s discretion. The House Screen is described in **Section 2.2**  , the Source Screen in **Section 2.3**  , and the Exposure Screen in **Section 2.4**  **.** For each of these screens a description of inputs and options is provided first, followed by the basis for model defaults. The Result Screen is described in **Section 2.5**  **.** Instructi ons f or accessing the model via the IGEMS portal are provided in **S ection**  **2.6** , along with documentation of ancillary mode l features such as saving runs for later access, printing inputs and results for a run, archiving inputs and results in Ex cel , and accessing the context- sensitive help embedded in the model . Example applications are provided in **Section 2.7.**

11 Formaldehyde Indoor Air Model

– Pressed Wood Products: Model Documentation . Prepared by Versar, Inc. for EPA/OPPT by under Contract No. EP -W - 04,035, Work Assignment No. 4 - 2. August 2009. 12 Peer Review Results for the Formaldehyde Indoor Air Model

– for Pressed Wood Products . Prepared by Eastern Research Group, Inc for EPA/O PPT under Contract No. EP -W - 05 - 014. October 2009. 13 See http://www.epa.gov/oppt/exposure/pubs/gems.htm .4

**2. 2**  **House Screen** This screen (see **Figure 2**  **- 1**  ) is intended to collect information on the house volume and internal conditions (e.g., temperature, airflows ) and to provide certain options pertaining to model calculations. The inputs here can be divided into three screen portions: (1) documentation of the run and selection of structure ty pe and climate zone (upper portion), (2) editable information on the number of zones, zone volumes and airflows (middle portion); and (3) indoor conditions and formaldehyde decay

parameters (lower portion).

**Figure 2 -**  **1. FIAM** 

**- pwp**  **House Screen.** M any of the inputs on this screen are optional, in the sen se that default values are provided by the model. The choice of structure type on the upper portion of the screen provides default values for zone volumes and airflow rates , which are displayed on the middle portion of the screen. The choice of climate zone on the same line provides default values for indoor temperature and humidity, which are displayed on the lower portion of the screen. Other inputs on the lower portion (e.g., background concentration) are not linked to any user choice but do have default values. Although the model can be run using default value s, care should be taken in choosing the ty pe of structure to be modeled and in choosing appropriate values for inputs such as the background concentration, emissions half life, and indoor temperature and relative humidity . **2.2.1 Inputs and Options**  **Run Title**  **and Run**  **Notes .**  Text inputs for these two items are intended to assist the user in documenting the purpose of the model run along with certain choices made or options exercised . **Structure Type and Climate Zone**  **.** Both o f these items have pick lists from which the user can choose to obtain default values, which can either be used “ as is ” or edited. The user also has the option of creating additional structure types or climate zones and saving them for later use. There are five default s tructure ty pes in FIAM

- pwp : single - family (SF) detached homes; SF attached homes; a

partments; manufactured/mobile homes , and camper trailers. The SF detached/attached homes are two - story structures with two zones (up stairs and downstairs) whereas the others are single - zone structures . **Upper Portion Middle Portion** 

**Lower Portion** 5

The values associated with FIAM - pwp default structure ty

pes are “untouchable” (i.e., they cannot be directly

e dited) , but the choices on the pick list include one called Create Your Own Structure Ty pe – if this choice is made , then the popup screen shown in **Figure 2**  **- 2**  will appear. At that point, the user assigns a structure ty pe name and enters zone descriptions, volumes and airflows, and then clicks the **Save** button. The **MAKEACOPY** button (see **Figure 2**  **- 1**  , above) is used to copy and then edit/save any

o f the default choices . Guidance on entering volume and airflow values is provided later in this s ection , under the heading **Zones, Volumes and Air Flows** .

**Figure 2 -** **2. Popup Screen –**  **Create You r Own Structure Type.**  FIAM - pwp uses the U.S. climate zones defined by the Department of Energy ( see **Figure 2**  **- 3**  ) There are five climate zones, numbered 1 though 5 , with 1 being the coldest and 5 the warmest.

**Figure 2 -** **3. U.S. Climate Zones.** Source : U.S. Energy Information Administration (http://www.eia.doe.gov/emeu/cbecs/climzonenew.gif )6

As with default structure ty pes, the values associated with default climate zones in FIAM - pwp are “untouchable.” Other values can be assigned and saved via a choice called Create Your Own Climate Zone , which is included on the climate - zone pick list

– if this choice is made , then the popup screen shown in **Figure 2**  **- 4**  will appear. At that point, the user assigns a name , enters the desired temperature and humidity values, and clicks the **S AVE**  button. The **MAKEACOPY** button on the main screen can be used to cop y and then edit/save any of the default choices . Regardless of the climate zone chosen, the user can override the associated temperature and humidity values by changing them directly

in the lower portion of the House S creen.

**Figure 2 -** **4 . Popup Screen**  **– Create Your Own Climate Zone.**  **Air Exchange**  **Rate.** This item is “graye d out” because no user entry i s allowed here ; the rate is displayed for informational purposes only . The value displayed is calculated by FIAM - pwp using volume and airflow information and, thus, can be changed by editing those inputs. **Zones, Volumes**  **and Air**  **Flows.** Houses in FIAM - pwp can have either one or two zones. Among the default structure ty pes, single - family detached and attached homes are conceptualized as having two separate zones (upstairs and downstairs) whereas manufactured homes, apartments and camper trailers are conceptualized as having a single zone. The maximum number of zones allowed is two. Thus, for example, to represent a house with three stories , at least two of the three stories would need to be combined into one zone. The indooroutdoor airflow rates determine the air exchange rate. For example, for an apartment with a volume of 261 m3 , the default indoor- outdoor airflow rate of 52.2 m 3 /h results in an air exchange rate of 0.2 ACH (i.e., 52.2 m 3 /h / 262 m3 = 0.2/h). If the user selects Create Your Own Structure Type from the pick list or edits one of the default choices after making a copy, then the popup screen previously shown in **Figure 2**  **- 2**  will appear. The required information includes the name of the structure ty pe, the description and volume for each zone , and airflow rates. For a one - zone house only the first line needs to be completed and only two air flows are needed

– Flow from Outside and Flow to Outside . These flows must be equal to provide an overall flow balance for the house. For a two - zone house six airflows are needed

– the flow for each zone to and from outdoors plus the flows in both directions between the two zones. Individual flow pairs (e.g., flow from and to outside for zone 1) do not necessarily need to be balanced, but the total flow out of a zone shoul d match the total flow into it. On the main screen, the program updates the total flow per zone as the user provides or edits inputs. If the total flows for any

z one are not balanced, then the program raises a flag by assigning a red font to the zone total s . The model still will run in such cases , but the user is advised of the possibility

of counterintuitive or misleading results. The default air flows are balanced, that is, the airflow rate from outdoors to indoors is equal to that from indoors to outdoors. For two - zone structures

– SF detached /attached homes

– the house volume is equally

a pportioned between upper /lower stories and identical indoor- outdoor airflow7

rates are assumed per story . Further, as an expedience, it is assumed that the airflow rate b etween the two indoor zones is balanced and equal to the indoor- outdoor airflow rate. Thus, for example, for a SF detached home with a volume of 811 m 3 or 405.5 m 3 per story, both the indoor- outdoor airflow rate per story

and the interzonal airflow rate between stories are set at 81.1 m 3 /h. If one of the default two - zone homes is selected but the user prefers to treat the home as a single, well -mixed zone, then FIAM - pwp will add the zone volumes and will “collapse” the airflow rates to the single - zone cas e, meaning that the only flow information needed is the airflow rates from outdoors to indoors and vice versa. For the single - zone case these two airflow rates should have the same value. If the number of zones is changed back to two, then the program will revert to the volumes and airflow rates originally associated with these house types. **Background Concentration.**  This concentration

– the first of eight inputs on the lower portion of the H ouse Screen

– is intended to reflect the contribution to the indoor formaldehyde concentration of both the outdoor concentration and indoor sources other than PWPs (e.g., tobacco smoke, permanent press fabrics, paints, cosmetics ). The FIAM - pwp default value for the background concentration is 7.5 ppb. If a value of zero is chosen for the background concentration, then the modeling results will reflect only the contributions of the indoor sources selected for the model run via inputs on the Source Screen . **Emissions Half**  **Life.** This input governs the rate at which indoor formaldehyde concentrations decay over time. The FIAM

- pwp default value is 1.5 years ; with this half life, the emission rate 10 years after new construction would be about 1% of the initial value. With a half life of 3 .0 ye ars it would take 20 years (i.e., t wice as long) to reach 1% of the initial value. **Temperature and**  **Humidity.** Model algorithms to predict initial indoor formaldehyde levels include temperature and humidity adjustments for the emission rate from PWPs . Default values for indoor temperature and relative humidity are assigned based on the user’s choice (or creation) of a climate zone. These defaults can be edited directly on the lower portion of the screen, but if that is done then these new values would only b e associated with the saved run name . Alternatively, values can be saved for access in any run by creating a new climate zone or by copying and editing an existing one (see **S tructure Type and**  **Climate Zone** , earlier in this section). **Time from**  **‘ Initial**  **Concentration ’**  **and ‘**  **Decay Concentration**  **to '**  **.** By default, FIAM

- pwp “decays ” initial indoor concentrations that are calculated under a steady- state assumption to time points that are 3 , 6 and 12 months later than the initial point in time. The input labeled ‘ Time from Initial Conc ’ (see **Figure 2**  **- 1**  ) enables the user to specify an additional point in time (in months) over which the model decays the initial concentration values; this input is set to 24 months by default. The input labeled ‘ Decay C oncentration to ’ , with a default of 10 ppb , allows the user to specify a concentration for which the model will calculate the time to decay from the initial modeled concentration to that value. For a two - zone structure, the model will calculate this decay time based on the higher of the zone - specific initial modeled concentrations . **Temperature and**  **Humidity Coefficients.**  The model initially c alculates indoor concentrations at an indoor temperature of 23  C and an indoor relative humidity of 50 percent, and then adjusts the results to the temperature and humidity conditions selected by the user . The temperature and humidity coefficients specified here are used by the model to make these adjustments.8

**2.2. 2**  **Basis for Defaults Structure**  **Type.** The five default structure ty pes in FIAM

- pwp are the same as those used in the EPA’s Formaldehyde from Composite Wo od Products: Exposure Assessment dated March 2012. C ollectively, they account for the major ty pes reported by the American Housing Survey (AHS) (http://www.census.gov/hhes/www/housing/ahs/ahs.html) and the Residential Energy C onsumption Survey (RECS) (http://www.eia.doe.gov/emeu/recs/): single - family (SF) detached homes; SF attached homes; a

partments; and manufactured/mobile homes or trailers. For the purpose of estimating structure volume, a further distinction was made for manufactured homes due to size differences

– single -wide (SW) versus double -wide (DW). Camper trailers and park models also are o f interest because, like manufactured homes, these housing ty pes have been used for some residents displaced by

natural disasters such as Hurricane Katrina . Camper trailers were chosen to represent the small -volume temporary housing for displaced residents , as this housing ty pe accounted for 80 percent of the smaller-volume structures that were tested as part of FEMA’s formaldehyde monitoring in temporary housing 14 , 15

. For SF detached/attached homes, apartments, and manufactured homes, default structure volu me s were calculated based on statistics resulting from the U.S. Department of Energy ’s 2005 RECS 16 , using the reported average floor area for the most recently built category (ye ars 2000 - 2005) and assuming a ceiling height of 8.5 feet. For camper trailers, a ty pical size used for displaced hurricane victims was assigned , with an assumed ceiling height of 7 feet. The following floor areas and associated dimensions were assumed for the five structure typ es: 1. SF detached home

– 3456 sq ft (36 ft x 48 ft, 2 stories) 2. SF attached home

– 2240 sq ft (28 x 40 ft, 2 stories) 3. Apartment

– 1120 sq ft (28 ft x 40 ft) 4. Manufactured home

– 1216 sq ft (16 ft x 76 ft) for SW; 1680 sq ft (28 ft x 60 ft) for DW 5. Camper trailer

– 328 sq ft (8 ft x 35 ft with 4 ft x 12 ft “slide - out”). The dimensions chosen for SF homes and apartments were consistent with their respective average floor areas as reported in the RECS 2005 survey results. The dimensions listed above are exterior dimensions; for interior volume calculations, 0.5 ft was subtracted from both the length and width to account for the area occupied by exterior cladding, sheathing, studs and wallboard. For SF homes a simplifying assumption was made that the upper and lower floors are of identical dimensions. For manufactured homes, a weighted average of SW and DW volumes was used; based on statistics from the U.S. Census Bureau’s Manufactured Home Survey

(MHS) for years 2000 - 2009 (http://www.census.gov/const/www/mhsindex.html), 70 percent of the manufactured homes were assumed to be the double -wide ty pe. The resultant house volumes are listed , along with the house dimensions, in **Table 2 -**  **1** . 14 Centers for Disease Control and Prevention . 2008/2010. Final Report on Formaldehyde Levels in FEMA -Supplied Travel Trailers, Park Models, and Mobile Homes . July 2008 (amended December 2010). Available at: http://www.cdc.gov/nceh/ehhe/trailerstudy/assessment.htm#final . 15 D epartment of

H omeland Security . 2009. FEMA Response to Formaldehyde in Trailers . OIG - 09 - 83. Office of Inspector General, Washington, DC. Available at: http://www.dhs.gov/xoig/assets/mgmtrpts/OIGr_09 - 83_Jun09.pdf . 16 See, for example, http://www.eia.doe.gov/emeu/recs/contents.html .9

**Table 2 -**  **1. House Dimensions and Calculated Volume for Five Housing Ty pes**  **Housin g Type**  **Number of**

**Stories Length,** 

**ft Width,** 

**ft Ceiling** 

**Height, ft Volume,** 

**ft 3**  **(m 3**  **) SF Detached**  2 48 36 8.5 28,666 (811) **SF Attached** 2 40 28 8.5 18,466 (523) **Apartment** 1 40 28 8.5 9,233 (261) **Manufactured Single** **- wide**  **Double -** **wide Average** **a** 1

1 1 16

28

-- 76

60

-- 8.5

8.5 8.5 9,947 (282)

13,908 (394) 12,720 (360) **Camper Trailer Main body**  **Slide -** **out** 1

1 35

12 8

4 7

7 2,147 (61) a Weighted average of single -wide (30 %) and double -wide (70 %); see text. **Climate Zone / Temperat** **ure and Humidity.** Default indoor temperature -values were determined for each of five U.S. climate zone s using responses to RECS 2005 survey questions about usual temperatures maintained in the residence. One of the questions

– “At what temperature does your household usually keep your home in the winter?”

– was asked under three conditions: (1) during the day when someone is home; (2) during the day when no one is home; and (3) during sleeping hours . The same set of questions also was posed with reference to the summer season. As described in the exposure assessment report cited in **Section 1**  of this document , the RECS database was analyz ed for these questions to estimate the year-round average temperature in each climate zone. **Table 2**  **- 2**  summarizes response s to the RECS questions on day time temperature when someone is home and nighttime (sleeping hours) temperature by c limate zone. The columns labeled “Overall” are weighted averages of the day time and nighttime average temperatures for summer and winter, with weights of 2/3 for day time and 1/3 for nighttime. The overall summer and winter temperatures, in turn, were averaged to derive a year-round average temperature, by

weighting the season - specific averages by the number of months associated with each. The resultant ye ar- round temperature estimates are listed in **Table 2 -** **3** .10

**Table 2 -** **2. Summer and Winter Indoor Temperatures from RECS 2005, by Climate Zone U.S.**  **Climate Zone**  **Average Summer Temperature Average Winter Temperature** 

**Day Night**  **Overall Day**  **Night Overa** **ll 1 (coldest)**  73.4 73.3 73.4 69.1 65.8 68.0 **2** 73.0 73.0 73.0 69.6 67.6 68.9 **3** 73.2 73.2 73.2 69.8 68.1 69.3 **4** 73.9 73.2 73.7 70.9 68.6 70.1 **5 (warmest)** 75.1 74.8 75.0 72.4 70.6 71.8 **Table 2 -** **3. Year** **- round**  **Indoor Temperatures Derived from RECS 2005, b y Climate Zone**  **U.S. Climate**  **Zone Summer**  **Temp erature**  **Winter Temp erature**  **Year -** **Round Temperature**  **Average Temperature**  **Number of**

**Months Average** 

**Temperature Number of** 

**Months 1 (coldest)**  73.4 3 68 .0 9 69.4 **2** 73.0 4 68.9 8 70.3 **3** 73.2 4 69.3 8 70.6 **4** 73.7 5 70.1 7 71.6 **5 (warmest)** 75.0 7 71.8 5 73.6 The RECS does not ask about humidity l evels maintained in the residence. Consequently, a mass -balance modeling approach was applied to estimate the ye ar- round average indoor relative humidity (RH) level for each climate zone. A representative city was chosen for each zone:  Climate Zone 1

– Milwaukee, WI  Climate Zone 2

– Chicago, IL  Climate Zone 3

– New York, NY  Climate Zone 4

– Charlotte, NC  Climate Zone 5

– Houston, TX . Hourly outdoor temperatures for a ty pic al meteorological year 17 (TMY) were obtained for each city as inputs to a mass -balance model. The modeling approach, described in the formaldehyde exposure assessment report cited in **Section 1**  , is consistent with methods described in American Society f or He ating, Refrigerating and Air- Conditioning Engineers (ASHRAE) Standard 160P ( Criteria for Moisture - Control Design Analys is in Buildings) . In the mass -balance model, moisture in the indoor air is determined by moisture in the outdoor air, indoor moisture generation by the occupants, and moisture removal by a central air- conditioning (AC) system. 17 Available at http://rredc.nrel.gov/solar/old_data/nsrdb/1991 - 2005/tmy3/ .11

Model ed indoor RH levels for each climate zone are listed in **Table 2**  **- 4**  for two cases

– with and without an AC unit. The effect of the AC unit is most pronounced in H ouston, due primarily to the higher outdoor temperature and, hence, the greater AC run time leading to greater moisture removal . Because the vast majority o f the U.S. housing stock has air conditioning 18 , the estimated RH values with AC were used in assigning default humidity values . **Table 2**  **- 4**  **. Modeled Year -**  **round Indoor RH Level, by Climate Zone Climate Zone**  **RH Level with AC**  **RH Level with**  **out AC**  **1 (coldest)** 59.1% 63.8% **2** 58.1% 64.7% **3** 56.3% 66.4% **4** 59.8% 72.6% **5 (warmest)** 61.4% 85.3% **Air Exchange**  **Ra te**  **and Airflows**  **.** The default indoor- outdoor airflows in FIAM - pwp were chosen such that the air exchange rate for each of the default structure ty p es is 0.2 air changes per hour (ACH). For the exposure assessment report cited in **Section 1**  , the focus is on P WPs in new housing; thus, a default value was chosen that lies toward the lower end of the distribution, as newer structures tend to be better sealed and have lower air exchange rates. For residences, the Exposure Factors Handbook ( EFH ) suggests 0.45 ACH as a central value and 0.18 as a lowerend value, based on statistic s developed by Koontz and Rector 19 (1995) from a database of perfluorocarbon tracer (PFT) measurement results. The EFH also cites Murray and Burmaster20 (1995), who used the same PFT database to summarize distributions for data subsets defined by climate region and season ; from that analys is, the 10 th percentile value ranged from 0.1 to 0.3 ACH across climates and seasons, averaging about 0.20 ACH. In a more recent study

by Offerman et al. 21 (2008) on ventilation and formaldehyde in new California homes, the 25 th percentile value for air exchange rate was 0.2 ACH for the two larger subsets of homes that were studied. In a study b y Maddalena22 (2008) concerning chemical

