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REVISED TECHNICAL REPORT 

Measuring Formaldehyde Emissions from Low Emitting Hardwood Plywood 

Panels under Different Conditions of Temperature and Relative Humidity 

prepared for

U.S. Environmental Protection Agency

Office of Pollution Prevention and Toxics

National Program Chemicals Division 

under

Contract EP-W-09-024

Work Assignment 3-03

by

Battelle

Columbus, Ohio

April 8, 2013
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Acknowledgments

The work described in this report was conducted by Battelle under the direction of the U.S. 

Environmental Protection Agency through Work Assignments 2-07 and 3-03 of EPA Contract 

EP-W-09-024. 
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Contents

Acknowledgements ....................................................................................................................... ii

List of Abbreviations .................................................................................................................... v

Chapter 1 Executive Summary ...................................................................................................... 1

Chapter 2 Background ................................................................................................................... 3

Chapter 3 Test Design and Procedures.......................................................................................... 5

3.1 Project Goals and Experimental Design ...............................................................................5

3.1.1 Large/Small Chamber Test Comparison............................................................... 5

3.1.2 Small Chamber Emissions Testing ....................................................................... 6

3.2 Test Materials....................................................................................................................8

3.3 Experimental Methods..........................................................................................................8

3.3.1. Large Chamber Tests ............................................................................................ 8

3.3.2 Small Chamber Tests ............................................................................................ 8

3.3.3 Chromotropic Acid Analysis................................................................................. 9

Chapter 4 Quality Assurance/Quality Control............................................................................. 10

4.1 Chamber Test Conditions ...................................................................................................10

4.2 Chromotropic Acid Calibration ..........................................................................................10

4.3 Chamber HCHO Background.............................................................................................11

Chapter 5 Statistical Methods...................................................................................................... 12

5.1 Large/Small Chamber Test Comparison.............................................................................12

5.2 Small Chamber Emission Tests..........................................................................................12

Chapter 6 Test Results................................................................................................................. 13

6.1 Large/Small Chamber Comparison ....................................................................................13

6.2 Small Chamber Emissions Tests.........................................................................................14

6.2.1 Effect of Resin Type on HCHO Emissions......................................................... 15

6.2.2 Effect of Temperature on HCHO Emissions....................................................... 18

6.2.3 Effect of Relative Humidity on HCHO Emissions............................................. 18

6.2.4 Characterization of Measurement Variability Inherent to Small Chamber Testing

............................................................................................................................. 19

Chapter 7 Summary and Conclusions.......................................................................................... 20

Chapter 8 References................................................................................................................... 22

Appendix A ................................................................................................................................ 24

Appendix B.................................................................................................................................. 29
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Tables

Table E-1. Comparison of HCHO Emissions of Three Hardwood Plywood Panel Types at 

Lowest and Highest Temperature and Relative Humidity Conditions........................................... 2

Table 1. Test Matrix and Order of Testing for Small Chamber Tests. ........................................... 7

Table 2. Results of Large/Small Chamber Comparison with ULEF-UF HWPW....................... 13

Table 3. Test Conditions and HCHO Results from Small Chamber Tests................................... 14

Table 4. Estimates and Standard Errors from Regression Model................................................ 17

Table 5. Summary of Temperature and Relative Humidity Effects on Formaldehyde Emissions 

from Three Types of Hardwood Plywooda................................................................................... 17

Table 6. Comparison of HCHO Emissions of Three Hardwood Plywood Panel Types at Lowest 

and Highest Temperature and Relative Humidity Conditions...................................................... 21

Figures

Figure 1. HCHO Emissions vs. RH for T=25 °C and T=30 °C................................................... 15
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List of Abbreviations

ASTM ASTM International, formerly American Society for Testing and Materials

ATCM Airborne Toxic Control Measure

°C degrees Celcius 

CARB California Air Resources Board

EPA U.S. Environmental Protection Agency

HCHO formaldehyde

HWPW hardwood plywood

m

2

/m3 meters squared/meters cubed

MDF medium density fiberboard

g micrograms

g/mL micrograms per milliliter 

mL milliliters

MUF melamine-urea-formaldehyde

NAF no added formaldehyde

NAF-acrylic no-added formaldehyde – acrylic resin

PB particleboard

pMDI polymeric diphenylmethane diisocyanate 

ppm parts per million 

RH relative humidity

SD standard deviation

T temperature

TPC third party certifier

TSCA Toxic Substances Control Act

ULEF ultra low-emitting formaldehyde

ULEF-UF ultra low-emitting formaldehyde-urea-formaldehyde

ULEF-PF ultra low-emitting formaldehyde- phenol-formaldehyde
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Chapter 1

Executive Summary

In July of 2010, the Formaldehyde Standards for Composite Wood Products Act, or Title VI of 

the Toxic Substances Control Act (TSCA), was signed into law. The statute establishes 

formaldehyde emission standards for hardwood plywood (HWPW), medium density fiberboard 

(MDF), and particleboard (PB) sold, supplied, offered for sale, or manufactured in the United 

States. These emission standards are identical to the Phase 2 standards established by the 

California Air Resources Board’s (CARB) Airborne Toxic Control Measure (ATCM), which 

applies to products offered for sale, supplied, or manufactured for use in California. TSCA Title 

VI requires EPA to promulgate regulations implementing the emission standards as well as a 

number of other provisions. The statute also specifically directs EPA to consider provisions for 

ultra low-emitting formaldehyde (ULEF) resins and no-added formaldehyde (NAF) resins.

Both TSCA Title VI and the CARB ATCM require formaldehyde emission testing to be 

conducted quarterly using the ASTM, International (formerly American Society for Testing and 

Materials (ASTM)) E1333 large chamber method or ASTM D6007 small chamber method. The 

CARB ATCM requires manufacturers of the regulated wood products to demonstrate 

compliance with the emission standards by having their product emission tests and quality

control processes certified by a third-party certifier (TPC). Under the CARB ATCM, 

manufacturers who use NAF and ULEF resins may qualify for reduced testing requirements

and/or an exemption from TPC certification requirements, with renewal of that status required 

every two years. Under both CARB ATCM and TSCA Title VI definitions, a NAF composite 

wood product cannot incorporate a resin made with formaldehyde, and a ULEF composite wood 

product is one made from resins that may contain formaldehyde, but emit it at particularly low 

levels as specified in the definitions. 

Recent testing has suggested that some ULEF composite wood products may have significantly 

increased formaldehyde emissions when the temperature (T) and/or relative humidity (RH) are 

higher than the standard conditions (i.e., 25 degrees Celsius (°C) and 50 %RH) required in the 

ASTM E1333 and D6007 test methods. Consequently, EPA initiated testing to assess the effect 

of elevated T and RH conditions on formaldehyde emissions from NAF and ULEF composite 

wood products. Specifically, formaldehyde emissions from HWPW panels made with NAFacrylic, ULEF-PF (phenol-formaldehyde), and ULEF-UF (urea-formaldehyde) resins were

determined using standard methods by a CARB-approved TPC laboratory at several T and RH 

conditions, with sufficient repetition to assess the consistency of the test results. In addition to 

testing at the standard T/RH conditions, each HWPW type (i.e., HWPW made with the three 

different resins) was tested at 25 °C with 70 and 85 %RH, and at 30 °C with 50, 70, and 85

%RH. At each T/RH condition three emission tests were conducted on each HWPW type

simultaneously using the ASTM small chamber (D6007) method. The test results were 

evaluated to determine the effect of T and RH on the formaldehyde emissions of HWPW panels 

made with each of the three resins. 