18 According to the Residential Energy Consumption Survey, 84 percent of U.S. housing units had air- conditioning equipment as of 2005 ( see http://205.254.135.24/emeu/recs/recs2005/hc2005_tables/detailed_tables2005.html). 19 M.D. Koontz and H.E. Rector. 1995. Estimation of Distributions for Residential Air Exchange Rates . Report prepared for EPA/OPPT under Contract No. 68 -D9 - 0166, Work Assignment No. 3 - 19. 20 Burmaster D.M. Murray and D.E. Burmaster. 1995. Residential Air Exchange Rates in the United States: Em pirical and Estimated Parametric Distribution by Season and Climatic Region. Risk Analysis 15: 459 -465. 21 F. J. Offermann, J. Robertson, D. Springer, S. Brennan, and T. Woo. 2008. Window U sage, Ventilation, and Formaldehyde Concentrations in New California Homes: Summer Field Sessions. ASHRAE IAQ 2007 Conference , Baltimore, MD. 22 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 Techno logies Division, Berkeley, CA. Available at: http://www.cdc.gov/nceh/ehhe/trailerstudy/pdfs/LBNL - 254E.pdf .12

emissions in four FEMA temporary housing units (camper trailers), the measured air exchange rate varied from 0.15 to 0.39 ACH across the trailers, averaging 0.25 ACH. Persily et al. 23 (2010) modeled air infiltration rate distributions for the U.S. housing stock; for single - family homes built in 1990 or later, the 25 th percentile value was 0.15 ACH and the 50 th percentile value was 0.26 ACH. Given the above statistics, 0.2 ACH was chosen as the value to represent new home s, including detached/attached homes, apartments, manufactured homes, and camper trailers. For the renovation case that also was examined as part of the formaldehyde exposure assessment, a central value such as 0.45 ACH, as suggested in the EFH , may b e more appropriate. However, the data on which that suggested value is based are somewhat dated and there has been a general tendency toward increasing airtightness of U.S. homes over time; for ex ample, the median value reported for the Offerman et al. (2008) study was 0.33 ACH. Thus, a value of 0.40 ACH

– double that use d for new homes – is suggested for the renovation case. As noted above, the indoor- outdoor airflow rates determine the air exchange rate. For example, for an apartment with a volume of 261 m3 , the default indoor- outdoor airflow rate of 52.2 m 3 /h results in an air exchange rate of 0.2 ACH (i.e., 52.2 m 3 /h / 262 m3 = 0.2/h) . The default air flows are balanced, that is, the airflow rate from outdoors to indoors is equal to the rate from indoors to outdoors. For two - zone structures

– SF detached or attached homes – the house volume is equally a pportioned between the upper and lower stories/floors and identical indoor- outdoor airflow rates are assumed for each story . Further, as an expedience, it is assumed that the airflow rate between the two indoor zones is balanced and equal to the indoor- outdoor airflow rate. Thus, for example, for a SF detached home with a volume of 811 m 3 or 405.5 m 3 per story, both the indoor- outdoor airflow rate for each story and the interzonal airflow rate between stories are set at 8 1.1 m 3 /h. **Background Concentration.**  Although no studies have been conducted with the explicit purpose of characterizing the background concentration, such a value conceivably can be inferred from concentration distribution s characterized via field monitoring studies. For example, if a field study were to focus on existing (as opposed to new) homes, then those toward the lower end of the concentration distribution presumably would be older homes with aged P WP sources and, thus, indicative of the background formaldehyde concentration. As noted in Section 3.3 of the exposure assessment report cited in **Section 1**  of this document , the results of field studies , when examined in this manner, indicate that an appropriate value for the residential formaldehyde background concentration would lie between 5 and 10 ppb. The midpoint of this range – 7.5 ppb

– was chosen as the FIAM - pwp default value for the background concentration. **Emissions Half**  **Life.** As described in **Section 3.**  **8** of this document, suggested values for the formaldehyde emissions half life, reflecting its decay indoors over time, range from 1.5 to 3 ye ars. An estimate of 2.92 ye ars was based on a cross - sectional analys is of homes of varying ages, as a proxy for time - series data from one or a few homes. If none of the materials or furnishings in such homes were changed by the occupants, then this approach might provide an unbiased estimate of the half life. However, as a house ages the occupants will tend to add or 23 A. Persily, A. Musser, and S.J. Emmerich. 2010. Modeled Infiltration Rate Distributions for U.S. Housing. Indoor Air 20: 473 -485.13

replace materials and furnishings, some o f which may emit formaldehyde. The addition of these new sources will result in higher concentration than in the case where no new sources were introduced. As a result, the cross - sectional analys is will yi eld an artificially low estimate of the decay rate, which means an artificially high estimate of the half life. Thus, 2.92 ye ars is best viewed as an upper-bound estimate. A more likely value, based on chamber studies of collections of pressed wood products as they age, is within the range of 1.5 to 2 ye ars. A half life of 1.5 ye ars was chosen as the FIAM - pwp default value; with this half life, the emission rate 10 ye ars after new construction would be about 1% of the initial value. **Temperature and**  **Humidity Coefficients.**  The default values for these coeffi cients

– 9799 for temperature and 0.01 7 5 for humidity

– are based on tests by Berge et al. 24 involving two Nor wegian particleboard specimens. These default values were used by HUD in setting the 1984 standards for particleboard and hardwood plywood paneling , and also have been used in ASTM, ANSIand Composite Panel Association ( CPA) standards or guidelines. The chamber tests underlying these coefficients were conducted at two temperature settings (22 and 28  C) and two relative humidity settings (30 and 60 % ). An alternative set of coefficients

– 8930 for temperature and 0.0195 for humidity

– derives from work by Myers 25 , who reviewed the extant literature and based his recommended temperature coefficient on chamber testing of about 40 specimens (particleboard and hardwood plywood paneling) from 11 laboratories. The temperature range of the se te sts was from 20 to 40  C. He also developed a humidity coefficient, but expressed little confidence in the number; the relative humidity 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. The HUD standard was promulgated before Dr. Myers completed his work.

24 A. Berge, B. Mellagaard, P. Hanetho, and E. Ormstad. 1980. Formaldehyde Release from Particleboard

– Evaluation of a Mathematical Model. Holz Als Roh - und Werkstoff 38: 252 - 255. 25 G. Myers. 198 5. The Effects of Temperature and Humidity on F ormaldehyde Emission from UF -bonded Boards: A Literature Critique. Forest Products Journal 1985: 35:20 - 31.14

**2.3 Source Screen**  This screen (see **Figure 2**  **- 5**  ) enables the user to specify the ty pes and amounts of wood products used or installed in the house , the zone(s) in which each ty pe is located, and input parameters (slope and intercept) that govern the formaldehyde emission rate. Following a description of each ty pe of input, guidance is given on choosing default inputs and/or adding custom inputs on this screen.

**Figure 2 -**  **5. FIAM**  **- pwp**  **Source Screen. 2.3.1**  **Types of Inputs PW** **P Type.** There are six default PWP ty pes in FIAM

- pwp :  Ori ented strand board (OSB) or softwood plywood (SWPW), ty pically used as underlay ment  Particleboard, often used as the platform to which a countertop laminate is affixed  Medium density

fiberboard (MDF) , often used in cabinet drawers and/or shelves  Coated CWP s (e.g., interior doors that are primed/painted, viny l - covered molding)  Hardwood plywood (HWPW) , often used for wall paneling and sides/backs of cabinets or entertainment centers  HWPW laminate , with uses similar to HWPW but made by affixing a wood veneer to a particleboard, medium- density fiberboard, or veneer- core platform . A distinction is made between HWPW and HWPW laminate because EPA may regulate these two PWP ty pes differently. **Em ission**  **Class.** Default values for FIAM - pwp emission-rate parameters (slope and intercept) have been developed for four emission classes: Baseline; CARB1; CARB2; and NAF. As described below, t hese emission classes correspond to analytical or regulatory options that have been included by EPA as part of the considerations for a formaldehyde rule. **Slope and**  **Intercept.** These two parameters govern the emission rate from PWPs, including dependence of the emission rate on the indoor formaldehyde concentration. The s lope is a mass transfer coefficient that reflects the “backpressure” eff ect26 of the indoor formaldehyde concentration on the emission rate , whereas the intercept reflects the hy pothetical emission rate when the indoor formaldehyde concentration is zero. 26 See, for example, M.A. Jay jock . 1994. Back Pressure Modeling of Indoor Air Concentration from Volatilizing Sources, Am. Ind. Hyg. Assoc. J . 55 (3): 230 - 235.15

**Equilibrium Concentration.**  The equilibrium concentration (mg/m 3 ) displayed for each source is a calculated quantity – intercept (mg/m2

-hr) divided by slope (m/hr)

– that cannot be edited by the user; it is the theoretical maximum concentration that would occur if that were the only indoor source, with an arbitrarily l arge expose d surface area. The equilibrium concentration is indicative of the relative strength of emissions from each source. Lower- emitting sources, such as oriented strand board (O SB ) or softwood plywood ( SWPW) , can act as net “absorbers” (i.e., indoor sinks) in the presence of higher- emitting sources, due to the backpressure effect. **Location (Zone)**  **and Exposed**  **Surface Area.**  If a two - zone structure is being modeled, then sources can be assigned to either or both of the two zones. As discussed later (see **Section 2.3**  **.2** and **Section 2.3.3**  ), one input line is required for each source ty pe in each zone. The default amounts of exposed surface area for sources in FIAM - pwp are the same as those used in EPA’s Formaldehyde from Composite Wood Products: Exposure Assessment date d March 2012 . The exposed surface area (in m2 ) for a PWP can be viewed as its loading rate (in m2/m3 ) multiplied by the structure volume (in m3 ). **2.3.2 Adding Defau**  **l**

**t Input s**  Each input line or row entered on the Source Screen refers to a specific ty pe of source in a specific zone. For any of the five default structure ty pes, the simplest way

to add a group of sources is using the **Add Default**  **PWP Types**  button

– taking this action loads each of the six default PWP ty

pes in each applicable zone (zone 1 for a partments, manufactured homes and trailers; zones 1 and 2 for SF detached/attached structures). **Figure 2**  **- 6**  shows the Source Screen after this action has been taken. In loading these defaults, there is a choice of Emission Class (baseline, CARB1, CARB2, or NAF) and Case (new-home or renovation). The example shown in the figure is for apartments, with baseline emissions and the new-home case. As indicated in the figure, user selections are made , or inputs are provided , in the lower portion of the screen ; thes e choices/entries are then displayed in the upper portion.

**Figure 2 -**  **6. Source Screen after Adding Default PWP Types Display Area** 

**Selection Area**16

Once added, any default can be removed or edited using the **Remove**/**Edit** buttons to the right. Alternatively, sources can be “turned off” by un - checking the corresponding check-box to the left. The column to the left of PWP Type indicates whether a given line or row in the table is a FIAM - pwp default (D), revision (R) of a default, or newly created (C). For example, when a default source is edited, the character in this column will change from D to R. If the line is later changed back to the default values for area, source and intercept ( either by re - editing values or by using the **Restore** button), then the character displayed in the corresponding column will revert to D. Sources also can be added, one at a time, using the **Add** button. Inaddition to Emission Class and Case, choices need to be made for PWP Ty pe and Area. The default area for any combination of PWP and zone, displayed to the right, can be changed before clicking the Add button; after the button is clicked, the area (or any other value on that line) can be changed using the **Edit** button. Ine ither case, any source for which default values have been changed will be marked with an R in the second column. All sources chosen or added can be removed at once using the **Clear List** button. The maximum number of sources allowed by FIAM - pwp is 20. **2.3.3 Adding Custom Inputs**  Beyond adding default sources, the user al so can add new sources and associated values using the **Add Custom Values** button; this is the only way to add sources if a structure ty pe other than one of the defaults has been chosen. Inputs are required for the name of the PWP Ty pe , the Emission Class, the Zone (1 or 2), and values for Area, Slope and Intercept. **Figure 2**  **- 7**  shows the appearance of the Source Screen after using this button to add one source line.

**Figure 2**  **- 7. Source**  **Screen after Adding Custom Values 2.3.3**  **Basis for Defaults** As noted above, the default PWP ty pes available in FIAM

- pwp are those used in the EPA 2012 formaldehyde exposure assessment. The four emission classes in FIAM - pwp , which correspond to analytical or regulatory

options under consideration by EPA for a forthcoming formaldehy de rule, are described briefly

in **Table 2**  **- 5**  . EPA is considering some options bey ond those listed, such as exclusion of HWPW laminates from the CARB1, CARB2 and NAF options. The basis for these classes is described in some detail in Section 4.4.8 of the report on EPA’s formaldehy de exposure17

assessment, which is reproduced as **Appendix C**  in this document. In brief, within each emission class or regulatory

option, a certain percentage of each product ty pe is assumed to be in compliance with an existing sta

ndard such as CARB1; the se assumed percentages vary across the emission classes. The procedure for estimating the emission rate for each product ty pe, assuming that it meets a given standard, is described below. **Table 2**  **- 5**  **. Alternative Analytical /Regulator** **y Options**  **for EPA Formaldehyde Rule Option**  **a Description**  Baseline Estimated emission levels (year 2013) in the absence of an EPA rule. CARB1, Including Laminate d Products All CWPs, including laminated products, are at emission levels that meet CARB b Pha se 1 standards. Products that meet CARB Phase 1 standards at baseline are assumed to remain at that emission level. CARB2/Statutory Option , Including Laminate d Products 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. NAF c , Including Laminate d Products 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. a Corresponds to emission class used in FIAM - pwp b California Air Resources Board c No added formaldehyde **Slope and**  **Intercept. Appendix**  **D** of this document lists emission-rate parameters for various ty pes of PWPs that were derived from sets of chamber tests conducted during the 1980s and up through the mid- 1990s. Although the results from the se tests are somewhat dated, an important distinguishing feature is that all such tests 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. Equation 3 - 6 in **Section 3.**  **2** of this document is used as a basis for determining the intercept that is associated with a product meeting a certain emission standard, under the assumption that the air entering the chamber is formaldehyde - free : b = C

SS * (1 + m * Area / Q) * (Q / A rea) (Eqn. 2.1 ) where: b = intercept

– the emission rate at zero concentration in the air (mg/m2

-hr) C SS = steady- state formaldehyde concentration in the chamber (mg/m 3 ) m = slope

– the mass transfer coefficient (m/hr) Area = exposed surface area of the product (m2 ) Q = airflow rate into / out of the chamber (m 3 /hr)

= air exchange rate (1/hr) x chamber volume (m 3 )18

ASTM E1333 - 10 27 is a commonly used method for demonstrating compliance with formaldehyde emission standards. The method prescribes an air exchange rate for testing of 0.5 ACH and product loading ratios of 0.43 m2/m 3 for PB, 0.95 m2/m3 for HWPW , and 0.26 m2/m3 for MDF. Using these rates along with an assumed slope (m ) for a given PWP ty pe, the corresponding intercept can be determined for a hy pothetical source that just meets a given emissions standard . The assumed slope for each PWP ty pe i s the average of the slopes across all sets of emission tests for that ty

pe (after excluding statistical outliers in certain cases), as listed in **Appendix D.**  For example, the CARB2 emission standard for MDF is 0.11 ppm or 0.135 mg/m3

. An arbitrary chamber volume of 100 m 3 , which together with an air exchange rate 0.5 /hr yi elds a value of 50 m 3 /hr for Q , was used in the calculation. The volume does not matter here , as the exp osed surface area scales to volume via the loading ratio ; with a volume of 100 m 3 the corresponding surface area is 26 m2 . A slope of 1.06 m/hr i s assumed; this value is the average slope from about 30 sets of chamber tests of different MDF specimens . Sub stituting the assumed values given above into Eqn. 2 - 1 , 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 m 3 / 26 m2 ) = 0.40 mg/m2

-hr **Table 2**  **- 6**  lists the assumed slopes and calculated intercepts for each default PWP ty pe, using the procedure described above and assuming a mix of products meeting different standards within each emission class, as described in **Appendix C**  **.**

**Table 2 -**  **6 .**  **Default Slopes and In tercepts for Six Default PWP Types**  **PW P Type**  **Slope Intercept by Emission Class:**  **Baseline CARB1**  **CARB2 NAF**  OSB/SWPW a 0.61 0.03 0 0.03 0 0.03 0 0.03 0 Particleboard 0.70 0.131 0.124 0.12 2 0.03 0 MDF 1.06 0.281 0.27 1 0.26 9 0.128 Coated CWP 0.52 0.082 0.074 0 .071 0.02 2 HWPW 0.27 0.04 2 0.02 5 0.02 1 0.013 HWPW Laminate 0.27 0.04 2 0.02 3 0.02 1 0.013

a This relatively low- emitting PWP is not subject to any emissions standard .

27 ASTM. 2010. Standard Test Method for Determining Formaldehyde Concentrations in Air and Emission Rates from Wood Products Using a Large Chamber. Designation E1333 - 10, American Society for Testing and Materials.19

**Exposed Surface Area.**  The default amounts of exposed surface area for sources are the same as those used in EPA’s 2012 formaldehyde exposure assessment. As described in Section 4.4.6 of the EPA exposure assessment report , the following philosophy w as adopted in determining appropriate loading rates for different ty pes of P WPs in various structure ty pes – technically

the specific source (cabinets, countertop, paneling, etc.) of each P WP ty pe does not matter, as the model treats all sources in the same way; thus, for any loading scenario it is sufficient to determine and then sum all expos ed surface areas per P WP ty pe. F loor plans were used as a basis for developing the loadings . S preadsheets were developed to document the loadings of PWP components in items such as cabinets, doors and trim, and to then sum across like components to develop the resultant loadings for each of six PWP ty pes listed in the table above. The default loading rates differ for the new-home vs. renovation cases. For the renovation case, it was assumed that an entire kitchen was renovated, including cabinets, countertop and ancillary areas such as a pantry . It was further assumed that the vinyl covering the kitchen floor and adjacent hallway

floor was replaced with engineered wood. The interior doors, underlay ment and trim throughout the house were assumed to remain as before the renovation, as were P WPs in any areas beyond the kitchen other than the adjacent hallway f loor. **Table 2**  **- 7**  lists the FIAM - pwp default values for exposed surface area (in m2 ), for each of the six PWP ty pes listed above in each of the five default structure ty pes, for the case of new construction. **Table 2 -**  **8** lists the same information for the renovation case.20 **Tabl e**  **2 -**  **7. Default**  **Exposed Surface Areas (in m**  **2 )**  **for Six P** **WP Types, by Structure Type –**  **New -**  **home Case Structure**  **Type OSB/SWPW**  **Particleboar d**  **MDF Coated CWP**  **HWPW HWPW Laminate** 

**Zone Area**  **Zone Area**  **Zone Area**  **Zone Area**  **Zone Area**  **Zone Area**  **Apartment** 1 71.48 0 1 3.255 1 4.645 1 78.165 1 18.137 1 7.773 **Camper** 1 15.675 1 1.02 0 1 2.09 0 1 13.005 1 29.575 1 12.675 **Mobile Home** 1 98.47 8 1 3.90 6 1 4.366 1 65.78 6 1 26.6 10 1 11.404 **SF Attached Home**  1 71.645 1 1.39 0 1 2.175 1 52.91 0 1 6.2685 1 2.68 7

2 71.645 2 5.205 2 4.79 0 2 57.01 0 2 15.27 8 2 6.54 8 **SF Detached Home**  1 110.965 1 1.08 0 1 2.615 1 65.495 1 5.474 1 2.346

2 110.965 2 3.095 2 4.355 2 65.62 0 2 16.464 2 7.056 **Tabl e**  **2 -**  **8 .**  **Default Exposed Surface Areas (in m**  **2 )**  **for Six P** **WP Types, by Structure Type –**  **Renovation Case**  **Structure Type**  **OSB/SWPW Particleboard**  **MDF Coated CWP**  **HWPW HWPW Laminate** 

**Zone Area**  **Zone Area**  **Zone Area**  **Zone Area**  **Zone Area**  **Zone Area**  **Apartment** 1 0 1 3.255 1 4.645 1 39.775 1 15.365 1 6.585 **Camper** 1 0 1 1.02 0 1 2.09 0 1 4.47 0 1 17.017 1 7.293 **Mobile Home** 1 0 1 3.906 1 4.366 1 23.15 3 1 34.710 1 14.87 6 **SF Attached Home**  1 0 1 1.39 0 1 2.175 1 10.34 0 1 2.2 8 6 1 0.9 80

2 0 2 5.205 2 4.79 0 2 33.205 2 18.6 80 2 8.00 6 **SF Detached Home**  1 0 1 1.08 0 1 2.615 1 11.755 1 2.28 6 1 0.9 80

2 0 2 3.095 2 4.355 2 31.79 0 2 27.342 2 11.71821

**2. 4**  **Exposure Screen**  This screen (**Figure 2 -**  **8** ) enables the user to provide inputs related to the age of indoor sources and a formaldehyde level of interest (LOI) that is used in certain exposure calculations as well as activity p atterns (time spent in different locations or environments) for exposure groups (e.g., infants, workers, retires) and formaldehyde concentrations in environments outside the home. As with the House Screen, the inputs here can be divided into three screen portions: (1) Age of Sources and Formaldehyde LOI (upper portion); (2) Exposure Groups (middle portion); and (3) Concentrations Outside the Home (lower portion).