The analysis of test data showed that formaldehyde emissions from the ULEF-UF panels

increased with increasing T and RH, and that this relationship was statistically significant with 
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respect to the panels selected for the experiment (see Appendix for further details on the 

statistical analyses). For the NAF-acrylic panels, the analysis showed a small increase in 

formaldehyde emissions with increasing T and RH, but this relationship was not statistically

significant with respect to the panels selected for the experiment. Formaldehyde emissions for 

the ULEF-PF panels decreased slightly with increased T and RH, and this relationship was found 

to be statistically significant with respect to the panels selected for the experiment. For each 

resin type, testing at all T and RH conditions was conducted with samples from the same panels, 

so that any effects specific to the panels (e.g., location in stack, manufacturer’s lot) apply equally 

to all observations across T and RH. Time (i.e., product aging during the sequence of tests) is 

also unlikely to have influenced the results, since the T and RH conditions used in testing were in 

random order. 

 

Table E-1 illustrates the results of this study. For each panel type used in the study, Table E-1 

reports the estimated formaldehyde (HCHO) emission at the standard testing conditions (25 

°C/50 %RH) and at the highest T and RH conditions (30 °C/85 %RH), based on the statistical 

analysis of all test results for that panel type. Table E-1 also shows the change in HCHO 

emissions between the standard testing conditions and the highest conditions. 

Table E-1. Comparison of Estimated HCHO Emissions of Three Hardwood Plywood Panel 

Types at Lowest and Highest Temperature and Relative Humidity Conditions 

HWPW 

Panel Type

HCHO Emission

at 25 °C/50 %RH 

(ppm)

HCHO Emission 

at 30 °C/85 %RH

(ppm)

Change

(ppm)

ULEF-UF 0.0471 0.1230 0.0759

ULEF-PF 0.0356 0.0333 -0.0023

NAF-acrylic 0.0238 0.0290 0.0052

Note: TSCA Title VI requires no test result higher than 0.05 ppm (under standard T and RH conditions) for HWPW made 

with ULEF resins to qualify for a TPC exemption.

Table E-1 shows that the combined effect of T and RH resulted in an increase in formaldehyde 

emission of the ULEF-UF panels by 0.0759 parts per million (ppm) between the standard 

conditions of 25 °C/50 %RH and the test conditions of 30 °C/85 %RH. The HCHO emissions 

from the ULEF-PF panels decreased by 0.0023 ppm between the standard conditions and 30 

°C/85 %RH. The HCHO emissions from the NAF-acrylic panels increased by 0.0052 ppm 

between the standard conditions and the test conditions of 30 °C/85 %RH.

The results of this study showed that HWPW panels made with ULEF-UF resin had a greater 

response to T and RH than either the NAF-acrylic or the ULEF-PF panels. Statistical tests 

showed that the response of HCHO emission to T and RH for the ULEF-UF panels used in the 

experiment was significantly different from that of the NAF-acrylic and ULEF-PF panels. The 

observed emission behavior of the three different types of HWPW in this study is consistent with 

the nature of the resins used in their manufacture. The minimal emissions and absence of T and 

RH effects with the NAF-acrylic panels reflect the absence of HCHO in the NAF resin, and the 

differences in emissions and T and RH effects for the ULEF-UF and ULEF-PF panels are 

consistent with the greater chemical stability of the PF resin relative to the UF resin against 

degradation by moisture.

 
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Chapter 2

Background

In 2007, the California Air Resources Board (CARB) issued an Airborne Toxic Control Measure 

(ATCM)1to reduce formaldehyde (HCHO) emissions from hardwood plywood (HWPW), 

medium-density fiberboard (MDF), and particleboard (PB). On July 7, 2010 the Formaldehyde 

Standards for Composite Wood Products Act, or Title VI of the Toxic Substances Control Act 

(TSCA), 15 U.S.C. 2697 was signed into law.

2

 The statute establishes HCHO emission 

standards for HWPW, MDF, and PB sold, supplied, offered for sale, or manufactured in the 

United States. These emission standards are identical to the CARB ATCM Phase 2 standards. 

TSCA Title VI also requires EPA to promulgate regulations that include provisions on labeling; 

chain of custody requirements; sell-through provisions; finished goods; third-party testing and 

certification; auditing and reporting of third-party certifiers; recordkeeping; enforcement; 

laminated products; and exceptions from regulatory requirements for products and components 

containing de minimis amounts of composite wood products. The statute also specifically directs 

EPA to consider provisions for ultra low-emitting formaldehyde (ULEF) resins and no-added 

formaldehyde (NAF) resins.

TSCA Title VI and the CARB ATCM both define NAF-based and ULEF-based resins in terms 

of the composition of the resin system and the maximum HCHO emissions for composite wood 

products made with these resin systems. In general, a NAF composite wood product cannot 

incorporate a resin formulated with HCHO. A ULEF composite wood product is one made from 

resins that may contain HCHO, but that emit it at particularly low levels. TSCA Title VI and the 

CARB ATCM define identical statutory maximum emissions for products made with NAF or 

ULEF resins. 

The CARB ATCM and TSCA Title VI require manufacturers of the regulated composite wood 

products to demonstrate compliance with the emission standards by emission testing, conducted 

quarterly using the ASTM, International (formerly American Society for Testing and Materials 

(ASTM)) E1333 large chamber method,

3

or the ASTM D6007 small chamber method4 with a 

showing of equivalence with ASTM E1333. Other methods can be used for quality control 

testing, but these methods must be shown to be equivalent or to correlate with the ASTM E1333 

method. Under the CARB ATCM, manufacturers who use NAF or ULEF resins may be

provided with incentives, such as reduced testing and/or exemption from third-party certification 

requirements.

Recent testing5,6 has suggested that some composite wood products may have increased HCHO

emissions when the temperature (T) and/or relative humidity (RH) are higher than the standard 

test conditions (i.e., 25 °C and 50 %RH) required in the ASTM test methods.3,4 Frihart et al.5

tested HCHO emissions from small pieces of HWPW panels made with ULEF-UF resin and a 

soy-based NAF resin at 25 and 35 °C and RH conditions of 30, 75, and 100 %. They reported 

increases in HCHO emissions from the ULEF-UF material at elevated T and RH conditions. In

that study HCHO emissions were determined using a modified test method, EN 717-3 (Flask 

Method), which is difficult to compare with ASTM E-1333. In response to the Frihart et al. 
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study, Riedlinger et al.6determined HCHO emissions from four types of PB panels (made with 

UF, PF, melamine-urea-formaldehyde (MUF), and polymeric diphenylmethane diisocyanate

(pMDI)) resins, one of which (the PF product) was certified as a ULEF panel under the CARB 

ATCM. Emissions were determined at multiple time points at both the standard T/RH

conditions and at 30 °C/75 %RH using the small chamber test method (ASTM D6007)4and the 

Dynamic Microchamber Method7for up to 50 days. Aspects of the testing confound 

comparisons of the data; for example, testing at the standard and elevated T/RH conditions was 

conducted in two different laboratories, using different sampling procedures and analytical 

methods, with sampling at different time points.6 Nonetheless, the study appears to show that 

HCHO emissions from panels made with all four resin types increased by factors of 2 to 3 under 

the elevated T/RH conditions. Emissions from panels made with two non-UF resin types (i.e., 

PF and pMDI) never exceeded the numerical emission limit of 0.09 parts per million (ppm) for 

PB, even at elevated conditions, whereas emissions from panels made with the UF resins (i.e., 

UF and MUF) exceeded that numerical emission limit at elevated T and RH until about 20 or 25 

days after the start of the testing. 

In addition to the recent studies discussed above, a number of older studies have demonstrated

that UF resins have increased HCHO emissions under conditions of elevated temperature and 

humidity. For example, a 1985 review article8analyzed data from numerous studies from 1960-

1984 on the effects of temperature or humidity on HCHO emissions from UF bonded PB and 

HWPW. This article concluded that HCHO emissions increased exponentially with increasing 

temperature. The relationship between humidity and HCHO emissions was more complex and 

variable, but the author concluded that the relationship was approximately linear.

Because of the collective evidence that composite wood panels made with UF resins may have 

increased HCHO emissions under conditions of elevated temperature and humidity, EPA 

initiated this study as part of EPA’s effort to consider whether or what type of ULEF provisions 

to include in regulations implementing TSCA Title VI. The purpose of this study was to assess 

the effect of elevated T and RH conditions on HCHO emissions from NAF and ULEF composite 

wood products made with various resins. This study was designed to use ASTM standard 

chamber test methods conducted by a CARB-approved TPC laboratory to determine HCHO 

emissions at several T and RH conditions with sufficient repetition to assess the consistency of 

test results. Subsequent chapters of this report describe the test procedures, data quality,

statistical analysis, and HCHO emission results from the testing.
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Chapter 3

Test Design and Procedures

3.1 Experimental Design 

Veneer core HWPW panels manufactured using each of three different resin types, NAF-acrylic, 

ULEF-PF , and ULEF-UF, were tested. The HCHO emissions of each type of HWPW were 

measured at three different RH conditions (i.e., 50, 70, and 85 %RH) at each of two different T 

values (i.e. 25 °C and 30 °C). Thus the HCHO emissions were characterized at the standard 

conditions of 25 °C and 50 %RH required by the ASTM methods E1333 and D6007, and at 

higher conditions of T and/or RH.

The testing to characterize HCHO emissions was conducted by PFS Corporation (Cottage Grove, 

WI), a TPC testing laboratory approved by CARB

(http://www.arb.ca.gov/toxics/compwood/listoftpcs.htm). Testing of the HWPW panels made 

with three different resin types was carried out in small chambers according to the ASTM D6007

method, as described below. A limited comparison was also conducted of the HCHO emission 

results from the D6007 small chamber method to those of the E1333 large chamber method. 

That comparison was conducted with ULEF-UF HWPW panels at two T/RH conditions 

representing the extremes of the test matrix (i.e., 25 °C/50 %RH and 30 °C/85 %RH). In all 

testing, gas-phase HCHO was quantified using the chromotropic acid method as described in the 

E1333 and D6007 methods. Note that the HCHO emission results reported in this document are 

as measured at the applicable designated test conditions, i.e., no adjustment to standard 

conditions (e.g., using the Berge equations cited in the ASTM methods)

3,4 was made.

The results of this study were used to (1) determine whether HCHO emissions were statistically 

significantly affected by elevated T/RH conditions relative to emissions at the standard

conditions of 25 °C/50 %RH, (2) determine whether HCHO emissions and any T/RH effects 

were statistically significantly different between HWPW panels of different resin types, and (3) 

characterize the measurement variability inherent to the small chamber testing.

3.1.1 Large/Small Chamber Test Comparison

The CARB ATCM and TSCA Title VI emission standards are based on the ASTM E1333 test 

method, and the CARB ATCM requires TPCs to demonstrate on an annual basis that HCHO 

emission results obtained using the ASTM D6007 method are equivalent to those obtained using 

the E1333 method. Requirements for that equivalency demonstration include comparison of at 

least 10 sample sets, with each sample set including nine panel samples tested by the D6007 

method in groups of three with the results averaged together, and inclusion of at least five 

samples sets in each of at least two emission ranges defined by CARB.1 The TPC used in this 

project successfully conducted such an annual equivalency test according to the CARB ATCM

§93120.9 (a)(2)(B),

1

on July 31, 2012, shortly before the start of testing for this study.

An additional comparison of the large and small chamber methods was conducted in this study, 

by emission testing of HWPW made with ULEF-UF resin at standard conditions (T = 25°C, RH 

= 50 %), and at elevated T/RH conditions (T = 30 °C, RH = 85 %). In this comparison, the 
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procedures of the E1333 and D6007 methods were followed, with specific minor exceptions that 

are noted below and/or described in Section 3.3. In using both methods, care was taken to 

maintain low chamber background HCHO concentrations. To accurately determine HCHO 

background concentrations, the TPC laboratory prepared HCHO standards for the chromotropic 

acid method at lower concentrations than those specified in the ASTM methods,

3,4 and prepared 

a calibration curve that included those additional calibration points. The ULEF-UF HWPW test 

material was conditioned for 7 days before testing in the large chamber as required by the E1333 

method; the conditioning period was 48 hours in the D6007 small chamber testing, considerably 

longer than the minimum of 2 hours required for that method. This extended conditioning period 

was chosen to assure that the HWPW was completely equilibrated to the elevated T and RH 

conditions. 

For the additional comparison of large (E1333) and small (D6007) chamber methods, a single 

sample of the ULEF-UF HWPW was tested for HCHO emission in the large chamber at each of 

the two test conditions noted above. Duplicate air samples were drawn from the large chamber 

for determination of the HCHO concentration using the chromotropic acid method, and the 

average of those duplicate sample results was reported as the HCHO emission result. For the 

small chamber comparison tests, three small specimens (3 in × 7 in) were cut from the interior of 

each of three separate 4 feet × 8 feet panels of the ULEF-UF HWPW panels. The nine resulting 

specimens (three specimens from each of the three panels) were then conditioned together at the 

test conditions of T and RH. After conditioning, the nine specimens were distributed into three 

identical small test chambers so that each chamber contained one specimen from each of the 4 

feet × 8 feet panels. Thus, each chamber contained identical sets of test specimens. The three 

small chamber tests were carried out simultaneously. Triplicate air samples were drawn from 

each of the three small chambers for determination of the HCHO concentration using the 

chromotropic acid method, and the average of the triplicate sample results from each chamber 

was reported as the HCHO emission result from that chamber. 

3.1.2 Small Chamber Emissions Testing

Small chamber (D6007) emissions testing was performed to characterize HCHO emission from

each of the three types of HWPW panels (i.e., HWPW panels made with three different resins) at 

each of the six specific T/RH conditions. For each combination of HWPW panel type and T/RH 

condition, triplicate tests were conducted simultaneously in three small test chambers. Thus with 

triplicate testing of three HWPW panel types at two T levels and three RH levels, a total of 3 × 3 

× 2 × 3 = 54 discrete small chamber tests were conducted, 18 on each of the three HWPW panel 

types. Cutting of test specimens, sample conditioning, and HCHO sampling for the small 

chamber tests were performed as described in Section 3.1.1.

The test matrix for the small chamber testing is shown in Table 1. For each day of testing, Table 

1 shows the HWPW panel type tested as well as the nominal T and RH test conditions. Table 1 

also includes a running number of all the tests (up to 54 total), and indicates the triplicate tests of 

a single HWPW panel that were run on a single test day. Table 1 shows the small chamber tests
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Table 1. Test Matrix and Order of Testing for Small Chamber Tests.