**Figure 2 -**  **8. Exposure Screen 2.4.1**  **Inputs and Options**  **for Age of Sources and Formaldehyde Level of Interest**  **Age of**  **Sources .**  The assumed age of indoor sources at the start of the exposure period (i.e., at the time when an individual moves into the modeled structure) affects the modeled indoor formaldehyde concentrations to which an individual is exposed

– in general, the lower the age of sources the higher the indoor concentrations at the start of the exposure period. With a source age of zero ye ars – the model default

– FIAM - pwp begin s exposure calculations with an initial indoor concentration in a newly constructed home, which is intended to reflect an equilibrium condition shortly (ty pically within 30 days) after a house has been loaded with PWPs . A source age of zero ye ars also would apply to new materials/furnishings added as part of a major remodeling effort. A model limitation here is that all sources are assumed to be the same age; FIAM - pwp does not allow different ages to be specified for different sources. **Upper Po**  **rtion**

**Lower Portion**  **Middle Portion** 22

**Formaldehyde Level of Interest (LOI)**  **.** One of the exposure calculations is the percent of time an individual is exposed to formaldehyde concentrations at or above some level of interest. By default, the LOIis set to 10 ppb ; this is easily changeable by entering a different value . **2.4.2 Inputs and Options**  **for Exposure Groups**  **Default Groups.**  As shown above in **Figure 2**  **- 8**  (middle portion), FIAM - pwp has six default exposure groups:  In fants (0 to < 2 ye ars of age)  Pre - school/school children (age 2 to < 16 ye ars of age)  Non- industry

workers (age 16 to <64)  Fabrication- industry

workers (age 16 to <64)  Retirees (age 64 or greater)  Part-time workers (age 16 to <64) The choice of age breaks to distinguish infants and pre - school/school children from adults was driven by t he possible age dependency o f cancer slope factors. EPA has developed age - dependent adjustment factors (ADAFs) 28 to address the potential for differential potency associated with exposure during early life (below 16 ye ars of age). There is a 10 - fold adjustment for ages 0 to <2 ye ars , a 3 - fold adjustment for ages 2 to <16 , and no adjustment for ages 16 and older. Workers were split into full -time and part-time sub groups; full -time workers were further divided to distinguish non- industry workers from wood- industry s egments where higher occupational formaldehyde exposures can occur. In terms of activity patterns, the retiree group also can be used to represent individuals of age 16 to <64 who are unemployed or working at home. A subset of the exposure groups can be selected for a model run by checking or un- checking the check-boxes on the left for each line. The default values for any group can be modified using the **Edit** button to the right ; the original/default values can be restored using the Restore button . As discussed below, user- defined exposure groups also can be added. The third column from the left on each line indicates whether the inputs for each exposure group are default (D) values, revisions (R) of defaults, or newly created (C). The inputs for exposure groups are annual hours spent at each of five locations or environments:  In z one 1 at home  In z one 2 at home  At work, school or daycare  In a vehicle  At all other locations The sum of the default hours at these locations is 8,760 , that is , the number of hours in one year ; if the edited values do not sum to 8,760, then FIAM - pwp displays the sum in red font to indicate that corrections are in order. For two - zone structures, Zone 1 is conceptualized as upstairs or the sleeping area and Zone 2 is conceptualized as downstairs or the living area. For one - zone structures the sleeping and living areas are grouped together in a single zone.

28 See, for example, http://www.epa.gov/oswer/riskassessment/sghandbook/chemicals.htm .23

**Custom G** **r oups.**  User- defined exposure groups can be added via the **Add** button, in the screen area below the listing of the default groups. **Fi gure**  **2 -**  **9** shows illustrative inputs, just before adding them. Inputs are the name of the group and the annual hours spent in each of the f ive locations/environments, along with the formaldehyde concentration at the work/school/daycare location (see further discussion below, in **Section 2.4.3**  ). The hours by l ocation should sum to 8,760; if not, after the exposure group has been added FIAM - pwp will assign a red font to Total Hours to indicate that some adjustments are in order. Once added, newly defined exposure groups can be later removed by the user. A maximum of three newly defined exposure groups can be added. For concentrations outside the home, the formaldehyde concentration at the work/school/daycare location can vary

b y exposure group. Thus, when a new exposure group is added the required inputs include not only the annual hours at each location but also the concentration at the work/school/daycare location.

**Figure 2 -**  **9 .**  **Preparing to Add a New Exposure Group 2.4.3**  **Inputs and Options for Concentrations**  **Outside the Home** Locations outside of, or away f rom, the home are included in FIAM - pwp to provide a total or “around-the - clock” exposure perspective. The concentration values assigned to these locations are displayed on the lower portion of the Exposure Screen (see **Figure 2**  **- 8**  on previous page). The default values shown in the figure can be modified by the user. The changes can be made in e ither the ppb or μg/m 3 column; FIAM - pwp will automatically convert in either direction using the relationship 1 ppb = 1 . 23 μg/m 3

. The model defaults can be restored at any time using the **Load Default**  button at the bottom of the screen.24

**2.4.4 Basis for**  **Defaults Exposure**  **Groups.** The 2009 Exposure Factors Handbook ( EFH ) update 29 (External Review Draft) was the primary

source of information on activity patterns, that is, how an individual’s time is allocated among residential and non- residential locations. E stimates of annual hours at home and non-home locations are provided for each exposure group in **Table 2 -**  **9** . The total time spent at home was determined from EFH tables that indicate the time spent at home in all rooms combined. The time at home in Zone 1 was defined as the sum of time spent in the bedroom or bathroom. EFH statistics indicate that infants spend, on the average across the population, one hour per day

at daycare facilities. Children of school age were assumed to spend 6.5 hours per day at schoo l, for 180 days per ye ar. Full -time workers were assumed to spend 8 hours per day at work, for 250 days per year. The hours at work or school for part-time workers and retirees were based on EFH statistics, as were the hours in a vehicle for each exposure group. The time spent in “all other” environments was determined by subtraction from the total time budget of 8,760 hours per year. **Table 2 -**  **9. Default Annual Hours at Home and Non -**  **home Locations, by Exposure Group. Exposure Group**  **Location**

**Home Zone 1**  **a Home** 

**Zone 2 Work or**  **School or Daycare**  **In**

**Vehicle All** 

**Other Total, all**  **Locations Infants**  4,958 1,652 365 252 1,533 8,760 **Pre -** **school/School** 4,253 1,292 1,170 356 1,689 8,760 **Non -** **industry Workers** 3,327 2,032 2,000 590 811 8,760 **Fabrication Work ers**  3,327 2,032 2,000 590 811 8,760 **Retirees** 3,607 3,538 107 372 1,136 8,760 **Part -**  **Time Workers** 3,935 2,038 1,000 401 1,386 8,760 a Zone 1

– upstairs (sleeping area); Zone 2

– downstairs (living area). **Concentrations Outside**  **the Home.**  Unlike the re sidential concentrations calculated by FIAM - pwp , which are decayed over time, these concentrations are treated as constant over time. The default concentrations (see **Table 2**  **- 10**  ) assigned to non-home locations, which assume a baseline emissions scenario, were derived from several sources. In-vehicle and outdoor/other concentrations were based on average values reported from EPA’s air monitoring network (see Section 3.1 of the formaldehyde exposure assessment report). The value assigned to vehicles (6 ppb) is the average reported for the “mobile” land use category ; the value assigned to outdoors/other (3 ppb) is the average of values reported for “residential” and “commercial” land use categories, with consideration also given to outdoor formaldehyde levels me asured in residential monitoring studies. The value assigned to the fabrication- industry workplace was taken from EPA ’s occupational exposure assessment for formaldehyde 30

. The values assigned to daycares, schools and non- industry workplaces involved calcul ations that are described below.

29 http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=209866 30 USEPA. 2011. Draft Final. Assessment of Occupational Exposure to Formaldehyde from Composite Wood Products. U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics, Chemical Engineering Branch, 1200 Pennsylvania Avenue NW, Washington, DC 20460 . 6 October 2011.25 **Table 2**  **- 10**  **. Default**  **Concentration Values for Non -**  **home Locations**

**Location Formaldehyde**  **Concentration pp** **b μ** **g/m 3**  Dayc are 9.8 12.0 School 8.7 10.7 Work, Non- Industry 10.0 12.3 Work, Fabrication 199.5 244.9 Vehicle 6.0 7 .4 Outdoors/Other 3.0 3.7 In developing the baseline concentrations for daycare, school and non- industry work locations, it was assumed that 10 percent 31 of the buildings in each category were of recent construction or were recently renovated. As with the fabrication- industry workplace, the value for newer buildings associated with the non - industry workplace was taken from the EPA ’s 2011 Assessment of Occupational Exposure to Formaldehyde from Composite Wo od Products report referenced above. Newer schools were assigned the 95 th percentile formaldehyde concentration, thought to represent newer or recently renovated buildings, from a relatively large monitoring study32 of portable and traditional classrooms in California schools . The value assigned to newer daycare facilities is an average of the concentration for non- industry work and averages from field studies 33 , 34 of newer homes. For older daycare, school and non- industry buildings, the 25 th percentile for formaldehyde levels measured in the EPA BASE 35 study was used. **Table 2**  **- 11**  shows the derivation of the age - weighted baseline concentration values for these building types.

31 The most recent DOE/EIA Commercial Building Energy Consumption Survey (CBECS) indicated that about 5 % of office buildings and 8 % of education buildings were of recent construction (i.e., 3 years old or less); see http://www.eia.gov/emeu/cbecs/cbecs2003/detailed_tables_2003/detailed_tables_2003.html , Table B - 8 . 32 CARB. 2004. Environmental Health Conditions in California’s Portable Classrooms . Report to the California Legislature by

the California Air Resources Board (CARB) and the California Department of Health Services, November 2004. Available at: http://www.arb.ca.gov/research/apr/reports/l3006.pdf . 33 F. J. Offermann, J. Robertson, D. Springer, S. Brennan, and T. Woo. 2008. Window U sage, Ventilation, and Formaldehyde Concentrations in New C alifornia Homes: Summer Field Sessions. ASHRAE IAQ 2007 Conference , Baltimore, MD. 34 A.T Hodgson, A.F. Rudd, D. Beal, and S. Chandra. 2000. Volatile Organic Com pound Concentrations and Emission Rates in New Manufactured and Site -Built Houses. Indoor Air 10 : 178 - 192. 35 http://www.epa.gov/iaq/base/26

**Table 2**  **- 11**  **. Derivation of Baseline Values for Daycare, School and Work Locations**

**Location Formaldehyde**  **Concentration , ppb** 

**Older Buildin** **gs Newer** 

**Buildings Composite**  **a of** 

**Older & Newer** Dayc are 7.0 35.0 9.8 School 7.0 24.0 8.7 Work, Non- Industry 7.0 36.5 10.0 a Com posite value = 90 % x (value for older buildings) + 10 % x (value for newer buildings ). The values for vehicle and outdoor/other concentrations are assumed to be the same for different analytical options (baseline, CARB1, etc.) whereas those for the other locations can vary (see **Table 2**  **- 12**  ), because the formaldehyde concentrations in the fabrication workplace , as well as newer/renovated daycares, schools and non- industry workplaces , could be affected by a new rule for formaldehyde. As with the baseline values, suggested concentration values for other analytical options for newer non- industry workplaces were taken from the recent EPA report referenced above. For daycare facilities , the percent reductions across analy tical options used for fabrication and non- industry

work were applied. A similar approach was used for schools, except that the percent reductions were lowere d slightly (i.e., by 1 0 percent) to account for generally higher prevailing air exchange rates in schools, which would tend to temper the effect of formaldehyde emission reductions. **Table 2**  **- 12**  **. Concentration Values for Selected Non -**  **home Locations, by Emi ssions Scenario**  **Location Formaldehyde**  **Concentration , ppb** 

**Baseline a**  **CARB1 CARB2**  **NAF** Dayc are b 9.8 9.5 9.4 8.0 School b 8.7 8.1 8.0 7.3 Work, Non- Industry b 10.0 9.4 9.3 7.9 Work, Fabrication 199.5 192.0 190.8 93.0 a FIAM - pwp provides baseline values as the defaults for non-home locations. b The values assigned to these locations are a weighted average of those for older and newer buildings ; see text . In c alculating total exposure for the exposure groups, FIAM - pwp combines the time spent in various locations with concentrations encountered at those locations. For the work/school/daycare location , FIAM

- pwp uses the daycare concentration for infants, the school concentration for children, and the work concentration for workers and retirees. When a new exposure group is added (see **Figure 2**  **- 9**  above), in addition to the time spent at each location the user also needs to enter an appropriate value for the concentration at the work/school/daycare location.27

**2. 5**  **Result Screen** This screen (**Figure 2**  **- 10**  ) lists modeled indoor formaldehyde concentrations (upper portion of the screen) together with exposure estimates (lower portion) . Further details are provided below.

**Figure 2 -**  **10 .**  **Result Screen**  **with F** **irst T** **wo E**  **xposure G** **roups S**  **elected 2.5.1**  **Co n**  **centration Result s**  FIAM - pwp lists the concentrations calculated for Zone s 1 and 2 under the temperature and humidity conditions entered by

the user; the Zone 2 results are set to the background concentration if the user has specified a one - zone structure. **Section 3.**  **9** describes the procedures and gives the equations that are used to adjust modeled concentrations to the user- specified conditions. Concentrations are reported both in volume/volume (ppb ) and mass/volume ( μ g/m3 ) units. Initial concentrations

– those listed for 0 months under Time from Initial Concentration

– reflect the condition shortly after a house has been loaded with PWPs . As described in **Section 3.**  **7** , estimates of initial indoor concentrations due to PWPs are decayed exponential ly by the model, in accordance with a user- specified emissions half life (default of 1.5 years), to develop estimates for subsequent points in time. Results are provided for time points that are 3 months, 6 months and 12 months later than that for the initial concentration values, plus a user- specified point in time (24 months by

default). The user- specified value for length of time over which to decay the initial concentration is entered on the House Screen, where the default emissions half life also can b e changed. **Upper Po**  **rtion**

**Lower Portion** 28

The results also include the time required for the highest initial indoor concentration to drop below a user- specified concentration (an input on the House Screen). The equation used for this calculation is given in **Section 3. 7**  . By definition, the indoor concentration cannot decay to a value that is lower than the background concentration (an input on the House Screen). If the value to which the indoor concentration is to be decayed is less than or equal to the background concentration, then the calculation result is undefined. In such cases, FIAM - pwp reports 0 months as the time to decay . As described in greater detail in **Section 3**  , the model calculates the initial indoor concentration(s) under an assumed steady- state condition. In real life, a true steady- state is never achieved, due to the dy namics of formaldehyde source emissions and indoor sinks. Formaldehyde sources ty pically do not emit at a constant rate, but rather at a rate that tends to decline over time as the “reservoir” of initial f

ree formaldehyde, coupled with that formed through hydrolys is, is gradually depleted. Although a true steady- state is never reached, it has been observed in field studies that the combined actions of sources and sinks will result in an initial rise in the indoor concentration, followed by

a “ leveling off” period that may b e fairly brief and then a longer period of gradual decline in concentration. The initial “steady- state ” concentrations estimated by FIAM - pwp are intended to approximate the indoor concentrations during the leveling- off period, which ty pically would occur within 30 days or less following the installation of PWPs. **2.5.2 Exposure Results**  An average daily

c oncentration (ADC) is reported for each zone of the house, or other modeled structure, and for each default or added exposure group selected by the user. The percent of time during which the concentration in each zone is greater than a user- specified level of interest (LOI) is also reported. For each exposure metric, annual averages are reported for the first modeled ye ar and for the next ten years thereafter. ADC calculations for exposure groups are based on time spent, and concentrations encountered, in the two zones of the house together with times and concentrations when the individual is out of the house. Concentrations in the house are calculated by t he model and decay over time, whereas out- of -house concentration s are input by the user on the Exposure Screen and are assumed to be constant over time. Further details on exposure calculations, including equations, are provided in **Section 3. 10**  . **2.5.3 Printing Inputs and**  **Result s**  An option at the top of the Result Screen

– **Generate pdf**

– enables the user to create a pdf file that contains both the inputs and results for a model run. The pdf mimics the appearance of the input screens and creates a table listing the same model outputs as shown on the Result Screen. **2.5.4 Archiving Inputs and Results for a Run**  Another option at the top of the Result Screen

– **Download Excel** 

– enables the user to save a file in Excel format that contains all inputs and results for the current model run. The saved Excel file has three sheets or tabs, named Combined, Inputs and Results. FIAM - pwp creates an Excel file for each run name; if multiple runs are made under the same run name and the download button is pressed after each run , then FIAM - pwp will append each set of inputs and results to the Excel file . The Inputs sheet has one column for each input and creates one Excel row for each model run. The Results sheet has columns for each output and creates 11 rows for each model run, because ADC results are provided for Zone 1, Zone 2, and exposure groups for each of 11 ye ars (year 0 - 1, ye ar 1 - 2, etc.). FIAM

- pwp concentration results, which relate to single points in time, are duplicated across the 11 rows. Similarly, the Combined sheet containing inputs and results has 11 rows and duplicates both the inputs and the modeled concentrations across the 11 rows that are generated for each run.29

**2. 6**  **Model Access and Addition**  **al Features 2.6.1**  **Accessing the IGEMS Webs** **ite** The IGEMS website that houses FIAM - pwp can be accessed at https://ofmpub.epa.gov/igems - jsp/ . After the Privacy

A ct Notification has been acknowledg ed, a user c an l og in if he/she has an account ( otherwise set up a new account) . After logging in, a user can access FIAM - pwp by selecting it benath **Formaldehyde Indoor Air Model** from the choices to the left. **2.6.2 Saving Inputs for Later Access**  The first time FIAM

- pwp is us ed , the Run FIAM button at the bottom will not be available until inputs have been provided or choices have been made on the House Screen, Source Screen and Exposure Screen . When the run button is pressed , FIAM - pwp will prompt for a Run File Name. Up to 20 characters can be used in naming the file. After the SAVE button is pressed , FIAM - pwp will show the Result Screen. A new run file can be created, or a current one saved, at any time