Test 

Day Test #

HWPW 

Resin Type Temperature

Relative 

Humidity

Replicate 

#

Test 

Day Test #

HWPW

Resin Type Temperature

Relative 

Humidity

Replicate 

#

1

1 NAF-acrylic 25 °C 50 % 1

10

28 NAF-acrylic 25 °C 70 % 1

2 NAF-acrylic 25 °C 50 % 2 29 NAF-acrylic 25 °C 70 % 2

3 NAF-acrylic 25 °C 50 % 3 30 NAF-acrylic 25 °C 70 % 3

2

4 ULEF-PF 25 °C 50 % 1

11

31 ULEF-PF 25 °C 85 % 1

5 ULEF-PF 25 °C 50 % 2 32 ULEF-PF 25 °C 85 % 2

6 ULEF-PF 25 °C 50 % 3 33 ULEF-PF 25 °C 85 % 3

3

7 ULEF-PF 30 °C 70 % 1

12

34 ULEF-PF 30 °C 85 % 1

8 ULEF-PF 30 °C 70 % 2 35 ULEF-PF 30 °C 85 % 2

9 ULEF-PF 30 °C 70 % 3 36 ULEF-PF 30 °C 85 % 3

4

10 NAF-acrylic 30 °C 70 % 1

13

37 ULEF-UF 25 °C 50 % 1

11 NAF-acrylic 30 °C 70 % 2 38 ULEF-UF 25 °C 50 % 2

12 NAF-acrylic 30 °C 70 % 3 39 ULEF-UF 25 °C 50 % 3

5

13 ULEF-PF 30 °C 50 % 1

14

40 ULEF-UF 30 °C 70 % 1

14 ULEF-PF 30 °C 50 % 2 41 ULEF-UF 30 °C 70 % 2

15 ULEF-PF 30 °C 50 % 3 42 ULEF-UF 30 °C 70 % 3

6

16 NAF-acrylic 30 °C 50 % 1

15

43 ULEF-UF 30 °C 85 % 1

17 NAF-acrylic 30 °C 50 % 2 44 ULEF-UF 30 °C 85 % 2

18 NAF-acrylic 30 °C 50 % 3 45 ULEF-UF 30 °C 85 % 3

7

19 NAF-acrylic 30 °C 85 % 1

16

46 ULEF-UF 30 °C 50 % 1

20 NAF-acrylic 30 °C 85 % 2 47 ULEF-UF 30 °C 50 % 2

21 NAF-acrylic 30 °C 85 % 3 48 ULEF-UF 30 °C 50 % 3

8

22 NAF-acrylic 25 °C 85 % 1

17

49 ULEF-UF 25 °C 85 % 1

23 NAF-acrylic 25 °C 85 % 2 50 ULEF-UF 25 °C 85 % 2

24 NAF-acrylic 25 °C 85 % 3 51 ULEF-UF 25 °C 85 % 3

9

25 ULEF-PF 25 °C 70 % 1

18

52 ULEF-UF 25 °C 70 % 1

26 ULEF-PF 25 °C 70 % 2 53 ULEF-UF 25 °C 70 % 2

27 ULEF-PF 25 °C 70 % 3 54 ULEF-UF 25 °C 70 % 3
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in the chronological order in which they were conducted; due to product availability, testing with 

the ULEF-UF panels was conducted after testing with the NAF-acrylic and ULEF-PF panels had 

been completed.

3.2 Test Materials

The HWPW panels used for testing were labeled as NAF or ULEF as per the CARB ATCM and 

were obtained from major manufacturers who were known to the test laboratory or to EPA as 

potential sources of such products. Each manufacturer identified the resin type used in their 

product. All three panel types were 5-ply veneer core HWPW; the NAF-acrylic and ULEF-PF

panels were 9 millimeters thick, and the ULEF-UF panels were 0.5 inch thick. All materials were 

obtained as stacks of 4 feet × 8 feet panels, sandwiched between additional panels of the same 

material and wrapped in plastic film. Panels used for testing were taken from the interior of the 

stack. All panels and cut test pieces were kept wrapped in storage at ambient conditions at the 

TPC laboratory until withdrawn for conditioning at test conditions. 

ULEF-UF panels from two different manufacturers were tested because the first panels tested 

showed emissions in initial small chamber tests that did not meet the ULEF emission standards. 

The emission testing results from those panels are described in Appendix B. ULEF-UF HWPW 

panels were obtained from a different manufacturer and were subjected to the full matrix of 

testing; the results from those ULEF-UF panels are presented in the body of this report.

 

3.3 Experimental Methods

3.3.1. Large Chamber Tests 

With the exception of the elevated T and RH condition used in the comparison to the small 

chamber test, the large chamber test procedure (ASTM E1333) was used as published,3 with a 

product loading ratio of 0.43 meters squared/meters cubed (m

2

/m

3

) as designated in the method 

for HWPW panels. The large chamber volume was 22.9 m3(810 cubic feet) with an air 

exchange rate of 0.5/hour. The T and RH in the test chamber were monitored and recorded at 5-

minute intervals throughout the large chamber tests, and those data are summarized in Section 4 

of this report.

3.3.2 Small Chamber Tests

With the exception of the elevated T and RH conditions used in most tests, the small chamber 

test procedure (ASTM D6007) was used as published,4 with an area-specific air flow rate (N/L) 

of 1.173 meters/hour, as designated for HWPW panels. This equates to a 0.5/hour air exchange 

rate with the small chamber volume of 0.196 m3(6.92 cubic feet). The T and RH in the test 

chambers were monitored and recorded at 1-minute or 5-minute intervals throughout the small 

chamber tests, and those data are summarized in Section 4 of this report. A conditioning time of 

48 hours was used to ensure that test materials were equilibrated to the elevated T and RH 

conditions used in testing.
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The small chamber tests shown in Table 1 were conducted using three identical small chambers, 

so that the three tests conducted on each test day were performed simultaneously. Test 

specimens for small chamber testing were cut from large HWPW panels as described in Section 

3.1.1. All nine specimens to be tested on a single day (e.g., the NAF-acrylic specimens on Test 

Day 1 in Table 1) were conditioned together in a single conditioning chamber at the planned test 

conditions of T and RH, and upon completion of conditioning, identical sets of three test 

specimens were placed into each of the three small test chambers. The HWPW specimens

remained in the small test chambers until a steady state HCHO concentration was reached, i.e., 

until approximately 2.5 hours after the start of the small chamber test.

3.3.3 Chromotropic Acid Analysis

The TPC used the chromotropic acid method to quantify HCHO as specified in the ASTM 

E1333 and D6007 test methods, but the calibration curve was extended to lower concentrations 

to assure accurate determination of HCHO emission from the panels. Specifically, standards 

were prepared with smaller amounts of HCHO Standard Solution B than the minimum 0.1 

milliliter (mL) volume stated in the E1333 and D6007 methods.3,4 (Standard Solution B contains 

10 micrograms per milliliter [μg/mL] HCHO, as specified in the ASTM methods.) The 

calibration results for the chromotropic acid method are summarized in Section 4 of this report.
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Chapter 4

Quality Assurance/Quality Control

This chapter summarizes the Quality Assurance/Quality Control efforts and resulting data quality

in this study. The following sections describe the quality of data relevant to the HCHO emission 

results shown in Section 6 of this report.

4.1 Chamber Test Conditions

The T and RH were controlled in each of the chamber tests to achieve the test conditions shown 

in Table 1, with the goal of maintaining chamber T and RH within ± 1 °C and ± 4 %RH,

respectively, of the nominal conditions as stated in the ASTM E1333 and D6007 methods.

3,4

 To 

this end, the chamber T and RH were measured at 1-minute or 5-minute intervals over the entire 

duration of each chamber test. The mean chamber T and mean chamber RH met the respective 

± 1 °C and ± 4 %RH goals in all the large and small chamber tests. Moreover, during each

chamber test, the test conditions were closely controlled as demonstrated by the fact that the 

standard deviation of the individual recorded T values was 0.2 °C or less in 39 of the 54 small 

chamber tests, and never exceeded 0.5 °C. Similarly, the standard deviation of the individual 

recorded RH values met the ± 4 %RH target in 51 of the 54 small chamber tests, with the only

exceptions occurring at elevated RH conditions. Even when controlling at elevated RH 

conditions, the standard deviation of the individual RH values never exceeded 5.3 %RH. In all 

cases the actual mean values of T and RH, rather than the nominal values, were used in the 

statistical analysis of T and RH effects on HCHO emissions.

Inspection of the individual T and RH values recorded in each test similarly showed close 

control of test conditions. All individual T and RH readings were within the target tolerances 

noted above at all times for the large chamber test conducted at 25 °C/50 %RH, and for all but 

one five minute reading (in which the T was just slightly below the target range) for the large 

chamber test conducted at 30 °C/85 %RH. Of the 3,257 total individual T readings and 3,257 

total individual RH readings recorded during the 54 small chamber tests, only 115 of the T 

readings differed by more than 1 °C from the nominal test T, and only 251 of the RH readings 

differed by more than 4 %RH from the nominal test RH. The individual T or RH readings that 

exceeded the target tolerances occurred primarily at the most elevated test conditions, or at the 

beginning of a chamber test when the chamber atmosphere had not yet fully recovered from the 

perturbation caused by opening the chamber to insert the test specimens. 

4.2 Chromotropic Acid Calibration

As is standard practice for the TPC, a single chromotropic acid calibration curve relating 

absorbance to sample HCHO content was prepared at the beginning of this study in August 2012, 

and was applied to all test data. The calibration curve included a method blank and eight 

calibration points based on HCHO amounts ranging from 0.019 to 0.372 micrograms (μg) in the 

calibration standards. The best fit linear regression calibration curve had the form (micrograms 

HCHO) = 17.548 × (absorbance) - 0.0028 μg, with a coefficient of determination (r2) of 0.9912. 

The slope of this calibration curve was within approximately 10 % of previous calibrations 
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performed by the TPC for projects between March and July 2012, indicating that the response of 

the laboratory spectrophotometer and the preparation of the calibration standards were consistent 

over time. 

Fresh sodium bisulfite solution was prepared at least once per week, and the chromotropic acid 

reagent solution was prepared fresh on each day of testing. The absorbance of the sodium 

bisulfite + chromotropic acid reagent (or method blank) was measured on each test day as a 

quality control check. The difference between the absorbance readings of the method blanks and 

that of distilled water was always less than 0.006 absorbance units (equivalent to less than 0.014 

ppm HCHO in the gas phase).

4.3 Chamber HCHO Background

Care was taken to maintain low chamber background levels of HCHO during testing, because of 

the relatively low emissions expected from the HWPW panels being tested. The chamber 

background HCHO concentration was measured using the same chromotropic acid sampling and 

analysis procedures used to determine product HCHO emissions, by sampling of the chamber 

before the products were introduced into the chamber. 

In the two large chamber tests conducted with the ULEF-UF HWPW for comparison to the 

corresponding small chamber results (Sections 3.1.1 and 6.1) the large chamber background 

HCHO was measured to be less than 0.010 ppm. In small chamber tests conducted to assess T 

and RH effects on emissions, the mean (± standard deviation) of the small chamber background 

HCHO values was 0.020 (± 0.009) ppm, based on 22 measurements. A considerable portion of 

the variability in the small chamber background resulted from two small chamber tests in which 

the background exceeded 0.03 ppm. Excluding those two tests, the chamber HCHO background 

averaged 0.017 (± 0.005) ppm, based on 20 measurements, with a maximum value of 0.026 ppm

and a minimum value of 0.009 ppm. 
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Chapter 5

Statistical Methods

As noted in Section 3.1, the results of this study were used to (1) determine whether HCHO

emissions were statistically significantly different under different T and RH conditions, (2) 

determine whether HCHO emissions were statistically significantly different between HWPW 

made with different resin types, and (3) calculate the measurement variability inherent to the

small chamber testing. This chapter summarizes the data analysis used to meet these objectives.

5.1 Large/Small Chamber Test Comparison

Two one-sample comparison tests were performed using HWPW with ULEF-UF resin, one at 

standard T/RH conditions (T = 25 °C, RH = 50 %), and one at elevated T/RH conditions (T = 30

°C, RH = 85 %). The data from these tests are reported in Section 6.1, but due to the small size 

of the data set no formal statistical analysis of these data was conducted.

5.2 Small Chamber Emission Tests

A regression model with interactions was used to model the dependence of HCHO emissions 

from HWPW on T, RH, and resin type. The response variable was HCHO emissions. 

Temperature and RH were continuous predictors in the model. Resin type was a qualitative 

variable with three classes (NAF-acrylic, ULEF-PF, and ULEF-UF). The model included an 

interaction between resin type and T and between resin type and RH. The interaction terms in 

the model allowed for testing whether the response to T and RH differed by resin type and, if so, 

whether the effects of T and RH were statistically significant for each resin type.

Details on the statistical models, hypothesis tests, and limitations to the statistical methods can be 

found in the Appendix.
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Chapter 6

Test Results

 

6.1 Large/Small Chamber Comparison

Table 2 shows the HCHO emission results obtained by testing with the ULEF-UF HWPW in the 

large (E1333) and small (D6007) chambers. For each of the two test conditions used in this 

comparison, Table 2 shows the nominal and actual test conditions of T and RH, the individual 

and mean HCHO results (and standard deviations (SDs)) from the duplicate samples in the large 

chamber, and the individual and mean HCHO results (and SDs) from the triplicate samples in 

each of the three small chambers.

Table 2. Results of Large/Small Chamber Comparison with ULEF-UF HWPW

Nominal Test 

Conditions

(°C/ %RH) Chamber

Actual Test 

Conditions

(°C/ %RH)

Individual HCHO

Sample Resultsa

(ppm)

Mean HCHO 

Sample Results

(ppm)b

25 / 50 

Large 25.6 / 51.1 0.051, 0.051 0.051 (± 0.0)

Smallc

25.2 / 49.9

25.4 / 49.8

25.4 / 50.0

0.049, 0.044, 0.054

0.042, 0.044, 0.052

0.052, 0.044, 0.042

0.049 (±0.005)

0.046 (± 0.005)

0.046 (± 0.005)

30 / 85 

Large 29.3 / 85.1 0.084, 0.092 0.088 (± 0.006)

Smallc

30.2 / 84.4

30.2 / 84.7

30.4 / 84.4

0.111, 0.123, 0.111

0.108, 0.108, 0.116

0.136, 0.133, 0.133

0.115 (± 0.007)

0.111 (± 0.005)

0.134 (± 0.002)

a: Results shown for duplicate samples in large chamber and for triplicate samples in each small chamber. Results 

are not corrected to standard conditions.

b: Average (± standard deviation)

c: Results are from three test chambers used simultaneously. 