– creating, opening and saving run files works much like similar functions in Microsoft Windows. Once a run file has been named and saved, it will be included on the list that can be accessed by pressing the Open File button. If the SAVE button is pressed using a file name that already exists, FIAM - pwp will ask whether the existing run file should be overwritten. **2.6. 3**  **Context**

**- sensitive Help**  FIAM - pwp provides context- sensitive help via a series of buttons with a “ **?** ” icon. When the icon is pressed a dialog box appears with help specific to the input or option with whi ch it is associated. Pressing the **Close** button returns the user to the input or output screen. There is also an **Overview** button for each of the input screens that ; when this button is pressed FIAM - pwp displays a brief description of the purpose of the scre en and the ty pes of inputs required. All of the help dialogs provided by FIAM

- pwp can be saved by

pressing the **Save FIAM**  **Help** button that is accessed on the Result Screen. **2.7 Example Applications**  Six examples are provided in this section to illustrate certain FIAM - pwp features and options as well as the insights that can be obtained from making model runs, particularly a series of related runs. **2.7.1 Example 1**  **– Modeling**  **with Model Default Values** This example illustrates how FIAM - pwp results can be obtained quickly when using default values for items such as ty

pe of structure, climate zone, indoor sources, and exposure groups. As described in previous sections, the default values reflect decisions or choices made in the EPA 2012 formaldehyde exposure as sessment (see footnote 10 in **Section 1**  ). The example further illustrates how minor changes from the defaults can be made to view complementary results. The key choices for this example are indicated in the run notes provided in **Table 2**  **- 13**  for Part 1 . First, on the H ouse Screen, Apartment (a one - zone structure) was selected as the structure ty pe and Zone 5 was selected as the climate zone. Second, default PWP ty pes were loaded on the source screen with the choices of baseline emissions and new construction (as opposed to renovation). Third, default exposure groups were chosen on the Exposure Screen. Model defaults were used for all other inputs not mentioned above. The modeling results indicated an initial indoor formaldehyde concentration of 78.6 ppb .30 **Tabl e**  **2 -**  **13 .**  **Run Notes for Example**  **1 Screen**  **Notes Part 1**  House Select **Apartment** and Climate Zone 5; defaults otherwise Source Select "Add D efault PWP Types" with Emission C lass = **baseline** , Case =

**new -**  **home** (six sources will appear, all checked) Exposure Sele ct default exposure groups (no action needed; all checked by default) Result Initial concentration

– 78.6 ppb ( 97.1 μg/m 3 ) for Zone 1, N/A for Zone 2 **Part 2**  House Keep **Apartment** and Climate Zone 5 Source Select "Add Default PWP Ty pes" with Emission Class = **CARB2** , Case = **new -**  **home** (Note : clear previous list before adding new sources) Result Initial concentration

– 68.5 ppb ( 84.6 μg/m 3 ) for Zone 1, N/A for Zone 2 **Part 3**  House Keep **Apartment** and Climate Zone 5 ; change air exchange rate to **0.4 ACH**

by changing flows to and from outside from 52.26 to 104.52 m3 /h Source Select default PWP ty pes – Emission Class = **baseline** , Case = **renovation** (Note: clear previous list before adding new sources) Result Initial concentration

– 49.0 ppb ( 60.5 μg/m 3 ) for Zone 1 , N/A for Zone 2 **Part 4** House Select **SF Detached** ; keep Climate Zone 5 Source Program will issue a warning due to change in structure type; click OK.

Select default PWP ty

pes – Emission Class = **baseline** , Case = **new -**  **home** (Note: clear previous list before adding new sources ; 12 sources will appear) Result Initial concentration

– 57.1 ppb ( 70.5 μg/m 3 ) for Zone 1,

59.9 ppb ( 74.0 μg/m 3 ) for Zone 2 Next (see Part 2), the emission class was changed to CARB2, which has lower emissions than baseline. All other inputs were kept the same as for Part 1. The modeled initial concentration in this case was 68.5 ppb . Then (Part 3) the emission class was changed back to baseline while choosing the loading rates for renovation instead of new construction and changing the air exchange rate from 0.2 to 0.4 ACH, by doubling the airflow rates to/from outdoors; the modeled initial concentration in this case was 49.0 ppb . Last (Part 4) , baseline emissions and new construction were chosen while changing the structure ty pe to S F detached (a two - zone structure). The initial modeling results in this case were 57.1 ppb for Zone 1 (sleeping area) and 59.9 ppb for Zone 2 (living area). **2.7. 2**  **Example 2**  **– Modeling a Hypothetical Chamber Test for CARB Compliance**  This example is drawn from the 2012 EPA exposure assessment report previously cited in **Section 1.** ASTM E1333 - 10, Standard Test Method for Determining Formaldehyde Concentrations in Air and Emission Rates from Wood Products Using a Large Chamber (ASTM 2010), is commonly used to demonstrate compliance with formaldehyde emission standards. The method prescribes an air exchange rate for testing of 0.5/hr and product loading ratios of 0.43 m2/m3 for PB , 0.95 m2/m3 for HWPW, and 0.26 m2/m3 for MDF. Using these rates and an assumed slope , the intercept can be determined for a hy

pothetical source that just meets a given emissions standard. The CARB231

emission standard for MDF is 0.11 ppm (110 ppb) or 0.135 mg/m 3

. Per the 2012 EPA exposure assessment, a MDF specimen complying with the standard would have an intercept value of 0.40 mg/m2

-hr, assuming a slope of 1.06 m/hr based on historical chamber tests of MDF specimens. FIAM - pwp was used to model a hy pothetical chamber test with an MDF specimen that just meets the standard (see notes for this example in **Table 2**  **- 1**  **4** ) . An assumed air exchange rate of 0.5/hr and chamber volume of 100 m 3 equates to an airflow rate of 50 m 3 /hr into and out of the chamber . The volume assumed does not matter, as the exposed surface area scales to the volume via the loading ratio

– with a volume of 100 m 3 the corresponding MDF surface area is 26 m2

. The assumed slope was 1.06 m/hr, the average value from ~ 30 historical tests of various MDF specimens (see **Appendix D**  of this report) . The modeling result

– an initial concentration of 108.5 ppb

– confirms compliance of the hypothetical MDF specimen with the standard (110 ppb) . **Table 2**  **- 1**  **4 .**  **Run Notes for Example**  **2 Screen**  **Notes** House Use “Add Your Own Structure Ty pe” to create new ty

pe named Chamber Zone 1 (Chamber)

– volume = 100.0 m 3 ; flow to/from outside = 5 0.0 m 3 /hr Check box next to “Check here if one - zone case” Create climate zone named Standard Conditions, 23 °C and 50 % RH Change b ackground concentration to 0.0 ppb Source Add custom values for PWP ty pe MDF, Emission Class Meet CARB2 110 ppb Area = 26.0 m2 , Slope = 1.06 m/hr; Intercept = 0.4 mg/m2

-hr Exposure No exposure group selected (uncheck all) Result Initial concentration = 108.5 ppb (134.1 μg/m3 ) **2.7. 3**  **Example 3**  **– Demonstrating an Equilibrium Concentration**  The default MDF source in FIAM - pwp has a baseline emission rate characterized by an intercept of 0.28122 mg/m2

-hr and a slope of 1.06 m/hr. The formaldehyde equilibrium concentration, obtained by

dividing the intercept by the slope , is 0.2653 mg/m3 or 265 .3 μg/m 3

. Attainment of an equilibrium concentration can be demonstrated via modeling. FIAM - pwp was run with a hy pothetical chamber volume of 100 m 3 and an airflow rate of 50 m 3 /hr, as in the previous example. An arbitrarily large exposed surface area of 1 00,000 m 3 was assumed. The modeled concentration in the chamber (265.2 μg/m 3 ; see run notes in **Table 2**  **- 1**  **5** ) is consistent with the calculated value for the equilibrium concentration. **Table 2**  **- 1**  **5 .**  **Run Notes for Example**  **3 Screen**  **Notes** House Use created structure typ e named Chamber

Zone 1 (Chamber)

– volume = 100.0 m3 ; flow to/from outside = 50.0 m3 /hr Check box next to “Check here if one - zone case” Use created climate zone named Standard Conditions, 23 °C and 50 % RH Change b ackground concentration to 0.0 ppb Source Add PWP ty pe MDF, Emission Class = baseline, Case = new-home Area = 100,000 m2 , Slope = 1.06 m/hr; Intercept = 0.28122 mg/m2

-hr Exposure No exposure group selected (uncheck all) Result Initial concentration = 214.6 ppb (265.2 μg/m3 )32

**2.7. 4**  **Examp le**  **4 –**  **Examining the Incremental Contribution of a Product** As described in **Section 2.1**  , a prior online version of FIAM - pwp (v1.0) was subjected to a peer review. In commenting on the backpressure effect, one of the reviewers noted the following: Assessment of acute/chronic exposure is associated with different uncertainties and conceptual models. In the acute setting, the back pressure effect may attenuate the contribution of a new product such that the total acute indoor exposure concentration is not affected. However, in a chronic or long- term timeframe, it is reasonable to expect that the majority of available formaldehyde and precursors ultimately will partition from the product into the indoor space. My recommendation is that a conceptual framework be developed or documented to ensure that users take these factors into consideration when investigating acute versus chronic timeframes. For the acute timeframe, it is important to consider the total collection of assembled indoor products. For chronic exposure, a more accurate characterization of dose attributable to a single product is likely obtained by considering the decay profile of that product in the absence of other products; the attenuation due to the backpressure effect is temporary and, eventually, a source that is initially attenuated will begin to emit formaldehyde as the indoor- air concentration decreases. To illustrate some of the reviewer’s points , the incremental contributions of illustrative CWPs were examined by

modeling them both as a single source and in the presence of other CWPs . As shown in **Fi gure**  **2 -**  **1 1**  , FIAM - pwp has loadings of six default PWP ty pes for apartments; these were used in a series of model runs with an apartment as the structure ty pes (see run notes in **Table 2**  **- 1**  **6**). For thes e runs, the background concentration was set to 0 .0 ppb.

**Figure 2 -**  **1 1**  **. Emission -**  **rate P arameters for**  **FIAM -**  **pwp Default PWPs in an Apartment.**  For the first run, only MDF was selected (by checking the corresponding check-box), resulting in a modeled initial concentration of 23.4 ppb. Next, the model was run checking all sources except MDF, with a resultant modeled initial concentration of 70.7 ppb. The modeled initial concentration when all sources , including MDF, were selected was 77.3 ppb

– less than the sum of results from the first two runs and , thus, illustrating the suppression of emissions in the presence of other sources. A similar series of runs was made with OSB/SWPW as the focus. The modeled concentration for OSB/SWPW only

was 22.9 ppb

– similar to that for MDF, but with an exposed surface area about 15 times as large . The modeled concentration with all sources except OSB/SWPW ( 88.3) ppb ) was higher than that obtained with all sources, including OSB/SWPW ( 77.3 ppb). This outcome illustrates that OSB/SWPW acts as a “net absorber” in the presence of the other default PWP ty pes used in the example. The relative emission s strength of each PWP ty pe is apparent from its equilibrium conc entration, which for MDF is more than five times that of OSB/SWPW (equi librium concentrations are listed in **Figure 2 -**  **11** ) .33 **Table 2**  **- 1**  **6 .**  **Run Notes for Example 4**  **Screen Notes**  **Part 1** House Select Apartment and Climate Zone 5; background = 0; defaults otherwise Source Select default PWP ty pes – Emission C lass = baseline, Case = new -home **Check only the MDF type** Exposure No exposure group selected (uncheck all) Result Initial concentration

– 23.4 ppb (28.9 μg/m3 ) **Part 2**  House Keep Apartment, Climate Zone 5, and background = 0 Source Keep default PWP ty pes – Emission C lass = b aseline, Case = new-home **Check all PWP**  **type s except MDF**  Result Initial concentration

– 70.7 ppb (87.4 μg/m3 ) **Part 3**  House Keep Apartment, Climate Zone 5, and background = 0 Source Keep default PWP ty pes – Emission C lass = baseline, Case = new-home **Chec k**  **all PWP type**  **s, including MDF** Result Initial concentration

– 77.3 ppb (95.5 μg/m3 ) **Part 4**  House Keep Apartment , Climate Zone 5 , and background = 0 Source Keep default PWP ty pes – Emission C lass = baseline, Case = new-home **Check only the OSB/SWPW t** **ype** Result Initial concentration

– 22.9 ppb (28.3 μg/m3 ) **Part 5**  House Keep Apartment and Climate Zone 5 Source Keep default PWP ty pes – Emission C lass = baseline, Case = new-home **Check all PWP**  **type s except OSB/SWPW**  Result Initial concentration

– 88.3 ppb (109.0 μg/m3 ) **2.7. 5**  **Example 5**  **– Varying the Decay Rate (Half Life)**  As discussed later in this report (see **Section 3.5**  ), several peer reviewers suggested multiple or changing decay

rates to represent, for example, “fast” (earlier) and “slow” (later) peri ods of exponentially

declining formaldehyde emissions. Such an undertaking , although a “ stretch” of FIAM - pwp ’s capabilities, is possible provided that adequate care is taken. The key to varying the decay rate is having a means to predict the initial concentration for the point in time at which this rate i s changed. For this example it was assumed that the fast decay could be represented by a half life of one ye ar and the slow decay

b y a half life of three years. The fast- decay period was assumed to last one ye ar, followed by a slow- decay p eriod of nine ye ars. The resultant indoor- concentration time series over the 10 ye ars, calculated externally from the model, is shown in **Figure 2**  **- 12**  together with the default background concentration (7.5 ppb) that was assumed for the example . The change in the decay

rate can be seen as the “kink” in the time series at an elapsed time of one year.34

**Figure 2**  **- 12**  **. Formaldehyde Concentration Decline with Fast and Slow Decay Periods.**  Inputs for the example were simplified by assuming a single emitter

– MDF. For t he first run (Part 1; see **Table 2**  **- 17** ) , a half life of 1.0 ye ars was assumed together with an MDF exposed surface area of 18.5 m2 ; the modeled initial concentration was 63.7 ppb and the modele d concentration after one year was 35.6 ppb. For the second run (Part 2; see **Table 2**  **- 18**  ), the assumed half life was changed to 3.0 ye ars . For this run it also was necessary to adjust the source inputs such that the modeled initial concentration would be 35 .6 ppb. Through trial and error it was determined that this outcome could be obtained by changing the intercept for the MDF emission rate from the default value of 0.28122 to 0.1455 mg/m2

-hr . The modeled initial concentration in this case was 35.6 ppb and the modeled concentration after 108 months (9 ye ars, or 10 years cumulative) was 11.0 ppb. The collective results from the two runs are consistent with the time series in **Figure 2 -**  **12** .

**Table 2**  **- 1**  **7 .**  **Run Notes for Example**  **5 , Part 1 (fast decay period)**  **Screen N**  **otes** House Select Apartment as the structure type

Use created climate zone named Standard Conditions, 23 °C and 50 % RH Half life = **1.0 years**  Source MDF/baseline/new-home with surface area = **18. 3**  **5 m 2**  and default values for

slope/intercept (add only this ty pe with default surface area; edit surface area) Result Initial concentration = 63.7 ppb ( 78.7 μg/m 3 )

Conc entration at 12 months = 35.6 ppb (44.0 μg/m 3 ) **Table 2**  **- 18**  **. Run**  **Notes for Example 5**  **, Part 2 (slow decay period) Screen**  **Notes** House Change half lif e to **3.0 years**  Change time from initial concentration to **108 months**  (to get to 10 years) Source Change intercept for MDF to **0.1455 mg** **/ m** **2 -**  **hr** (by editing) Result Initial concentration = 35.6 ppb (44.0 μg/m3 )

Concentration at 108 months = 11.0 ppb ( 13.6 μg/m 3 )

Fast Decay Slow Decay35



### 3. **MODEL CALCULATIONS AND ASSUMPTIONS** This section describes the technical basis for the calculation routines in the software, which consist of two major components. The first of these predicts the initial “steady- state” formaldehyde concentration(s ) in one or two zones of the house due to the combined actions of sources and sinks in a newly

c onstructed home. The primary input for this component is an empirical emission-rate algorithm (i.e., estimated initial emission rate as a function of formaldehyde concentration and other environmental variables) for various ty pes of pressed-wood products. For more information regarding formaldehyde emissions from pressed-wood products, the reader is referred to an EPA report . 36 The second component of the model i s a decay function that gradually reduces the estimated initial steady- state concentration(s) due to indoor sources and sinks over a specified period of time. The concentrations are reduced in accordance with an exponential decay function, using a decay rate that is determined from a user input for the formaldehyde emissions half life. With this function, the concentrations at any point in the “life” of a home can be predicted, on the assumption that the materials in the house do not change over time and the air exchange rate, indoor temperature and indoor humidity

also remain constant. The first model component is based on the fundamental principle of conservation of mass in an indoor environment, as described in **Section 3.1**  . Amodel (see **Section 3.2** ) was developed during the 1980s to predict the formaldehyde concentration in a single indoor compartment under an assumed steady- state condition, taking into account the dependence of formaldehyde emission rates on the prevailing indoor concentration. This mode l has been extended (see **Section 3.**  **3** ) to predict formaldehyde concentrations in two indoor compartments under the same assumption. Whether a one - chamber or two - chamber model is used in the calculations depends on the ty pe of structure selected b y the model user (see **Section 2.2** ). An alternative formulation of the model, with an embedded calculation of the equilibrium concentration, is described and discussed in **Section 3.4**  . Other potentially useful modeling constructs are presented and discussed in **Section 3.5**  . Although the model , as currently formulated, technically

has the capability to represent indoor sinks, this model feature has been dropped due to several uncertainties together with the lack of supporting data. Some discussion of this topic is provided in **Section 3. 6**  . **Section 3.**  **7** describes the basis for the equation used to decay the initial steady- state concentration(s) over time and provides examples to illustrate calculations for concentrations at any point in time and for the time to reach a pre - defined concentration such as 10 ppb . **Section 3. 8**  documents the basis for selection of a default value for the formaldehyde concentration half life, which is needed to decay the concentration over time. **Section 3.**  **9** describes the equations used to adjust indoor formaldehyde concentrations calculated by the model, under baseline indoor conditions of 23  C and 50 % relative humidity, to the user’s inputs for temperature and humidity conditions. **Section 3. 10**  describes the exposure calculations used in the mode l.