Table 2 shows that the large and small chamber test results agreed closely in testing at the 

standard conditions of 25 °C and 50 %RH. This observation is consistent with the fact noted in 

Section 3.1.1 that the TPC laboratory successfully conducted annual CARB equivalency testing

shortly before the start of this study. Note that the test results shown in Table 2 have not been 

adjusted to account for small differences between the actual and standard test conditions. If the 

large chamber result of 0.051 ppm obtained at 25.6 °C and 51.1 %RH (Table 2) were adjusted to 

standard conditions by means of the Berge equations cited in the ASTM test methods3,4 the large 

chamber result would be 0.047 ppm. This result is consistent with the CARB approval of the UF 

HWPW as a ULEF product.

Table 2 also shows that the small chamber results at 30 °C and 85 %RH ranged from about 25 to 

50 % higher than the large chamber result at those test conditions. The reason for this difference 

is unclear. However, both the large and small chamber tests showed HCHO emissions that

exceeded those at the standard conditions of 25 °C and 50 %RH. 
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6.2 Small Chamber Emission Tests

Table 3 summarizes the actual test conditions and HCHO emission results from the 54 small 

chamber tests conducted on the HWPW panels made with different resins. Shown in this table is 

the resin type, the average T and RH, and the HCHO emission value in ppm for each small 

chamber test, and the mean and SD of the three small chamber results in each triplicate set. 

Table 3 lists the tests in the order conducted (i.e., in the same order as in Table 1). The 

consistency of the triplicate results at each test condition is illustrated by the SD values in Table 

3, which are ≤ 0.006 ppm in most tests, with values of 0.010 to 0.012 ppm in tests with the 

ULEF-UF panels at elevated T and/or RH.

Table 3. Test Conditions and HCHO Results from Small Chamber Testsa

Resin Type

T 

(°C)

RH 

(%)

HCHO 

(ppm)

Mean

(± SD) Resin Type

T 

(°C)

RH 

(%)

HCHO 

(ppm)

Mean

(± SD)

NAF-acrylic 25.4 51.4 0.027 0.024

(± 0.003)

NAF-acrylic 25.2 70.7 0.019 0.025

(± 0.006)

NAF-acrylic 25.7 52.8 0.022 NAF-acrylic 25.4 69.7 0.026

NAF-acrylic 26.0 50.0 0.023 NAF-acrylic 25.5 70.0 0.030

ULEF-PF 25.4 53.8 0.034 0.037

(± 0.003)

ULEF-PF 25.3 84.9 0.023 0.025

(± 0.004)

ULEF-PF 25.4 51.7 0.039 ULEF-PF 25.4 84.5 0.022

ULEF-PF 25.5 52.3 0.037 ULEF-PF 25.4 85.0 0.029

ULEF-PF 30.2 66.5 0.056 0.054

(± 0.005)

ULEF-PF 30.2 83.8 0.023 0.025

(± 0.003)

ULEF-PF 30.2 69.0 0.058 ULEF-PF 30.3 83.7 0.028

ULEF-PF 30.3 69.8 0.048 ULEF-PF 30.3 84.5 0.024

NAF-acrylic 30.2 69.7 0.034 0.031

(± 0.004)

ULEF-UF 25.2 49.9 0.049 0.047

(± 0.002)

NAF-acrylic 30.3 70.1 0.026 ULEF-UF 25.4 49.8 0.046

NAF-acrylic 30.4 69.2 0.033 ULEF-UF 25.4 50.0 0.046

ULEF-PF 30.2 49.6 0.042 0.046

(± 0.003)

ULEF-UF 30.2 70.0 0.110 0.108

(± 0.005)

ULEF-PF 30.2 50.1 0.048 ULEF-UF 30.2 69.6 0.111

ULEF-PF 30.3 50.0 0.048 ULEF-UF 30.4 69.2 0.102

NAF-acrylic 29.8 49.5 0.041 0.036

(± 0.006)

ULEF-UF 30.2 84.4 0.115 0.120

(± 0.012)

NAF-acrylic 30.1 49.5 0.038 ULEF-UF 30.2 84.7 0.111

NAF-acrylic 30.3 49.9 0.029 ULEF-UF 30.4 84.4 0.134

NAF-acrylic 30.2 83.0 0.032 0.032

(± 0.0)

ULEF-UF 30.2 49.9 0.099 0.095

(± 0.010) NAF-acrylic 30.2 84.6 0.032 ULEF-UF 30.2 50.0 0.102

NAF-acrylic 30.4 84.7 0.032 ULEF-UF 30.3 49.8 0.083

NAF-acrylic 25.2 84.9 0.013 0.015

(± 0.004)

ULEF-UF 25.3 84.8 0.081 0.093

(± 0.012)

NAF-acrylic 25.5 85.0 0.019 ULEF-UF 25.5 84.6 0.104

NAF-acrylic 25.4 84.9 0.012 ULEF-UF 25.4 85.3 0.095

ULEF-PF 25.3 70.2 0.023 0.020

(± 0.004)

ULEF-UF 25.3 70.2 0.067 0.066

(± 0.011)

ULEF-PF 25.4 70.0 0.016 ULEF-UF 25.4 69.8 0.076

ULEF-PF 25.4 67.7 0.020 ULEF-UF 25.4 69.2 0.054

a Air exchange rate in all small chamber tests = 0.5/hour

Figure 1 displays the HCHO emission results by RH at both 25 °C and 30 °C for all three types 

of HWPW (i.e., HWPW made with three different resins) in this study. This figure incorporates 

the test results listed in Table 3, and illustrates clear trends in the emission results over the range 

of T and RH used in testing. Figure 1 shows linear relationships with respect to T and RH for 

the panels made with ULEF-UF (green symbols and traces) and NAF-acrylic (blue symbols and 

traces) resin types. For the ULEF-UF panel, the HCHO emissions at the highest T and RH 

conditions (30 °C/85 %RH) are approximately 0.075 ppm higher than the emissions at the 
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standard conditions (25 °C/50 %RH). A more complex relationship with respect to T and RH is 

observed for the ULEF-PF panel type (red symbols and traces in Figure 1). For this panel type 

HCHO emissions are similar for both T levels at 50 %RH and at 85 %RH, but they differ 

considerably at 70 %RH. It is not clear what is causing this type of relationship. 

 TSCA Title VI requires no test result higher than 0.05 ppm (under standard T and 

 RH conditions) for HWPW made with ULEF resins to qualify for a TPC exemption.

Figure 1. HCHO emissions vs. RH for T=25 °C and T=30 °C.

6.2.1 Effect of Resin Type on HCHO Emissions

One objective of the study was to determine whether the panels made with the three resin types 

responded differently to elevated T and RH. To address this question, we conducted three 

separate comparisons: ULEF-UF vs. NAF-acrylic, ULEF-UF vs. ULEF-PF, and NAF-acrylic vs. 