36 US EPA . 1996. Sources and Factors Affecting Indoor Emissions from Engineered Wood Products: Summary and Evaluation of Current Literature . EPA- 600/R- 96 - 067, NTIS PB96 - 1 83876, June 1996. Project Summary is available at: http://nepis.epa.gov/Adobe/PDF/P1000I7X.PDF .36

**3.1 Generalized Mass**  **- Balance Equation**  The formaldehyde concentration in an indoor environment is dependent on two ty pes of factors: (1) those that increase the concentration, such as emissions from formaldehyde sources, and (2) those that decrease the concentration, such as dilution with outdoor air assumed to be lower in concentration than that indoors. Although the two ty pes of factors would appear to be distinct entities, they

actually are interdependent because of formaldehyde’s general behavior

– emission rates from pressed-wood products are dependent on the concentration in the indoor volume, and the formaldehyde concentration, in turn, is dependent on these emission rates as well as removal mechanisms . The principle of conservation of mass in an indoor environment is fundamental to the formaldehyde modeling process. Simply stated, this principle means that the rate of change over time in the formaldehyde mass indoors is determined by the rates of generation and removal. This principle can be expressed mathematically for an indoor compartment or zone as follows:



##    

   



     i Zone in sinks num p p i i Zone in sources num k k

i i jj i ij i jj j ji i i i i i S E C Q C Q C Q C Q dt dC V 1 , 1 , 0 0 0 (Eqn. 3 - 1) where: V = indoor volume (m3 ) C = formaldehyde concentration (mg/m3 ) t = time (hr) i, j = indoor compartments ( 0 signifies the outdoors) Q = airflow rate between indoor zones or between indoor zone and outdoors (m3 /hr) Ei,k = emission rate for formaldehyde source k in zone i (mg/hr) S i,p = sorption rate for formaldehyde absorbent p in zone i (mg/hr). Model results are presented in both volume/volume units (ppb) and mass/volume units (μg/m 3 ). Conversion between these unit conventions is performed using the ideal gas law, assuming constant pressure (1 atmosphere) and the user- specified temperature.37

**3.2 Steady** **- State Model for Initial Formaldehyde Concentrati** **on in One Compartment** A model developed in the 1980s by Matthews and colleagues was designed to estimate the steadystate formaldehyde concentration resulting from emission sources in a single indoor compartment. The following discussion is in large part excerpted from Matthews et al. 37 The underlying model theory and its derivation are described in the same document and in a paper by Matthews et al . 38 At steady state, the formaldehyde (CH2 O) concentration in a single compartment can be expressed as follows: [CH 2 O] SS = [CH

2 O] out + CH

2 OER/(F * ACH * VOL) (Eqn. 3 - 2) where:[CH

2 O] SS = steady- state formaldehyd e concentration inside the compartment

(mg/m3 ) [CH 2 O] out = formaldehyde concentration outside the compartment (mg/m3 ) ,

assumed to be constant over time CH 2 O ER = emission rate of a formaldehyde source inside the compartment (mg/h) F = fraction of air coming into the compartment that mixes within

the volume (i.e., the mixing factor) ACH = air exchange rate with outdoors for the compartment (hr- 1 ) VOL = volume o f the compartment (m3 ). Assuming that F is equal to unity and using Q (airflow rate into and out of the compartment, in m 3 /hr) to denote the product of ACH * VOL, Equation 3 - 2 becomes: [CH 2 O] SS = [CH

2 O] out + CH

2 OER/Q (Eqn. 3 - 3) Application of the model as expressed in Equation 3 - 3 is simplified by assuming that all parameters in the equation remain constant (at steady state) and that there are no permanent losses of formaldehyde due to irreversible sorption to sinks. Emissions from pressed- wood sources are area- dependent in that the magnitude of the emission is a direct function of the surface area ( Area ) of the source in the compartment. The equivalent of Equation 3 - 3 for an area- dependent source is: [CH 2 O] SS = [CH

2 O] out + (CH

2 OER  * Area)/

Q (Eqn. 3 - 4) with CH

2 OER  in units of mg/m2

-hr and A rea in m2

.

37 T. Matthews, T. Reed, B. Tromberg, C. Daffron, and A. Hawthorne. 1983. Formaldehyde Emissions fro m Com bustion Sources and Solid Formaldehyde Resin Containing Products: P otential Im pact on Indoor Formaldehyde Concentration and Possible Corrective Measures. In Proceedings of ASHRAE Symposium “Management of Atmospheres in Tightly Enclosed Spaces ,” Santa Barbara, CA. 38 T. Matthews, A. Hawthorne, C. Daffron, T. Reed, and M. Corey. 1983b. Formaldehyde Release from Wood Products. In Proceedings of the 17th International Particleboard Symposium , Washington State University, Pullman, WA.38

The formaldehyde emission rate, CH 2 OER  , is formulated consistent with a one - dimensional representation of Fick’s Law 39 , describing the emission rate as the rel ease rate when the formaldehyde air concentration is zero, reduced by the product of the mass transfer coefficient and the vapor-phase concentration . This formulation can be expressed as follows: CH 2 OER  = -m * [CH 2 O] V + b (Eqn. 3 - 5) where: m = the mass transfer coefficient (m/hr) [CH 2 O] V = the CH2 O concentration in the vapor phase (mg/m3 ) b = a constant; the emission rate at zero CH2 O concentration in

the air (mg/m2

-hr). As noted by

Matthews, Hawthorne and Thompson (see footnote on this page ): Thus, the modeled CH 2 O emission rates maximize at zero CH 2 O concentration and decrease linearly to a net emission rate of zero at some equilibrium CH 2 O concentration. If the CH 2 O concentration is raised beyond the equilibrium level with the addition of new CH 2 O sources, extrapolation of the model to higher CH 2 O concentrations indicates that sorption of the CH 2 O by the original ‘emitter’ is expected to occur. Experimental results of individual and paired emitters in small-scale environmental chambers by Pickrel et al. 40 and Godish et al. 41 are consistent with this theory. Paired source contributions of pressed - wood products, insulation, carpeting and UFFI typically yielded CH 2 O concentrations less than the sum of the concentrations for the individual emitters. In addition, Godish found that the CH 2 O emission strength of many weaker emitters in paired source combinations was enhanced following brief exposure to a stronger emitter. This suggests a temporary sorptive mechanism for CH 2 O followed by reemission of CH 2 O at reduced CH 2 O concentrations. The vapor-phase concentration, [CH 2 O] V , by definition is equal to [CH 2 O] SS at steady

state; therefore, substitution of [CH 2 O] SS and Equation 3 - 5 into Equation 3 - 4 results in the following expression: 

##    

Q Area m O CH Q Area b O CH out

SS * 1 * 2 2    (Eqn. 3 - 6) In the case of multiple pressed-wood sources , Equation 3 - 4 becomes: [CH 2 O] SS = [CH

2 O] out + 

(CH 2 OER  k * Area k ) / Q (Eqn. 3 - 7) where the subscript k refers to the k th source. By

extension, Equation 3 - 6 then becomes: 

##     

##  

  QArea m O CH Q Area b O CH k k k out k k k

SS 

##  

   * 1 * 2 2 (Eqn. 3 - 8 )

39 T. Matthews, A. Hawthorne, and C. Thom pson. 1 987. Formaldehyde Sorption and Desorption Characteristics of Gy psum Wallboard. Environmental Science &Technology 21: 629 - 634. 40 J. Pickrel, L. Griffis, B. Mokier, G. Kanapilly, and C. Hobbs. 1984. Formaldehyde Release Rate Coe fficients from Selected Consumer Products. Environmental Science &Technology 18 : 682 - 6 86 . 41 T. Godish and B. Kanyar. 1985. Formaldehyde Source Interaction Studies. Forest Products Journal 35: 13 - 17.39

**3. 3**  **Extension of the Steady -**  **State Model to Two Com partments**  The formulation for the single - compartment case is adapted for use with a two - compartment case, by solving appropriate mass -balance equations. The mass -balance equation for each compartment , neglecting sinks (see **Section 3. 6**  ), is as follows : 

## 

      i Zone in sources num k k

i i ij i i j ji i i i E C Q C Q C Q C Q dt dC V 1 , 0 0 0 (Eqn. 3 - 9 ) where: V

i = volume of compartment i (m 3 ) C i = concentration in compartment i (mg/m3 ) t = time (hrs) i,j = indoor compartments ( 0 signifies the outdoors) Qi j = flow rate from compartment i into compartment j (m 3 /hr) Ei,k = emission rate for formaldehyde source k in zone i (mg/hr) It is acknowledged here that there are formaldehyde sources other than pressed-wood products in the indoor environment; however, such emitters (e.g., tobacco smoke, permanent press fabrics, paints, cosmetics) ty

pically are comparatively weak. Together, the outdoor concentration and these weaker emitters contribute to what can be described as a "background" concentration. As an expedi ence, for purposes of this model, the background concentration is treated as if all such contributions can be represented by the outdoor concentration. Studies of background concentrations indicate that the concentrations indoors are generally offset from outdoors due to these other sources by approximately 5 ppm (see **Section 2.**  **2.2** ). Although the emission rate of these other formaldehyde sources can be impacted by the presence of new sources such as PWPs , this impact is expected to minimal. Therefore, treating these other sources as an outdoor contribution provides a meaningful construct for isolating the impact of the new sources, by providing a constant background offset. With this representation, equation 3 - 9 can be alternately expressed as follows: 

## 

      i Zone in sources num k k

i i ij i i j ji B i i i E C Q C Q C Q C Q dt dC V 1 , 0 0 (Eqn. 3 - 10 ) where: C

B = background concentration, which is defined as the outdoor concentration plus the contribution from indoor sources other than pressed-wood products (assumed to be constant over time) . Considering the source equation as described in Equation 3 - 5 for multiple pressed-wood products in either zone, the sum of these emission sources in each compartment can be expressed as: 

#          k k k i k i i k i k i k k i k i k i Area b C Area m Area OER CH E , , , , , ' , 2 , * * * * (Eqn. 3 - 1 1 ) where: CH

2 OER  i, k = unit emission rate of source k located in compartment i

(mg/m2

-hr)40 Area i,k = area of source k located in compartment i (m2 ) m i,k = mass transfer coefficient of source k located in

compartment i (m/hr) b i,k = emission rate at zero CH2 O air concentration for source

k located in compartment i (mg/hr) C i = CH2 O air concentration in compartment i (mg/m2 ). Considering the combined E quations 3 - 10 and 3 - 1 1 for each compartment, and solving simultaneously

f or the steady- state condition (see **Appendix A** ) , the following equation s are obtained: 

##    

  2 1 21 1 20 1 2 12 20 12 2 10 21 10 20 10 2 21 1 2 21 20 02 21 2 01 21 01 20 01 , 1 z z Q z Q z z Q Q Q z Q Q Q Q Q y Q y z Q Q C Q Q z Q Q Q Q Q C B SS                (Eqn. 3 - 1 2 ) 

##       1 2 12 2 10 2 1 21 10 21 1 20 12 20 10 20 1 12 2 1 12 10 01 12 1 02 12 02 10 02 , 2 z z Q z Q z z Q Q Q z Q Q Q Q Q y Q y z Q Q C Q Q z Q Q Q Q Q C B SS                (Eqn. 3 - 1 3 ) where: SS = indicates the steady- state solution

z 1 = k

Zone in sources num k k Area m 

## 

 1 1 for the k sources located in compartment 1 y 1 = k

Zone in sources num k k Area b 

## 

 1 1 for the k sources located in compartment 1 .

z2 = k

Zone in sources num k k Area m 

## 

 2 1 for the k sources located in compartment 2 y2 = k

Zone in sources num k k Area b 

## 

 2 1 for the k sources located in compartment 2 . **3.4 Matthews Model Compared to HBF Model**  An alternative to the Matthews model is the HBF model (name coined by Myers 42 ), a model developed b y Hoetjer43 for which mathematically identical versions have been developed b y Berge et al. 44 and by

Fujii et al. 45 The underlying theory and derivation of the model have been summarized by

Myers. 42 G Myers. 1984. Effect of Ventilation Rate and Board Lo ading on Formaldehyde Concentration: A Critical Review of rhe Literature. Forest Products Journal 34: 59 - 68. 43 J Hoetjer. 1978. Introduction to a Theoretical Model for the Splitting of Formaldehyde from a Com posite Board. Methanol Chemie Netherland, June 8 . 44 A Berge, B Milligaard, P Haneto, and E Ormstad. 190. Formaldehyde release from Particl eboard

– Evaluation of a Mathematical Model. Holz als Roh - Und Werkstaff 38:251 - 255. 45 S Fujii, T Suzecki, and S Koyagaehiro. 1973. Study on Liberated Formaldehyde as Renewal for JIS Particleboard. Kenjal Shiken Joho 9: 10 - 14.41

The HBF model formulation for the steady- state concentration for a single source is as follows: C SS = C EQ / (1 + N / kL ) (Eqn. 3 - 1 4 ) where: C

SS = the steady- state formaldehyde concentration (mg/m 3 ) C EQ = the formaldehyde equilibrium concentration (mg/m3 ) N = the air exchange rate (1/hr) k = mass transfer coefficient (analogous to m in Matthews model) (m/hr) L = product loading ratio (m2/m 3 ) Itc an be shown that t

he Matthews and HBF formulations are identical models and that C EQ = b/ m . The only difference between the two models is in the regression equations that are used to derive the parameters, not their theoretical constructs. The Matthews formulation, under the assumption that the outdoor concentration is zero, can be expressed as follows b y substituting Equation 3 - 5 into Equation 3 - 4: C SS = ( - m * C

SS + b ) * Area / Q (Eqn. 3 - 1 5 ) where C

SS is as defined above and m , b , Area and Q are as defined previously in **Section 3.2.** Substituting ACH * VOL for Q , Equation 3 - 1 5 can be expressed as: C SS = ( - m * C

SS + b ) * Area / (ACH * VOL) (Eqn . 3 - 1 6 ) Equation 3 - 1 6 can be expressed using the same terms as in Equation 3 - 1 4 , by setting N = ACH and by setting L = (

Area / VOL ): C SS = ( - m * C

SS + b ) / (N /L) (Eqn. 3 - 1 7 ) Equation 3 - 1 7 can be solved for C SS as follows: 

###  (Eqn. 3 - 1 8 ) Setting the Matthews (Equation 3 - 1 8 ) and HBF (Equation 3 - 1 4 ) formulations equal to each other yi elds the following equality : (Eqn. 3 - 1 9 ) Equation 3 - 1 9 can be solved for C EQ as follows: (Eqn. 3 - 20 ) Therefore, setting C EQ = b/ m leads to identical model formulations.42

**3.5 Other Potentially Useful Modeling Constructs**  One of the peer reviewers commented on the potential utility o f the saturation concentration (C sat) of formaldehyde in air over an emitter of interest, as follows: Equation 3 - 5 is reproduced below with slightly different notation along with an equivalent equation from my previous work:

max ) ( G C m G ss ss    (Equation 3 - 5 with different notation) G ss = steady state emission rate (mg/m 2

- hr). Equivalent to CH 2 OER’ Gmax = the maximum emission rate which occurs at zero backpressure; that is, at zero concentration of formaldehyde in the air (mg/m 2

- hr). Equivalent to b. m = the mass transfer coefficient (m/hr) C ss = vapor-

phase concentration of formaldehyde at stead y state (mg/m 3

). Equivalent to [Ch 2 O] v Equation 3 - 5 above is essentially identical to an algorithm that I have often used for backpressure modeling , shown below: C sat = the saturation concentration (mg/m 3 ) of formaldehyde in the air over the emitter of interest. That is the concentration that would be expected in a volume (with high surface area/volume ratio) in which the emitting walls were made up entirely of the emitter of interest and there is zero ventilation. Note the equivalence of this last equation to Equation 3 - 5 above and the identity of m:

sat 

### C G m max 

###  Clearly, the relatively straightforward analytical measurement of C sat could provide a potentially valuable extended methodology for the evaluation and development of the model’s parameters relative to specific emitters. Several peer reviewers suggested possible alternatives to the exponential - decay model used in FIAM - pwp to represent declining formaldehyde emissions over time. One suggestion was that a power- law model may

b e more suitable and another suggestion was the use of an expression with multiple or changing decay rates to represent , for example, “fast” (earlier) and “slow” (later) periods of exponentially

declining emissions. Brown46 fitted a double - exponential model to results from chamber experiments, noting that “the high but decreasing emission rates in the first 3 months were consistent with free formaldehyde and formaldehyde produced from easily hydrolys ed chemical bonds ” and that “longer-term, near- constant emissions may b e due to ongoing hydrolys is of resins used in the wood panels .” One peer reviewer noted a conceptual model47 with three exponential - decay

compartments , attributed to three potential sources of formaldehyde emissions:  Free formaldehyde (short-term compartment);  Decay of paraformaldehyde and other complex structures (medium-term compartment); and  Hydrolysis of the resin (long-term compartment). 46 Brown, S.K. 1999 . Chamber A ssessment of F ormaldehyde and VOC Emissions from Wood-B ased P anels . Indoor Air 9: 209

–215. 47 L. Mølhave, L. Dueholm, and L.K. Jenson. 1995 . Assessment o f Exposures and Health Risks Related to Formaldehyde Emissions f rom Furniture: A Case Study . Indoor Air 5: 104 - 119. max max max ) ( : ) 1 ( G C C G G rearranged C

C G G

ss

sat ss sat

ss ss

    43

A single - exponential model for declining formaldehyde emissions over time has the following form: **ER(t) = E**

**R( 0**  **) e**  **- kt**  Where: **ER(t)** is the emission rate at time t (e.g., elapsed hours) ; **ER(0)** is the initial emission rate (t = 0); and **k** is the rate constant governing the exponential decline in the emission rate. The power- law function takes the following form: **ER (t)**  **= at -** **k** Where **a** is a constant and **k** is an exponential index, dimensionless. Although the power- law function is undefined when **t** is zero, an initial emission rate can be “ set” by assigning an arbitrarily

small value to **t** (the rate is highly sensitive to the value chosen for **t** ). The plots in **Figure 3**  **- 1**  illustrate the declining behavior of the power- law function , with a set to 50 and **k** set to 0.25, in comparison to the single - exponential model , with **ER(0)** set to 90 and **k** set to either 0.1 or 0.5. The power- law function generally has a sharper curvature than the exponential model. This sharper curvature can be matched to an extent with the exponential model, but only by choosing a more rapidly declining emission rate (e.g., with **k** set to 0.5 as in the f igure) . The shape of the time - related decline obtained using the power- law function can be nearly matched by the exponential - decay

model , however, when it is modified to hav e an initial period of faster decline followed by

as econd period of slower decline 48 , as illustrated in **Figure 3**  **- 2**  . If, for example, the conceptual model above with three potential sources of formaldehyde emission is a representative construct, then the approach of using multiple exponentials as a semi - empirical approximation may b e pref erable (recognizing the associated need for estimating multiple parameters) because first- order processes are exponential in form . An example application of FIAM - pwp with a varying decay rate is provided in **Section 2.7.5** . The above constructs, although potentially useful, currently share one limitation

– little existing data to provide a basis for assigning appropriate parameter values. They s hould be kept in mind, however, for future research efforts and modeling applications. By c omparison, as described in **Section 3.8**  , there has been a fair amount of research on the formaldehyde emissions half life, providing some basis for choosing a value for the rate of decline for the simpler single - exponential decay model.

48 The use of changing values for the exponential decay can be viewed as a sim plified or constrained version of the double - exponential mo del; the full, or unconstrained, model wo uld use both exponentials in parallel rather than in series. The current configuration of FIAM - pwp does not allow

use of the full double - exponential mo del, due in part to uncertainty regarding appropriate parameter values to assign to the rate constants for faster and slower decline. Faster and slower exponentials can be applied sequentially, as done here, with FIAM - pwp by making a series of two related model runs, as illustrated in **Section 2.7.5** .44 **Figure 3**  **- 1**  **. Representation of Declining**  **Emission Rate by**  **Power -** **law Function vs.**  **E xponential** **- decay**  **Model.**

**Figure 3**  **- 2**  **. Representation of Declining Emission Rate by Power** **- law Function**  **vs. Exponential -**  **decay Model with Periods of Fast and Slow Decay.**45

**3. 6**  **Discussion of Indoor Sinks**  In concept, the treatment of indoor sinks in the calculation module could be accomplished within the model framework by recognizing that the emission term, as given by E quation 3 - 5, is comprised of two components. The first component ( - m*[CH

2 O] v) is in the same form as a firstorder sink representation. The second component (b ) is a constant, representing a constant emission rate. By

s etting b equal to zero and m to a nonzero value, this “ source ” representation actually reflects the behavior of a first- order sink. Alternatively, setting m to zero and b to a nonzero value represents a product as a constant emitter. Recognizing these behaviors, the source term c ould be used to represent a simplistic sink by assigning a large enough value to m to result in a net flux of formaldehyde into a material that acts as a sink. H owever, this simplistic approach does not allow a fully realistic representation of the re - emission from sinks that has been observed in laboratory and field studie s. Inthe model, the concentration in a compartment is assumed to decline from an initial “ steady- state ” concentration in accordance with a user- specified half - life. This model representation tends to diminish the effect of the sink over time, much like the emission rates for materials that act as sources. In reality, sinks for formaldehyde tend to accumulate mass when air concentrations are high, and to re - emit this mass as the air concentration decreases. The accumulation rate in the sink at any point in time is a function of the air concentration and the mass residing in the sink at that point, as well as other sink characteristics. Because the complex relationships such as those described above cannot be fully c aptured by using the current modeling framework to represent sinks, it is recommended that users do not attempt to model sinks using FIAM - pwp . Ignoring the potential effects of indoor sinks will tend to result in a more conservative estimate, that is, higher modeled concentrations. The magnitude of prediction error with exclusion of indoor sinks is believed to be relatively small, on the order of 10 % for most formaldehyde modeling situations. **3. 7**  **Decay of Indoor Concentrations** The initial (steady- state) indoor formaldehyde concentration, as calculated by the model described above, is assumed to decrease over time as the reservoir of formaldehyde in various sources and sinks is gradually

depleted. The decrease in the initial value over time is assumed to f ollow a firstorder exponential process, expressed as follows:



##   -kt

B i B t e

C C C C



  (Eqn. 3 - 2 1 ) where: C

t = formaldehyde concentration indoors (ppb ) at time t (in years) , due to the combination of background concentration and emissions from PWPs (Note: C

t = C i at t = 0) C B = background concentration (ppb ), which is defined as the outdoor concentration plus the contribution from indoor sources other than pressed-wood products (assumed constant) C i = initial concentration indoors (ppb ) k = first- order rate constant for the exponential decline (years - 1 ).46

Note that , in Equation 3 - 21, only the contribution from the new PWPs (i.e., C i - C B) is decayed because the background contribution is assumed to be constant , as discussed in **Section 3.3**  . The value of k is determined from the user- specified half life for the indoor formaldehyde concentration, assumed to be dominated by an exponential decay

in formaldehyde source strength. Solving for t results in the following equation:

k C C C C t B

t B i      

 

 ln (Eqn. 3 - 2 2 ) S olving for k results in the following equation:

t C C C C k B

t B i      

 

 ln (Eqn. 3 - 2 3 ) Neglecting for the moment the background contribution to the indoor concentration (i.e., assuming that the background concentration is zero), E quation 3 - 2 3 reduces to:

t C C k t

i      

 ln (Eqn. 3 - 2 4 ) By definition, C

t is equal to half of C i when the half

- life is reached: 5 . 0  i T C C (Eqn. 3 - 2 5 ) where: T = half

- life (in ye ars). By substitution, Equation 3 - 2 4 becomes: 

##   T k 2 ln  (Eqn. 3 - 2 6 ) S ubstituting the default half life of 1.5 ye ars (see **Section 2.2**  ) for T in the above equation gives: k = 0. 462 ye ars - 1 Indoor concentrations at later points in time (i.e., subsequent to the initial, steady- state values for each zone) are calculated by decaying only

the portion of the indoor concentration that is attributable to indoor pressed-wood products. For example, to obtain the indoor concentration 3 months (0.25 years) after the initial value, with an assumed half - life of 1.5 years, E quation 3 - 2 1 woul d apply : C(0.25 yr) = C

B + (C i - C B ) e- 0. 462 *0.25 (Eqn. 3 - 2 7 )47

If C i were 50 ppb and the background concentration were zero, then the indoor concentration three months later would be 44.5 ppb . With the default background concentration of 7.5 ppb (see **Secti on**  **2.2** ) , the indoor concentration would be 57.5 ppb initially and 52 ppb after three months. In either case, the portion of the initial indoor concentration due to indoor pressed-wood products (50 ppb) would be reduced by 5.5 ppb over three months with a half life of 1.5 years. The time required for the initial indoor concentration to decay to a user- specified concentration (e.g., 10 ppb, the default value) can be determined from the first- order exponential process using E quation 3 - 2 2 as follows , given an initial indoor concentration greater than the specified concentration and assuming a background concentration of zero: t = ln ( C

i / 10) / k (Eqn. 3 - 2 8 ) Continuing with the above example , where k is 0. 462 ye ars - 1 and C i is 50 ppb , by

substitution into E quation 3 - 2 8 we get: t = ln (50 / 10) / 0.462 (Eqn. 3 - 2 9 ) for which the value of t is 3.48 ye ars, or 41.8 months. The model uses the higher of the two initial indoor concentrations, when a two - zone model is selected, for the calculation. Because the user is allowed to specify a b ackground concentration other than zero, which is assumed to be constant over time, E quation 3 - 2 2 can be used to account for the background contribution while decaying only the component due to indoor sources and sinks: k C

C C t B

B i      

 

 10 ln (Eqn. 3 - 30 ) With the default background concentration of 7.5 ppb and an initial concentration of 57.5 ppb, the value for t would be 6.48 ye ars. The result from E quation 3 - 30 is multiplied by 1 2 and reported in months. If the highest initial indoor concentration is lower than the background concentration , then zero months is reported as the time required for the indoor concentration to decay to background.48

**3. 8**  **Default Value for Half Life** Ideally, an appropriate half - life value for representing the long-term decay o f formaldehyde emissions and concentrations in residences would be determined by taking measurements in a house soon after it was loaded with pressed-wood products and at periodic points in time over the next several years. Continuing with this ideal situation, the products would not change throughout the measurement period and factors such as indoor temperature and humidity, as well as the indoor- outdoor air exchange rate, would change only minimally

in response to outdoor weather conditions and occupant activities indoors. Further, the experiment would be repeated in several houses. The data for each house would be analy zed to fit a nonlinear (e.g., exponential) decay function to the time -varying indoor concentrations, and the resultant estimates would be compared across houses (or the data would be pooled across houses) to determine an appropriate central value for the concentration half life. The ideal data set has not been collected, however, most likely b ecause the complexities and costs of multiple measurements over time, coupled with the need to restrict certain occupant activities over several ye ars (or to operate a research house to gain experimental control), would be prohibitive. There are two practical alternatives to the ide al experimental situation, both of which have been attempted: (1) collect or assemble point- in-time measurements from houses of varying ages, as a proxy for the time -related decay in one or a series of houses; and (2) conduct chamber tests at periodic points in time for pressed-wood products, either individually or in combination. Either alternative has significant limitations. For example, cross - sectional data from many houses are, at best, a crude proxy f or the time -related behavior of a single house, or of a limited set of well - characterized houses

– the analys is is confounded by varying, and generally unknown, construction features, occupant activities and weather conditions at the times of measurement. Chamber tests, on the other hand, have the advantage of careful experimental control. However, for multiple tests over time, the material to be tested ty pically would not be kept in the chambercontrolled environment throughout the testing period, but rather during only the relatively brief occasions when measurements were to be taken. Further, most such tests have been conducted only for a single product or material. The time -related rate of decline depends on the formaldehyde concentration ; the rate of decline is more rapid for a single product because other products are not present to increase the formaldehyde concentration and thereby retard its rate of formaldehyde release. Limited tests of product/material ensembles have been conducted, but none have included the full array

of sources and sinks that typi cally would be present in an occupied house. With these limitations in mind, some previous investigations into the half life of formaldehyde emissions or concentrations are summarized below. As summarized in a Versar 1988 report49 , estimates of decay half lives for formaldehyde concentrations in residences range from 2 to 44 years, with most estimates below 5 ye ars. These estimates have been based largely on pooled cross - sectional data across a variety of residences, as a proxy for time - series data from one or a few houses. Iti s noteworthy that the higher estimates (20 to 44 ye ars) are from data sets involving houses aged from new to 50 years, whereas the lower estimates (2 to 4 ye ars) are from data sets where the houses generally were 10 years old at mo st. If none of the materials or furnishings in a house were to be changed, and if the occupants were to 49 Versar. 1988. Formaldehyde Expos ure in Residential Settings: Sources, Levels, and Effectiveness of Control Options. Update (September 30, 1988) of 1986 report by Versar, Inc. for the USEPA Office of Toxic Substances, prepared under Contact No. 68 - 02 - 3968.49

avoid using consumer products that emit formaldehyde, then the indoor concentration could be expected to eventually decay to some background level, simi lar to that if no sources were present. As a house ages, however, occupants will tend to add or replace materials and furnishings, some of which may

emit formaldehyde. Such changes, then, will introduce new sources, thereby raising the formaldehyde concentration relative to the no - change case and artificially inflating the half

- life estimate. The above conjecture is partly supported by

l imited studies involving repeat measurements at different points in time from one or two houses, for which the half - life estimate ranged from 2.0 to 2.6 years. A careful analysis by Versar of a cross - sectional data set for 396 manufactured homes, as described in the 1988 report referenced on the previous page, resulted in a half - life estimate of 2.92 ye ars. This estimate is believed to be an upper bound for the true half life in a house that has some significant formaldehyde sources from the outset of its construction and occupancy history . Chamber studies to investigate the decay o f formaldehyde have focused primarily on individual sources and, not surprisingly, have produced shorter half - life estimates than most residential studies. As summarized in the same (1988) Versar report, the estimated half lives from chamber studies have ranged from 0.2 to 2.58 ye ars. One noteworthy investigation, conducted by Matthews et al. 50 , involved a combination of sources (particleboard, hardwood ply wood paneling and MDF) under controlled environmental conditions (23  C and 50 % relative humidity). The “slow” decay study, with an air exchange rate of 0.4 air changes per hour (ACH) in the chamber, produced a half - life estimate of 1.52 years. The “fast” decay study was conducted with relatively high air exchange rates designed to keep the chamber formaldehyde concentration below 0.1 ppm. The lower background concentration was expected to increase the emission rates and, thus, shorten the decay periods relative to the “slow” decay study . Resultant half

- life estimates were 0.76, 0.62 and 1.08 years for particleboard, paneling and MDF, respectively . Of the two decay

studies by

M atthews et al., the “slow” study i s believed to be more indicative of the formaldehyde decay

b ehavior in residences. However, the authors added the caution that care should be taken in interpreting the study results. For ex ample, the duration of the study may have been inadequate to accurately reflect the emission decay p eriod for the collection of sources. In addition, the data may

reflect a relatively rapid decay o f emissions from a few of the strongest emitting sources, as opposed to the entire collection of products, whereas in real life one might ty pically expect to find a combination of relatively strong and weak emitters, or of sources and sinks. In another decay

study f or an individual source, Zinn et al. 51 estimated an apparent half - life of 216 days (0.6 ye ars) 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

50 T. Matthews , T. Reed, B. Tromb erg., K. Fung, C. Thom pson, J. Simpson, and A. Hawthorne . 1985. Modeling and Testing of F

ormaldehyde Emission Characteristics of Pressed - Wood Products: Report XVIII to the U.S. Consumer Product Safety Commission . ORNL/TM - 9867, Oak Ridge National Laboratory , Oak Ridge, TN. 51 Zinn, T.W., Cline, D. and Lehmann, W.F. 1990 . Long - term Study of Formaldehyde Emission Decay from Particleboard. Forest Products Journal 40(6): 15 - 18.50

decay model. The Zinn et al. logarithmic equation was used by CARB 52 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 f or 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 yi eld 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 ye ars 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 - ye ar 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 53 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 c ontain 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 ye ars 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 ye ars and the other (Groah and Gramp 54) indicated a half - life of 2.10 ye ars. Based on these studies, a halflife on the order of 1.5 to 2.0 ye ars is suggested should the user wish to apply a less conservative value.

52 California Air Resources Board (CARB). 2007. Initial Statement of Reasons for Propos ed Rulemaking, Proposed Airborne Toxic Control Measure to Reduce Formaldehyde Emissions from Composite Wood Products . Available at: http://www.arb.ca.gov/regact/2007/compwood07/fro - f inal.pdf .. 53 W. Groah. 2005. Decay or the Decrease in Formaldehyde Concentrations or Emissions over Time and UFbonded Wood Panel Products . Report prepared for the Composite Panel Association, Formaldehyde Council Inc., Hardwood Plywood and Veneer Association, and the Kitchen Cabinet Manufacturers Association. 54 W. Groah and G. Gramp. 1988. An Estimate of Home Occupant Exposures to Formaldehyde Gas from Plywood and Reconstituted Wood Products Bonded with Formaldehyde Based Adhesives . CPA/HPVA 1988 Exposure and Assessment Package Report, Hardwood Plywood and Veneer Association, Reston, VA. Available at: http://www.ecobind.com/research/Decay_or_Decrease_in_Emissions.pdf .51

**3. 9**  **Temperature and Humidity Adjustments** As noted in **Section 2**  and in the introduction to this section, the model initially e stimates 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 55 , 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:

   

U B T T R T 

### e C C 1

1 0  

###  (Eqn. 3 - 3 1 ) where: CT = Temperature - adjusted formaldehyde concentration C0 = Formaldehyde concentration at the baseline temperature R = Temperature coefficient for adjustment T U = User- specified temperature,  K T B = Baseline temperature, 296  K (23  C). The humidity

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

##  

U B T TH H

H A C C

   1 (Eqn. 3 - 3 2 ) where: CTH = Temperature - and humidity- adjusted formaldehyde concentration CT = Temperature - adjusted formaldehyde concentration A = Humidity

coefficient for adjustment H U = User- specified relative humidity, % H B = Baseline relative humidity, 50 %. Combining equations 3 - 3 1 and 3 - 3 2 , the temperature - and humidity- adjusted concentration can be expressed as follows: TH TH K C C 0  (Eqn. 3 - 3 3 ) where K

TH is the combined temperature and humidity adjustment factor:     

##  

U B T T R TH H

H A e K U B

    1 1

1 (Eqn. 3 - 3 4 )

55 ASTM . 1996a. Standard Test Method for Determining Formaldehyde Concentrations in Air and Emission Rates from Wood Products Using a Large Chamber . Designation E 1333 - 96 (Reapproved 20 10 ), American Society for Testing and Materials, Philadelphia, PA.52

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. 56 for two Norwegian particleboard specimens. These coefficients were used by HUD in setting the 1984 standards for particleboard and hardwood ply wood paneling, and also have been used in ASTM, ANSIand Composite Panel Association ( CPA) standards or guidelines. Chamber tests underlying these coeffici ents were conducted at two temperatures (22 and 28  C) and at two relative humidities (30 and 60 %). The coefficients reported by B erge et al. were 9799 for temperature (assumes an Arrhenius ty pe of model) and 0.0175 for humidity ( assumes a linear model). The second set of coefficients was reported by Myers 57 , who reviewed the extant literature and developed his recommended temperature coefficient based on chamber testing of about 40 specimens (particleboard and hardwood ply wood paneling) from 11 laboratori es. The temperature range of the product tests was from 20 to 40  C. Dr. Myers also developed a humidity c oefficient, but expressed little confidence in the number; the relative humidities in the tests on which the correction factor was based ranged from 2 0 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 concentrati on 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 c oncentrations calculated using E quations 3 - 1 2 and 3 - 1 3 takes the following form:



#   B TH B SS adjusted SS 

### C K C C C 

  *

, 1 , , 1 (Eqn. 3 - 3 5 ) 

#   B TH B SS adjusted SS 

### C K C C C 

  *

, 2 , , 2 (Eqn. 3 - 3 6 ) Similarly, the adjustment applied to the one - zone concentration calculated using E quation 3 - 8 takes the following form: 

##    



##   B TH B SS adjusted SS 

### C K C O CH O CH    *

2 , 2 (Eqn. 3 - 3 7 )

56 A. Berge , B. Mellagaard, P. Hanetho, and E. Ormstad. 1980. Formaldehyde Release from Particleboard

– Evaluation of a Mathematical Model. Holz Als Roh - und Werkstoff 38: 252 - 255. 57 G. Myers. 1985. The Effects of Tem perature and Humidity on F ormaldehyde Emission from UF - bonded Boards: A Literature Critique. Forest Products Journal 1985: 35:20 - 31.53

**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 ye arly increments, by integrating Equation 3 - 2 1 . The value of this integral , between two times ( t1 and t 2) that are exactly one ye ar apart, is as follows: ADC = (( C

i - C B )/ -k ) *e-k*t2 + C

B *t 2 - (( C i - C B)/-k ) *e-k*t1

- C

B *t1 (Eqn. 3 - 3 8 ) where:C

i = initial concentration indoors (ppb ) C B = background concentration indoors (ppb ) k = first- order rate constant for the exponential decline (years - 1 ) t1 = starting time (years) t 2 = ending time (years). F or a new house, the values of t1 and t 2 for the first year are 0 ye ars and 1 year, respectively. The t1 and t 2 values are 1 and 2 ye ars for the second ye ar, 2 and 3 ye ars for the third ye ar, and so on. If, for example, the starting concentration (i.e., at t1 = 0 ye ars) were 57.5 ppb, the background concentration were 7.5 ppb, and the value of k were 0. 462 ye ars - 1 (half life of 1.5 years), then the ending concentration would be 39 ppb per Equation 3 - 2 1 and the value of the integral for the first ye ar would be 47.5 ppb per Equation 3 - 3 8 . The percent of time during which the concentration in a modeled zone is greater than the LOI also is calculated in ye arly increments, as follows: % Time = 100 * (

ln (C i- C B ) - ln (LOI

- C B )) / k

– t

2 ) (Eqn. 3 - 3 9 ) where: % Time = percent of time concentration is greater than LOI LOI = level of interest (ppb ) . Continuing with the example where C i = 57.5 ppb, C

B = 7.5 ppb, and t1 = 0 (i.e., new house), and with a value of 10 ppb for the LO I, the c alculation result for each of the first six ye ars (i.e., for t 2 ranging from 1 to 6) is equal to 100%. For year 7 ( t 2 = 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 ye arly 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 = ( H Z1 *ADC

Z1 + H Z2 *ADC

Z2 + H

WSD *C W

SD + H

V *C V+ H

O *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 254 C = concentration at location away from home (ppb) WS D 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 - 3 8 , whereas concentrations in locations outside or away f rom the home or modele d structure are assumed to be constant across the ye ars. The sum of hours across the various locations (Z1 , Z2 , WS D , 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.55



### 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 conc entration 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 o f minor errors in an earlier version in the handling of ppm vs. mg/m3 units for the background concentration (now ppb and μg/m 3 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 res earchers 58 at the National Institute of Standards and Technology (NI ST) to validate the Matthews model on which this model is based . P arti cleboard underlay ment, hardwood-plywood paneling and medium- density f iberboard (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 diff erent combinations , and e quilibrium 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" ofpressed - wood products. Formaldehyde emission results from the difference in concentration between this "bulk phase" and the atmosphere, in accordance with Fick's first 58 S. Silberstein, R. Grot, K. Ishiguro, and J. Mulligan. 1988. Validation of Models for Predicting Formaldehyde Concentrations in Residences due to Pressed-Wood Products. JAPCA 38: 1403 - 1411.56

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 ply woo d or hardwood ply

wood paneling. Thus, the NI ST 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 asse ssment 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 pres s ed-wood products. The asses sment 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 ty pe 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 ty pe 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 conc entration 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 c onditions (23  C, 50 %) and a usersupplied 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 c oefficients 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 major57

sources installed in the conventional house – underlay ment, 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 p ertain to each modeled case. There are two major ty

pes 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 l evels were not measured downstairs; as noted previously, upstairs values for temperature and humidity w ere 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 m 3 ) and an assumed loading ratio of 0.43 m2/m 3 , or 131 m2