ULEF-PF. For each pair of resin types, we conducted three hypothesis tests to determine 

whether there was a difference in the intercept, a difference in the coefficients corresponding to 

T, and a difference in the coefficients corresponding to RH. In each hypothesis test, the null 

hypothesis of no difference (e.g., equal intercepts and equal slopes) was tested against the 

50 55 60 65 70 75 80 85

0.02

0.04

0.06

0.08

0.10

0.12

0.14

RH (%)

H

C

H

O

E

mission (ppm)

NAF-acrylic 25C

ULEF-PF 25C

ULEF-UF 25C

NAF-acrylic 30C

ULEF-PF 30C

ULEF-UF 30C
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alternative of a difference (e.g., either the intercept differed or one of the slopes differed). If at 

least one of the hypothesis tests for a pair of resins found a difference, we concluded that the 

responses were not identical for that pair of resins.

For the ULEF-UF vs. NAF-acrylic comparison, the intercept, the T coefficient, and the RH 

coefficient were all statistically different between the two resin types (all three p-values <0.001), 

indicating that the two panels used in this experiment behaved differently under the testing 

condtions. Compared to the NAF-acrylic panels, the ULEF-UF panels emitted a higher level of 

HCHO overall (higher intercept) and responded differently to changes in T and RH (different 

slope parameters). This is evident from Figure 1 in that all ULEF-UF results are greater than the 

corresponding NAF-acrylic results, and the slope of the fitted regression line for the ULEF-UF 

emission results was higher than that for the NAF-acrylic emission results.

For the ULEF-UF vs. ULEF-PF comparison, the intercept, the T coefficient, and the RH 

coefficient were all statistically different between the two resin types (all three p-values <0.001), 

indicating that the two panels behaved differently under the testing condtions. Compared to the 

ULEF-PF panels, the ULEF-UF panels emitted a higher level of HCHO overall (higher intercept) 

and responded differently to changes in T and RH (different slope parameters). This is evident

in Figure 1 in that all ULEF-UF panel results are greater than the corresponding ULEF-PF panel

results, and the slope of the fitted regression line for the ULEF-UF emission results was higher 

than that for the ULEF-PF emission results.

For the NAF-acrylic vs. ULEF-PF panel comparison, the intercept, the T coefficient, and the RH 

coefficient were not statistically different between the two resin types (all three p-values > 0.14), 

indicating that the two panels behaved similarly under the testing conditions. This is evident in 

Figure 1 in that ULEF-PF panel results are mixed among NAF-acrylic panel results and that the 

fitted regression lines appear similar.

The estimated coefficients of the T and RH effects and the standard errors of those coefficients 

determined in the statistical analysis are summarized in Table 4, and the results are described in 

Sections 6.2.2 and 6.2.3. Table 4 shows, for each panel type, the estimated coefficients for T and 

RH, the respective standard errors, and the p-value indicating the strength of the indicated 

statistical relationship. 
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Table 4. Estimates and Standard Errors from Regression Model

Effect Panel Type

Estimated 

Coefficient

Standard 

Error p-valuec

T

ULEF-UF 0.0080a0.00078a< 0.0001

ULEF-PF 0.0029a0.00078

a

0.0006

NAF-acrylic 0.0024a0.00080a0.00434

RH

ULEF-UF 0.0010b0.00013b< 0.0001

ULEF-PF -0.0005

b

0.00014

b

0.0010

NAF-acrylic -0.0002

b

0.00014

b

0.1545

a: Units of temperature coefficients and standard errors are ppm HCHO/°C.

b: Units of relative humidity coefficients and standard errors are ppm HCHO/%RH.

c: Statistically significant effects have a p-value below 0.0033, a threshold that ensures an experimentwise 

error rate of less than α = 0.05.

Table 5 summarizes the cumulative effects of T and RH found in this study. For all three panel 

types, Table 5 shows the statistically determined coefficients that quantify the change in HCHO 

emission for a unit change in T or RH over the range of conditions tested. Table 5 also shows 

the resulting changes in HCHO emission (in ppm) for each resin type that occurred over the 

range of T and RH used in testing. The changes in HCHO emission due to T and RH are shown 

separately, and the combined change resulting from both T and RH together is also shown. 

Table 5 shows that HCHO emission from ULEF-UF and ULEF-PF panel types increased with 

increasing T over the range of 25 to 30 °C used in testing. However, the effect of T for the 

ULEF-UF panels was approximately three times as large as for the ULEF-PF panels, and 

amounted to an increase in HCHO emissions of approximately 0.008 ppm per °C increase in T 

over the indicated range. Table 5 also shows that HCHO emissions from the ULEF-UF panels 

increased with increasing RH over the range of 50 to 85 %RH used in testing, at a rate of 

approximately 0.001 ppm per 1 %RH increase over that range. 

Table 5. Summary of Temperature and Relative Humidity Effects on Formaldehyde 

Emissions from Three Types of Hardwood Plywood

Resin Type

Coefficient of 

T or RH Effect Separate Effect on Emissions Combined 

Effect on 

Emissionsc

(ppm HCHO)

T 

(ppm 

HCHO/°C)

RH 

(ppm 

HCHO/%RH)

T

a

(ppm HCHO)

RHb

(ppm HCHO)

ULEF-UF 0.0080 0.0010 0.0400 0.0359 0.0759

ULEF-PF 0.0029 -0.0005 0.0148 -0.0171 -0.0023

NAF-acrylicd0.0024 -0.0002 0.0121 -0.0069 0.0052

a: Change in formaldehyde emission (in ppm) due to T between 25 and 30 °C.

b: Change in formaldehyde emission (in ppm) due to RH between 50 and 85 %RH. 

c: Total change in formaldehyde emission due to T and RH between 25 °C/50 %RH and 30 °C/85 %RH.

d: Neither T nor RH effects were statistically significant for NAF-acrylic. 
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The combined effect of T and RH increased the HCHO emission of the ULEF-UF panels by

approximately 0.076 ppm between the standard conditions of 25 °C/50 %RH and the most 

elevated test conditions of 30 °C/85 %RH, with the T and RH effects contributing roughly 

equally to this increase. In contrast, the HCHO emissions from the ULEF-PF panels decreased 

slightly with increasing RH, as indicated by the negative RH coefficient in Table 5. The 

combined effect of T and RH on formaldehyde emission of the ULEF-PF panels was close to 

zero, i.e., a calculated decrease in emission of approximately 0.002 ppm between the standard 

conditions of 25 °C/50 %RH and the most elevated test conditions of 30 °C/85 %RH. The cause 

of the apparent reduction in formaldehyde emission with increasing RH for the ULEF-PF panels 

is not known, and was not investigated in this study. Neither the T nor RH effect was 

statistically significant for the NAF-acrylic HWPW panels, and the combined effect of T and RH 

was close to zero, i.e. a calculated increase in emission of approximately 0.005 ppm between the 

standard conditions of 25 °C/50 %RH and the most elevated test conditions of 30 °C/85 %RH.

6.2.2 Effect of Temperature on HCHO Emissions

The effect of T on HCHO emissions for the ULEF-UF panels used in this study was statistically 

significant (p-value <0.0001), and the value of the T coefficient was greater than zero (≈ 0.008). 

This T effect can be seen in Figure 1 in that the 30 °C ULEF-UF emission results are greater 

than the corresponding 25 °C ULEF-UF emission results. Therefore, it was concluded that 

HCHO emissions from the ULEF-UF panels used in this study increase with T, and that (based 

on the coefficient in Table 4) every 1 °C increase in T between 25 °C and 30 °C results in an 

increase in HCHO emission of approximately 0.008 ppm.