. For wallboard the loading ratios for walls (0.95 m2/m3 ) and ce ilings (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 ply wood. An intercept value of 0.04 mg/m2

-h was chosen for wallboard after running the mode l with ply wood 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/m 2**  **- h)**  **Area (m 2** **)** Softwood ply

wood - 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 ply wood as the only

source, and without including wallboard as a sink, the modeled values for the conditions under which measurements w ere 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. Iti s 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.58 **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 ply

wood 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 site s (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**  ). Ply wood was not included as a source because it was covered by underl ay ment or by

f loor 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, ind ustrial 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 Si** **nks ) for First (Medium) Loading**  **Source/Sink Slope (m/h)**  **Intercept (mg/m 2**  **- h)**  **Area (m 2** **)** Underlay ment - 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 **Appe ndix**  **A**) . The addition of carpeting lowered the modeled concentrations slightly, and further addition of wallboard lowered the modeled values by a bout 10 percent compared to estimates with no sinks. The modeled concentrations for measured conditions, with c arpeting and wallboard included, were 5 - 10 ppb higher than measured values under those conditions.59 **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 Underlay ment, 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, ply wood 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/m 2**  **- h)**  **Area (m 2** **)** Softwood ply

wood - 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 p ossibility

that the wallboard had released a fair amount of mass during the air- out period, are closer to the measurement results.60 **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 ply

wood 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 wal lboard 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 underlay ment and with the addition of hardwood ply wood 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. **T able**  **4 -**  **7. Model Inputs (Sources and Sinks) for Second (High) Loading**  **Source/Sink Slope (m/h)**  **Intercept (mg/m 2**  **- h)**  **Area (m 2** **)** Underlay ment - 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 1 2), 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 d ue 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.61 **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 Underlay ment, 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**  **A ir**  **- out Period after Second Loading**  For the air- out period after the second loading, the only sources and sinks again were ply wood 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/m 2**  **- h)**  **Area (m 2** **)** Softwood ply

wood - 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.62 **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 ply

wood 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/m** **2 -**  **h) Area (m** **2 )**  Underlay ment - 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.63 **Table 4**  **- 12. Modelin**  **g 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 Underlay ment, 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 ty pically agreed with measurement results within ± 25 percent. **4 .**  **4 FIAM** 

**- pwp**  **Predictions for R** **ecent Residential**  **Field Monitoring Studies 59**  Recent (i.e., since ye ar 2000) residential formaldehyde field studies of note are summarized in **Table 4**  **- 13**  . The first two studies

– Offerman et al. (2 008) and Hodgson et al. (2000)

– both were conducted on new homes, with the Offerman study c overing 100+ new single - family homes in California and the Hodgson study c overing 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 b y 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 Lo s 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 2 007 - 2008 the CDC measured formaldehyde levels in 500+ structures of the ty pes (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

(LB NL ; Maddalena et al. 2008) studied four FEMA temporary

housing units (camper trailers) to assess indoor emissions of aldehydes and other VOCs. Measured formaldehyde level s in these structures ranged from 269 to 753 ppb. 59 References cited here are listed below **Table 4 -**  **13** ; portions of this section have been extracted from the following source : USEPA . 2012. Formaldehyde from Composite Wood Products: Exposure Assessment. Draft Final Report. U.S. Environmental Protection Agency, Office of P ollution Prevention and Toxics, Exposure Assessment Branch, 1200 Pennsylvania Avenue NW, Washington, DC 20460. July 2012.64 **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 (5 th

- 95 th 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 indooroutdoor 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: 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. Com parison 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 Californi a 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 Com

pounds in Inner - City Residences of New York City and Los Angeles. Journal of Exposure Analysis and Environmental Epidemiology 14 (Supplement 1): S95 - S109.65

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 o f new California homes and the CDC (2008/2010) study o f recently constructed travel trailers. In both cases, the predictions were made relying primarily on model defaults, occas ionally supplemented in cases where ancillary study m easurements 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 cond ucted 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 H ouse S creen. 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 yi eld an air exchange rate of 0.33 ACH.

**Figure 4 -**  **1. FIAM** 

**- pwp**  **House -**  **Screen Inputs Used**  **to Model St udy 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.66

**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/m 3 ) for these homes following construction. By c omparison, the authors of the paper reported a median concentration of 31.1 ppb ( 38.3 μg/m 3 ; 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/m 3 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/m 3

.

**Figure 4 -** **3 .**  **FIAM**

**- pwp**  **Results for Model** **ing of New California Homes.** 67

Travel trailers accounted for nearly 70 % of the structures that were monitored by CDC (200 8/2010). The structure ty

pe 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

C DC. However, from the information given in the CDC report , the trailers were approximately

one to two ye ars 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 b e 66.2 ppb.

**Figure 4 -**  **5 .**  **FIAM**

**- pwp**  **Results for Model** **ing 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**  60

60 Portions of this appendix have been extracted or adapted from the following sources: D. Hare, R. Margosian, W. Groah, S. Abel, G. Schweer, and M. Koontz. 1996. Evaluating the Contribution of UF bonded Building Materials to Indoor Formaldehyde Levels in a Newly Constructed House. In Proceedings of the 30th International Particleboard/Composite Materials Symposium , Washington State University, Pullman, WA , pp. 93 - 108. Available at: http://www.ecobind.com/research/Evaluating_the_Contribution.pdf . M. Koontz, H. Rector, D. Cade, C. Wilkes, and L. Niang. 1996. Residential Indoor Air Formaldehyde Testing Program: Pilot Study . Report No. IE - 2814, prepared by GEOMET Technologies, Inc. for the USEPA Office of Pollution Prevention and Toxics under EPA Contract No. 68 -D3 - 0013.A- 1

**A.1 STUDY OBJECTIVES AND DESIGN**  At a public meeting in January 1 993, EPA representatives outlined a plan for a proposed formaldehyde (HCHO) s tudy 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 locate d 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 p ilot study in newly constructed conventional and manufactured houses. The general purpose of the p ilot 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 p ilot 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 s ystem. The study w as guided by

a Quality A ssurance 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 p ilot study would include one unoccupied, conventionally built , single - family house and four unoccupied manufactured houses. Four manufactured houses were specified in the p ilot study b ecause 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 sl ab or crawlspace. The manufactured-house portion of the pilot study eventually was dropped due to resource limitations.A- 2

The QAPP also specified that the following variables would be evaluated in the p ilot study :  Product emission characteristics : Only “medium” emitting products were to be used. Emissions from particleboard and from plywoo d 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 pro ducts

– 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 deter

mined 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 (SF 6 , EPA Method IP - 4B ). All USEPA methods cited on this page have been compiled in a compendium61

. 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 3 0 - day p eriod. At the completion of 30 - day p eriod, 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 b y 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 for maldehyde 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 s ystematically . 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:

61 USEP A. 1990. Compendium of Methods for the Determination of Air Pollutants in Indoor Air . Report No. EPA/600/4 - 90/010, Atmospheric Research and Assessment Laboratory, USEPA, Research Triangle Park, NC.A- 3

 Doors

– five do ors , 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 gy psum 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 styl e with a full basement (volume of 168 m 3 ) . 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 m 3 ). The first floor of the house ( 712 ft2 floor area) had 5931 ft3 (168 m 3 ) 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 m 3 ) of living space that consisted of two be drooms 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 pre ssed- wood products that would be used in the p ilot study . Sufficient quantities of 5/8” particleboard underlay ment, 3/4” industrial particleboard for countertops, 1/4” hardwood ply wood wall paneling (3 -ply b irch face, tropical hardwood back and core with 7 cut grooves along the length of each panel to simulate randomwidth 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 deter mined by A STM E 1333 at 0.5 ACH . All products were stored in a controlled- access warehouse until they w ere 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 parti cleboard underlay ment was installed with screws for easy removal. The kitchen and bath cabinets were screwed tightly against the wall. The ply

wood wall paneling was nailed to the wall to minimize damage to the gy psum wallboard.A- 4

**Table A -**  **1. Initial Emission**  **Characteristics of Products Used in the Pilot Study Product**  **Emissions, ppm Loading Rate, ft** **2 /ft** **3** Particleboard Underlay

ment 0.144 0.130 Ply wood 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 underlay ment 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 scenari o, particleboard underlayment was installed on both the first and second floors. In addition, twelve 4’ X 8’ sheets of ply wood wall paneling were installed. T o establish a relatively uni form 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 o f kitchen and bathroom cabinets and countertops (same number as for Medium loading) al so were installed. The total exposed surface area for cabinets was calculated to be 631 ft2 (59 m2 ). Particleboard underlay

ment was not installed in the kitchen and bathroom are as of the house , as those areas were covered by vinyl sheet goods that had been permanently installed during final preparation o f the house before field testing was initiated. **Table A** **- 2. Loading Areas for Pressed** **- wood Products at the Conventional House**  **Component Loading Area** **, ft** **2 1st Floor**  **2nd Floor Medium**  **Loading High** 

**Loading Medium** 

**Loading High** 

**Loading** Underlay ment 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 (s ervice penetrations between the basement and first floor and along the base plate) and seale d with caulk and foam. Numerous leaks also were found in the forced- air HAC distribution system. Sealing procedures reduced the leakage rate b y 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

p lans 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,A- 5

PFT sources and samplers were configured so that the average airflow rate between the basement and living area could be quanti fied during each sampling event. Following initial b aseline 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 l evels in the house , which reached over 70 percent. Humidity l evels were lowered to the desired range by adding additional dehumidification equipment in the house . Because high humidity c auses higher formaldehyde emissions, the house was declared to be in an “upset condition” during this time and it was decided that Lo ading- 1 products should be left in the house until conditions stabilized. The final reading s 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 p lan, which was modified for c onduct of only three loadings in the house

– one Medium and two High loadings . In addition, the air- out period between successive loading s was fixed at seven days instead of waiting for formaldehyde levels to reach equilibrium . Following the removal of Lo ading- 1 products f rom 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 Lo ading- 2 products f rom the house and a seven- day airingout period, Lo ading - 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

s ink-test results and results from Loadings 1, 2 and 3, it appeared that the gy psum 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 gy psum wallboard. Italso 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 underlay ment. The original protocol for “barrier testing” was modified to evaluate the floor system with both particleboard underlay

ment and carpet/padding, instead of just the carpet/padding. A sample of particleboard underlay

ment 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 (Inters can) analyz er. As a separate test, a second sample of particleboard with carpet/padding directly a bove 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 62

– the two pieces with the closest emission rates were used for the tests .

62 ASTM. 1996. Standard Test Method for Determining Forma ldehyde Concentrations in Air from Wood Products Using a Small-Scale Chamber . Designation D 6007 - 02 (Reapproved 2008), American Society for Testing and Materials, Philadelphia, PA.A- 6

**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 level s 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 (L oading 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 SF 6 . One possible reason for the discrepancy

i s the inherent difference between the two measurement technologies. The SF 6 method involves periodic injection and mixing o f the tracer through the HAC system, followed by real -time analys is as the concentration decline s . 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 Run**  **a Formaldehyde Concentration, ppb**  **Temperature,**  **F RH, %**  **Air Exchange, ACH LR**  **KIT BR**  **BMT AMB**  **LR KIT**  **BR BMT**  **AMB LR**  **2ND AMB**  **SF 6**  **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 4 3.2 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 (**

**H igh)**  Baseline 23.0 23.7 22.1 2 5.7 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 (**

**H igh)**  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.A- 7

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 L oading 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 l evels 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 Lo ading 1 versus Loadings 2 and 3 can be explained partly b y 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 Lo adings 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 emission s from aging wood products drives the concentration profile. For Loading 1, however, this profile is dampened by the relatively large mass being absorbed b y the wallboard sink in an “unloaded” state . Some of the difference in baseline values for Lo ading 1 versus Loadings 2 and 3 also may b e due to the relatively low humidity level at the time when baseline measurements were taken for Lo ading 1. 0 10 20 30 40 50 60 70 80

0 5 10 15 20 25 30 35**F o** **r m** **a l** **d e** **h y** **d e** **C o** **n c** **e n** **t r** **a t** **i o** **n ,** **p p** **b**

**Tim e**  **fr om**  **Lo ading**  **, da**  **ys Lo**  **ad ing** **1 Lo**  **ad ing** **2 Lo**  **ad ing** **3**A- 8

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 d uplicate DNPH samples indicated a combined sampling and analy tical 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 o f 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 woo d 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 emis sion 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 l ikely occurred during storage, even though products were wrapped in plastic. The elevated temperature in the warehouse may h ave accelerated the decay

process somewhat. **Table A** **- 4**  **. Computed Emission Rates for UF -**  **Bonded Products Loading**  **Emission Rate, μg/m 2**  **- h** 

**Underlayment Paneling**  **Cabinets Doors** 

**At Target ACH of 0.25 a**  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.A- 9

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 w eight 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. Inb oth 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 sec ond. Comparison of the theoretical (concentration s that would be expected in the absence of sinks) and measured concentrations indicate d that formaldehyde was adsorbed by the carpet , and the trend in the data appeared to reflect a first- order removal proce ss. Chamber tests for gy

psum 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 f rom these tests indicate d 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 ty pes of sinks. T ests to evaluate the behavior of underlay ment 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 underlay ment, carpet and padding. In the first test, a 7.1 - inch square piece of underlay

ment was placed in the pan with nothing above it. Inthe second test, a 7.1 - inch square piece of underlay

ment 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 indicate d that the underlay ment was releasing formaldehyde. While it was tempting to conclude from the results that the c arpet and padding had no effect on the emission of formaldehyde, the carpet/padding sink test described above indicate d otherwise.A- 10

**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 :  S ome logistical difficulties were encountered that prevented the study f rom being completed as outlined in the QAPP. Among the greatest difficulties were locating a study house and maintaining humidity l evels 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 associate d with house lo ading 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 success ively 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 e ffect of the gy psum 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 e stimate 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

p ainted gy

psum 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 hous e using a heat recovery

v entilator (HRV) was demonstrated. This ability w as 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 s ealing 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

**B.1 ANALYSIS BY MATTHEWS**  Prior work by

M atthews and colleagues at Oak Ridge National Laboratory during the mid- 1980s forms the primary

b asis 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 C ommission. One of these reports 63 included a sensitivity analys is 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 ; f or example, a sensitivity

of 0.1 would mean that a 10% change in the model is expected with a 10 0% change in the coefficient. The results of the sensitivity analys is 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 o f the analys is indicated that the concentration model was most sensitive to values for the coefficients representing the temperature and relative humidity (RH) dependence, regardless of product ty pe. 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** 64 Versar performed sensitivity analys is 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 analys is 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 f rom home both were set to zero for this analys is, 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 2 0 percent in each direction (i.e., 20 % lower and 20 % higher) from the b ase 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 c oncentration (ADC); (4) average daily dos e (ADD 65 ); 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** .

63 T. Matthews , T. Reed, B. Tromberg., K. Fung, C. Thompson, J. Simpson, and A. Hawthorne . 1985. Modeling and Testing of F

ormaldehyde Emission Characteristics of Pressed - Wood Products: Report XVIII to the U.S. Consumer Product Safety Commission . ORNL/TM - 9867, Oak Ridge Nati onal Laboratory, Oak Ridge, TN. 64 Extracted/adapted from F ormaldehyde from Composite Wood Products: Exposure Assessment. Draft Final Report. U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxi cs, Exposure Assessment Branch, 1200 Pennsylvania Avenue NW, Washington, DC 20460. July 2012. 65 The model output no longer includes ADD values.B - 2

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

**Input Parameter(s) Base V**  **alue(s)** Air Exchange Rate (ACH) 0.59 Emissions Half Life (years) 2.92 Temperature (°C) 23 Relative Humidity (%) 50 Source Loading Areas a (m2 ) 46, 59, 35, 4 Sink Loading Areas a (m2 ) 94, 420 House Age at Move - in (years) 5 Years Lived in H ouse 5 H ours in H ouse on Weekday, Weekend Day 15, 18 Inhalation Rate (m 3 /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 Conventio nal Home**  **Initial Conc in Zone 1,**  **mg/m 3**  **Conc 24 Months**

**Later in Zone 1, mg/m**  **3 Average Daily** 

**Concentration, mg/m**  **3 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.B - 3 **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

analys is. As with the conventional home, the background concentration and average concentration encountered when an individual is away f rom home both were set to zero for the analys is. 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 conc entration, a higher threshold (0.02 ppm) was used to examine the relative frequency o f 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** ).B - 4

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

**Input Parameter(s) Base Value(s)**  Air Exchange Rate (ACH) 0.5 0 Emissions Half Life (years) 2.92 Temperature (°C) 23 Relative Humidity (%) 5 0 Source Loading Areas a (m2 ) 95, 53, 26, 3, 43, 36 Sink Loading Areas a (m2 ) 72, 158 House Age at Move - in (years) 5 Years Lived in H ouse 5 H ours in H ouse on Weekday, Weekend Day 15, 18 Inhalation Rate (m 3 /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/m**  **3 Conc 24 Months** 

**Later in Zone 1,**  **mg/m 3**  **Average Daily**

**Concentration, mg/m**  **3 Average Daily** 

**Dose, mg/kg** **- day**  **% of Time**

**Conc entration**  **≥ 0.02 ppm** 0.1507 0.0937 0.0178 0.0033 35.0

**Figure B -** **2. Relative Model Sensitivity for the Manufactured Home**  **.** 0. 00% 10. 00% 20. 00% 30. 00% 40. 00% 50. 00% 60. 00% 70. 00% 80. 00% 90. 00% 100. 00% 

### Percent **Change i**  **n Mo**  **de l**  **Out put**  **D ue**  **t o**  **20 %**  **Change i**  **n Input V**  **al ue** 

Init ial Conc ent ra tion Conc @ 24 mo nt hs AD C AD D % Ti me ≥ 0 .0 2 ppm**Appendix C Basis f**  **or Emission Classes**C - 1

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 the se default values are described below, under the headings of Baseline Emissions Class ( **Section C.1**  ) and Reduced Emissions Classes ( **Section C.2**  ; includes C ARB 1, 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**  B etween 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 achiev e within the next three ye ars. These levels were weighted by production levels that mills reported in the survey to estimate average emission levels by c ertification 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 wo uld continue this product line after the CARB Phase 2 (CARB 2) effective date. b Hardwood plywood mills meeting CARB 2 and CARB Ultra Lo w 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.C - 2

**Table C -** **2. Formaldehyde Emissions Standards in the CARB Air Toxic Control Measure for Formaldehyde Emissions from Compressed Wood Products**  **a (ppm)**  **Emissions Standard HWPW**  **MDF Particleboard**  **CARB 1** 0.0 8 0.21 0.18 **CARB 2** 0.05 0.11 b 0.09 **CARB ULEF –**  **less frequent testing** 0.05 90% of samples < 0.06 All samples < 0.09 c 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 Com posite Wood Products Act (FSCWPA) emission limits are the same as the CARB 2 AT CM 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 prod

ucts, baseline emission levels were estimated separately f or 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 66 , a CARB Third Party C ertifier (TPC). Although PSIi s located in the U.S., the mills that it certifies are located mainly in Asia. 67 The mills certified by

P SIare located in countries that are major sources of pressed wood products imported into the United States; thus, the data from the PSIpresentation were assumed to represent emission levels from all non- Canadian CWPs imported into the U.S. The PSIpresentation included histograms of observed formaldehyde emission levels for hardwood ply

wood, MDF, and particleboard. The data included emission levels for 387, 198, and 193 samples of hardwood ply wood, MDF, and particleboard, respectively, and for all three product ty

pes combined. After imputing the data underlying these graphs, the average emission values reported in the presentation were successfully replicated. 68 This information was used to estimate the number of samples at different emission levels. 66 PSI. 2009. Professional Services Industries, Inc. (PSI). “The TPC Perspective,” available at http://university.ahfa.us/documents/f mhyde309_schutfort.pdf

. 67 According to CARB’s list of certified mi lls, as of Novem ber 12, 2010 , PSI wa s the TPC for 95 mills in 9 countries. The countries, and the number of mills certified by PSI in each, are as follows: Argentina (1) ; Chile (1) ; China (55) ; Ecuador (2) ; Indonesia (2) ; Malaysia (26) ; the Philippines (1) ; Taiwan (1) ; and Thailand (6). 68 The emission levels in the graphs seemed to be labeled according to the interval midpoints (e.g., a reported value of 0.05 ppm

represented an interval of 0.0375 to 0.075 ppm). The maximum values reported in the presentation for MDF and particleboard were used for the maximum intervals. The median value wa s used for the median interval for MDF. The data in the hardwood plywood graphic were consistent with an average value of 0.07 ppm rather than the 0.05 ppm value that could be calculated from the summary statistics shown in the presentation for all three product types com bined. For hardwood plywood, the three highest emission levels (all of which exceeded 1 .0 ppm) seemed to be driving this discrepancy; thus, they were dropped from the analysis. After dropping these outliers the im puted average emissions matched the 0.05 ppm value that could be calculated from the other summary statistics shown in the presentation.C - 3

The emission levels reported in the PSIpresentation ranged from near zero to levels exceeding the CARB 2 emission standards by asubstantial 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 2 0 13. 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 PSIdata that meet the CARB 2 limits. None of the intervals in the PSIdata 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 PSIdata 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 typ e were calculated (see **Table C -** **3** ). Although a number of samples in the PSIdata had emis sion levels close to zero, it was not possible to determine whether the products qualify f or certification as ultra low- emitting formaldehyde (ULEF) or no added formaldehyde (NAF) 69 ; the PSIpresentation did not identify the resin ty

pe 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 9 0% 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 PSIpresentation; thus, baseline emission levels were not estimated separately f or 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 ty pe 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 0.5 02 0.384 **CARB 2** 0.015 0.047 0.036 **Share of Imports None**  26% 11% 38% **CARB 2** 74% 89% 62%

69 Resin formulations that meet the NAF definition are those that do not contain any added formaldehyde in their formulation.C - 4

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 fol lows:  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 b e 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 ty pe of product, rather than one product that meets the California requirements and another ty

pe for the other 49 states). The fact that the samples were being tested for formaldehyde emissions by aCARB TPC suggests that many of them were produced b y 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 PSIdata 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 PSIpresentation 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

f iberboard, or veneer- core platform. The statutory definition goes on to state that laminated products are component parts used in the construction or assembly o f 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 ply wood 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 ply wood 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 ty pes, 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 b e similar to those from stock hardwood panel products before the ATCM went into effect.C - 5

For laminated products made outside the U.S. and Canada, average baseline emis sions were assumed to be the same as the levels for imported hardwood plywood that does not meet an emission standard (estimated from the PSIpresentation). Emissions data prior to the CARB ATCM are not available for non- Canadian imported hardwood plywo od. 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 ply wood 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. con sumption also is listed in the table for each product ty pe 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% 8 5.0% 1.9% --- --- **CARB ULEF** 4.2% 3.0% **CARB NAF** 16.2% 8.6% 7.1%C - 6

**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

– CARB 1, 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 Laminate d Products a All CWPs, including laminated products b , 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 Laminate d Products a,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 Laminate d Products at NAF As above, except that laminated products are assumed to meet NAF d standards. NAF, Including Laminated Products a 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 Laminate d 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 Laminate d Products Like CARB2 above, except that laminated products are not regulated as HWPW and, thus, are assumed remain at baseline emission levels. NAF, Excluding Laminate d 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. Inthe economic analys is 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 basi s) 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 Ply

wood and Veneer Association has indicated that laminated products represent about 30% of engineered wood flooring production. Therefore, this exposure analys is assumes that laminated pro ducts represent 30% of the volume of HWPW .C - 7

**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. Inc ompiling 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/analy tical option. As noted in a table footnote, for the CARB1 analy tical 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 Plywood**  **a 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) 0.058 b 0.058 --- 0.14 c 0.058 b 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 com ply with CARB1, even though producers reported that they were not intentionally meeting any particular standard. Because the baseline levels already com ply 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.C - 8

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 g enerally 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 unc ertainty . 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 analy tical option where CARB2/TSCA Title VIstatutory emission limits would be in effect. As with the CARB 1 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 70 of the same CWP ty pe 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 analy tical 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.

70 Emission levels for U.S. CARB2 - com pliant products (as opposed to non-U.S. products) were chosen because the data set from which average emission levels were determined was larger and, thus, considered more reliable.C - 9

**Table C -** **7. Emission Levels f or CARB2**  **Analytical Option by CWP Type, Origin, and Emissions Standard**  **Emissions Standard**  **Hardwood Plywood a**  **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 analy tical option whereb y 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 ty pe that are NAF - certified at baseline. For example, U.S. -pro duced 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.C - 10

**Table C -**  **8. Emission Levels for NAF Scenario by CWP Type, Origin, and Emissions Standard Emissions**  **Standard Hardwood Plywood**  **a 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** N

AF 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 no** **t 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 whereb y 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.C - 11

**Table C -**  **9. Emission Levels for CARB2 Scenario with Laminates at NAF by CWP Type, Origin, and Emissions Standard**  **Emis sions**  **Standard Hardwood Plywood**  **MDF Particleboard**  **Laminated Products**  **a 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**  C ARB2) 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. Con sumption**  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 - 12

**C.3 SLOPES AND INTERCEPTS FOR EMISSION RATES**  **Appendix D**  lists emission rates for various ty pes 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 s lope is a mass transfer coefficient that reflects the “backpressure” effect of the indoor formaldehyde concentration on the emission rate , whereas the intercept reflects the hy pothetical 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: [CH 2 O] SS = [CH

2 O] out + (CH

2 OER  * Area)/

Q (Eqn. C - 1) where: [CH

2 O] SS = steady- state formaldehyde concentration inside the

compartment (mg/m3 ) [CH 2 O] ou t = steady- state formaldehyde concentration outside the

compartment (mg/m3 ) CH 2 OER ’ = 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: CH 2 OER  = -m * [CH 2 O] V + b (Eqn. C - 2) where: m = the mass transfer coefficient (m/hr) [CH 2 O] V = the CH2 O concentration in the vapor phase (mg/m3 ) b = a constant; the emission rate at zero CH2 O concentration

in the air (mg/m2

-hr). Assuming that [CH 2 O] out is zero and that [CH 2 O] V = [CH

2 O] SS , and substituting Eqn. C - 2 into Eqn . C - 1, we can solve for b as follows:

b = [CH

2 O] SS * (1 + m * Area / Q) * (Q / A rea) (Eqn. C - 3 ) ASTM E 1333 , Standard Tes t Method for Determining Formaldehyde Concentrations in Air and Emission Rates from Wo od 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/m3 for PB, 0.95 m2/m 3 for HWPW , and 0.26 m2/m 3 for MDF. Using these rates along with an assumed slope (m ) for a given PWP ty pe, the corresponding intercept can be determined for a hy pothetical source that just meets a given emissions standard .C - 13

For example, the CARB2 emission standard for MDF is 0.11 ppm or 0.135 mg/m3

. An arbitrary chamber volume of 100 m 3 , together with a value of 50 m 3 /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; thi s 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 foll ows:

b = 0.135 mg/m3 * (1 + 1. 06 m/hr * 26m2 / 50 m3 ) * (50 m 3 / 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 ty pe as indicated in the table. **Table C -**  **10. Calculated Intercepts for Various Emission Levels for Each CWP Type Emission**  **Standard –**  **Origin Emission Level**  **a Assumed**  **Slope Calculated** 

**Intercept ppm**  **mg/m 3**  **m/hr mg/m**  **2 /hr**  **H ardwood 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. 0.0 58 0.0 72 0.27 0.0 57 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 * 1.23C - 14

Providing standard- specific slopes and intercepts for each CWP ty pe 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 ty pe yi elded identical modeling results to that from the more tedious a pproach 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 ty pe, 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**  **% P**  **articleboard** 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 ty pe in **Tabl e**  **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 ty pe.C - 15

**Table C -**  **12. Composite Intercepts by CWP Type and Emissions Scena rio**  **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 **P articleboard**  0.131 0.124 0.122 0.030 The modeling also accounted for some PWP ty pes that would not be subject to emission standards because they

are specifically exempt from TSCA Title VI . Underlay ment in homes ty pically is either tongue - and- groove softwood ply wood (SWPW) or oriented strand board (OSB). The emission rates from earlier chamber tests on S WPW are thought to be applicable to either type; for example, a study by H odgson et al. 71 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 k nown 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 rate s 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 underlay ment, interior doors, and coated CWPs are listed in **Table C -**  **13** . **Table C -**  **13. Emission Rates for Underlayment and Coated CWPs –**  **Baseline Scenario PW** **P Type/Class Proxy Used for Emission Rate**  **Slope Intercept**  Underlay ment (OSB) Softwood Ply wood (PF Resin) 0.61 0.03 0 Interior Doors & Coated CWPs a 6 -panel D oors Used in EPA Pilot Study 0.52 0.08 2

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

71 A.T Hodgson, A.F. Rudd, D. Beal, and S. Chandra. 2000. Volatile Organic Com pound Concentrations and Emission Rates in New Manufactured and Site -Built Houses. In door Air 10: 178 - 192.**Appendix D Historical Testing**  **o f P** **WP s**  **t o Derive Slope a** **nd Intercept Values**D - 1

**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 underlay ment  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 ply

wood (phenol - formaldehyde resin)  Hardboard (phenol - formaldehyde resin)  Kitchen cabinets  Interior doors. **D.2 DETAILED CHAMBER TESTING RESULTS**  **Table D**  **- 1**  72 lists , by

product ty

pe, 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 analys is 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 ty pe 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 Underlay ment, EPA- HWP for Hardwood Ply wood 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**).

72 The degree to which the historical data in Table D - 1 reflects current/recent domestic or imported production is not known.D - 2

**Table D -**  **1. Calculated Slopes and Intercepts for Matthews Model from Chamber Tests Conducted at 23**  **C, 50 % RH or at 25**  **C, 50 % RH a**  **(Liste d**  **Cases are for Conditions of 23**   **C and 50 % RH) Product Type**  **Product Code b**  **No. of Data Points**  **c N/L Range**  **d Me**  **asured Concentration**  **Range (ppm )**  **Matthew’s Emission Model e**  **ER = -**  **m (conc) + b Slope (m/hr)**  **Intcpt. (m g/m** **2 /hr)**  **R 2**  **Value f**  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 0.1 3 to 0.63

0.3 2 to 5.70 0.10 to 0.9 5 0.1 6 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 0.2 7 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 0.3 2 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 0.88D - 3

**Product Type Product Code**  **b No. of Data**  **Points c**  **N/L Range d**  **Me asured**  **Concentration Range (ppm** **) Matthew’s Emission Model**  **e ER =**  **- m (conc) + b**  **Slope (m/hr) Intcpt. (m** **g/m 2** **/hr) R** **2 Value**  **f** 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

0.81D - 4

**Product Type Product Code**  **b No. of Data**  **Points c**  **N/L Range d**  **Me asured**  **Concentration Range (ppm** **) Matthew’s Emission Model**  **e ER =**  **- m (conc) + b**  **Slope (m/hr) Intcpt. (m** **g/m 2** **/hr) R** **2 Value**  **f** 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 0.3 2 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 #1,2 g ORNL -PNP 3 #1,2 h 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 #1,2 g

ORNL -PND 1 #1,2 h ORNL -PND 3 #5 ORNL -PAN #1 4 4 3 4 0.15 to 0.35

0.12 to 1.06 0.3 2 to 1.11 0.1 4 to 0.9 5 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 0.1 1 0.13 0.36

0.81 0.90 0.85 Hardwood NBS -P6 - 1 8 0.04 to 1.91 0.022 to 0.253 0.12 0.05 0.83D - 5

**Product Type Product Code**  **b No. of Data**  **Points c**  **N/L Range d**  **Me asured**  **Concentration Range (ppm** **) Matthew’s Emission Model**  **e ER =**  **- m (conc) + b**  **Slope (m/hr) Intcpt. (m** **g/m 2** **/hr) R** **2 Value**  **f** Plywood Paneling (Unknown) NBS -P8 - 1

NBS -P10 - 1 NBS -P14 - 1 NBS -P17 - 1 NBS -P21 - 1 EPA-HWP 5 11 8 5 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 0.027 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

0.45 0.67 0.52 0.22 0.96 0.04

0.30 0.08 0.15 0.03 0.16 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

G eorgia 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 mo del parameters for the tested boards; Matthews mo del parameters for these products were calculated from the HBF mo del parameters. The NBS report listed Matthews mo del 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 reporte d 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" f ollowed by

adigit 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 - 6

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 m 2 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 m 2 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 W ood 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. 19 87. Effect of Ventilation and Loading Rates in Large Chamber Testing of Formaldehyde Emissions from Com posite Panels. Forest Products Journal 37(4):31 - 37.D - 7

**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 ty pes 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 hy

pothetical 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 a**  **nd Intercepts for Eight Product Types** 

**Product Type Average Slope**  **Average Intercept** Particleboard Underlay

ment 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 ty

pes 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 m 3 ) and the product loading ratio was 0.13 ft2/ft3 (0.43 m2/m 3 ). **Table D -** **3 .**  **Chamber Conditions and**  **Test Results for Kitchen Cabinets –**  **EPA Pilot Study Air Exchange**  **Rate, ACH Temperature,** 

**°F RH,** 

**% Chamb**  **er Concentration, mg/m** **3 Calculated Emission**  **Rate, mg/m 2**  **- 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 0.0452D - 8

As shown in the table, the increase in the chamber concentration was less than proportional to the de crease in air exchange rate. For example, if there were no dependence of the emission rate on the air concentration (i.e., if there were no “backpressure” effect), then one would expect a six - fold decrease in the air exchange rate (from 1.0 to 0.17 ACH) to result in a six - fold increase in the concentration (from 0. 035 to 0. 212 mg/m3 ); however, the measured chamber concentration at 0.17 ACH (0.114 mg/m3 ) was about half the expected value, indicative of a backpressure effect. The emission rates shown in the table were calculated under a steady- state assumption as follows: ER = (C

ss * AER * V) / Area (D - 1) Where: ER = Emission rate, mg/m2

-hr C ss = Steady- state concentration, mg/m3 AER = Air exchange rate, 1/hr V = Chamber volume, m3 Area = Exposed surface area, m2 = loading ratio (m2/m 3 ) * chamber volume (m3 ) The volume term appears in both the numerator and denominator; thus, Eqn. D - 1 can be simplified to: ER = (C

ss * AER) / L (D - 2) Where: L = Loading ratio, m2/m 3 The calculated emission rate is then regressed against the chamber concentration, as follows: ER = -m * Css + b (D - 3 ) Where: m = Regression slope (reflecting the backpressure effect) b = Regression intercept The resultant regression estimates from this procedure are 0.49 for the slope and 0.10 for the intercept. The regression intercept obtained here is slightly different from that shown in **Table D**  **- 1**  (0.08), but there is uncertainty as to the specific data points that were used by the originating researchers. A comparison of the predicted and calculated emission rates ( **Table D -** **4** ) indicates a relatively high degree of correspondence, as reflected in an R2 value of 0.94 for the regression. **Table D -** **4. Predicted vs. Calculated Emission R** **ates for Kitchen Cabinets –**  **EPA Pilot S tudy**  **Air Exchange Rate, ACH**  **Temperature,**

**°F RH,** 

**% Predicted Emission** 

**Rate, mg/m 2**  **- hr**  **Calculated Emission Rate, mg/m** **2 -**  **hr** 1.00 75.0 50 0.0861 0.0821 0.51 77.5 48 0.0719 0.0765 0.17 77.5 51 0.0475 0.0452**Appendix E Derivation of Tw**  **o -** **zone Steady -**  **state Solution**E - 1

Mass b alance e quation for z one 1 (well -mixed assumption) :

1 1 12 1 10 2 21 0 01 1 1 S C Q C Q C Q C Q dt dC V      (1) where:

1 1 1 1 y C z S    (Matthew’s implementation) (2)

1 1 1 1 Area m z Zone in sources num k k 

## 

  m 3 /hr (3)

k Zone in sources num k k Area b y 

# 

  1

1 1 mg/hr (4)

m = mass transfer coefficient, m/hr b = emission rate when the air concentration is zero, mg/(m2 hr) Q = flow rates, m3 /hr C = concentrations, mg/m3 Area = emission area, m2 t = time, hr V = volume, m3 Mass b alance e quation for z one 2 (well -mixed assumption):

2 2 21 2 20 1 12 0 02 2 2 S C Q C Q C Q C Q dt dC V      (5) where: Q 1 2 Q 2 1

Q 01 Q 0 2 Q 10 Q 2 0 Zone 1 V 1 S 1 Zone 2 V2 S 2E - 2 2 2 2 2 y C z S    (6)

2 2 1 2 Area

Z m z Zone

in sources num k k   

## 

 (7)

2 2 1 2 C m y Zone

in sources num k k 

## 

  (8) Assume flows are constant and set dC/dt = 0 (steady state condition):

1 1 1 1 12 1 10 2 21 0 01 0 y C z C Q C Q C Q C Q       (9) And: 2 2 2 2 21 2 20 1 12 0 02 0 y C z C Q C Q C Q C Q       (10) Solving for C 1 :

1 12 10 1

2 21 0 01 1 z

Q Q y C Q C Q C 

    (11) Solving for C 2 :

2 21 20 2

1 12 0 02 2 z

Q Q y C Q C Q C 

    (12) Substitute e quation 12 into e quation 1 1 :

1 12 10 1 2 21 20 2

1 12 0 02 21 0 01 1 z

Q Q y

z Q Q y C Q C Q Q C Q C 

 

            

 (1 3 )E - 3

Rearranging and combining terms: 

##   2 21 20 2 21 1 12 21 0 02 21 1 0 01 1 1 12 10 z Q Q y

Q C Q Q C Q Q y C Q C z Q Q          

##       2 21 1 12 21 0 02 21 2 21 20 1 0 01 1 1 12 10 y Q C Q Q C Q Q z Q Q y C Q C z Q Q         

2 21 1 12 21 0 02 21 1 2 1 21 1 20 0 2 01 0 21 01 0 20 01 1 2 1 1 21 1 1 20 1 1 2 12 1 21 12 1 20 12 1 2 10 1 21 10 1 20 10 y Q C Q Q C Q Q y

z y Q y Q C z Q C Q Q C Q Q C z z C Q z C Q z C z Q C Q Q C Q Q C z Q C Q Q C Q Q    

             

##  

    2 21 1 2 21 20 0 02 21 2 01 21 01 20 01 1 2 1 21 1 20 1 2 12 20 12 2 10 21 10 20 10 y Q y z Q Q C Q Q z Q Q Q Q Q C z z Q z Q z z Q Q Q z Q Q Q Q Q                

##       2 1 21 1 20 1 2 12 20 12 2 10 21 10 20 10 2 21 1 2 21 20 0 02 21 2 01 21 01 20 01 1 z z Q z Q z z Q Q Q z Q Q Q Q Q y Q y z Q Q C Q Q z Q Q Q Q Q C                (1 4 ) Similarly : 

##    

  1 2 12 2 10 2 1 21 10 21 1 20 12 20 10 20 1 12 2 1 12 10 0 01 12 1 02 12 02 10 02 2 z z Q z Q z z Q Q Q z Q Q Q Q Q y Q y z Q Q C Q Q z Q Q Q Q Q C                (1 5 )