The effect of T on HCHO emissions for the ULEF-PF panels used in this study was statistically 

significant (p-value 0.0006) and the value of the T coefficient was greater than zero (≈ 0.003). 

Therefore, it was concluded that HCHO emissions from the ULEF-PF panels used in this study

increase with T at approximately 0.003 ppm per °C increase in T between 25 °C and 30 °C 

(based on the coefficient in Table 4). This T effect can be seen in Figure 1 in that most of the 30 

°C ULEF-PF emission results are greater than those of the corresponding 25 °C ULEF-PF

samples.

The effect of T on HCHO emissions for the NAF-acrylic panels used in this study was not 

statistically significant (p-value 0.00434). Although most of the emission results from the 30 °C

NAF-acrylic panels are greater than the corresponding 25 °C NAF-acrylic emission results in 

Figure 1, these T differences are not statistically significant with respect to the panels used in this

study.

6.2.3 Effect of Relative Humidity on HCHO Emissions

The effect of RH on HCHO emissions for the ULEF-UF panels used in this study was 

statistically significant (p-value <0.0001) and the value of the RH coefficient was greater than 

zero (≈ 0.001). Therefore, it was concluded that HCHO emissions increase with increasing RH

for the ULEF-UF panels used in this study at approximately 0.001 ppm for each 1 %RH increase 

between 50 and 85 %RH. This RH effect is evident in Figure 1 in that HCHO emissions 

increase as RH increases for the ULEF-UF product.
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The effect of RH on HCHO emissions for the ULEF-PF panels used in this study was 

statistically significant (p-value =0.0010) and the value of the RH coefficient was negative (-

0.0005). Therefore, it was concluded that HCHO emissions decrease with increasing RH for the 

ULEF-PF panels used in this study, at approximately 0.0005 ppm for each 1 %RH increase 

between 50 and 85 %RH. As illustrated in Figure 1, the emission results from the ULEF-PF

panels at 30 °C and 70 %RH are greater than those at both 50 and 85 RH. It is not clear whether 

those results represent the T/RH behavior of the ULEF-PF material or are due to some variation 

in the testing.

The effect of RH on HCHO emissions for the NAF-acrylic panels used in this study was not 

statistically significant (p-value = 0.1545). 

6.2.4 Characterization of Measurement Variability Inherent to Small Chamber Testing

The variance of the model residuals, calculated using the equation presented in the Appendix, 

was 6.4958 × 10-5. The square root of this estimator is 0.00806 ppm, which is slightly lower 

than the variability estimate noted in the small chamber ASTM method documentation4(i.e., 

within-laboratory precision of approximately 0.01 to 0.02 ppm for small chamber tests). It is 

therefore concluded that the within-laboratory variability in the small chamber tests conducted in 

this study is well within the variability expected, after accounting for the effects of the variations 

in T, RH, and resin type.
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Chapter 7

Summary and Conclusions

Hardwood plywood panels made with three different types of ULEF resins were tested to 

determine the effect on HCHO emissions of T and RH conditions other than the standard test 

conditions of 25 °C and 50 %RH . The panels tested included HWPW made with NAF-acrylic, 

ULEF-PF, and ULEF-UF resins. Testing was conducted using the small chamber method

(ASTM D6007) under test conditions of 50, 70, and 85 %RH at each of two temperatures (25 

and 30 °C). Triplicate small chamber tests were performed on each HWPW-resin panel type at 

each of the six T/RH conditions. The resulting HCHO emission results were analyzed with 

statistical models to assess the differences in emission behavior from HWPW panels made with 

the three resin types, the effects of T and RH on emissions, and the variability of the small 

chamber test procedure.

Emission Behavior from HWPW Panels made with the Three Resin Types

 The study results show that the ULEF-UF panels differed significantly in emission 

behavior from both the NAF-acrylic and ULEF-PF panels. 

 HCHO emissions from HWPW panels made with ULEF-UF resin were found to increase 

with T and RH. The effects of both T and RH on emissions from ULEF-UF panels were

large in relation to the TSCA Title VI limit of 0.05 ppm and statistically significant with 

respect to the panels used in the study. 

 HCHO emissions from HWPW panels made with ULEF-PF resin increased with T but 

decreased with RH. The effects of both T and RH were small relative to the TSCA Title 

VI 0.05 ppm limit, but statistically significant with respect to the panels used in the study. 

 The relationships between HCHO emissions and T and RH for HWPW panels made with 

NAF-acrylic resin were not statistically significant with respect to the panels used in the 

study. 

Quantified Effects of T and RH on HCHO Emissions 

 Statistical analyses were performed to determine coefficients that quantify the change in 

HCHO emissions for a unit change in T or RH over the range of conditions tested. 

 For HWPW panels made with ULEF-UF resin, HCHO emissions increased by

approximately 0.008 ppm per °C increase in T over the range of 25 to 30 °C, for a fixed 

RH. HCHO emissions increased by approximately 0.001 ppm for each 1 %RH increase 

in RH over the range of 50 to 85 %RH, for a fixed T. The combined effect of T and RH 

was to increase HCHO emissions from the ULEF-UF panels used in this study by

approximately 0.0759 ppm between standard test conditions (25 °C/50 %RH) and the 

most elevated conditions tested (30 °C/85 %RH). The effect of T on emissions from 

ULEF-UF panels evaluated for this study was approximately 3 times as great as for 

ULEF-PF or NAF-acrylic over the temperature range tested. 

 For HWPW panels made with ULEF-PF resin, HCHO emissions increased by

approximately 0.0029 ppm per °C increase in T over the range of 25 to 30 °C, for a fixed 

RH. HCHO emissions decreased by approximately 0.0005 ppm for each 1 % increase in 

RH over the range of 50 to 85 %RH, for a fixed T. The combined effect of T and RH was 

to decrease HCHO emissions from the ULEF-PF panels used in this study by
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approximately 0.0023 ppm between standard test conditions (25 °C/50 %RH) and the 

most elevated conditions tested (30 °C/85 %RH). 

 For HWPW panels made with NAF-acrylic resin, HCHO emissions increased by about 

0.0052 ppm between standard test conditions (25 °C/50 %RH) and the most elevated 

conditions tested (30 °C/85 %RH), although neither the T nor the RH effect on emissions 

was statistically significant with respect to the panels used in the experiment.

Table 6 summarizes the results of this study. For each panel type used in the study, Table 6 

reports the HCHO emission at the standard testing conditions (25 °C/50 %RH) and at the highest 

T and RH conditions (30 °C/85 %RH), based on the statistical analysis of all test results for that 

panel type. Table 6 also shows the change in HCHO emissions between the standard testing 

conditions and the highest conditions. 

Table 6. Comparison of HCHO Emissions of Three Hardwood Plywood Panel Types at 

Lowest and Highest Temperature and Relative Humidity Conditions 

HWPW 

Panel Type

HCHO Emission

at 25 °C/50 %RH 

(ppm)

HCHO Emission 

at 30 °C/85 %RH

(ppm)

Change

(ppm)

ULEF-UF 0.0471 0.1230 0.0759

ULEF-PF 0.0356 0.0333 -0.0023

NAF-acrylic 0.0238 0.0290 0.0052

Note: TSCA Title VI requires no test result higher than 0.05 ppm (under standard T and RH conditions) for HWPW made 

with ULEF resins to qualify for a TPC exemption.

The observed emission behavior of the three different types of HWPW used in this study is 

consistent with the nature of the resins used in their manufacture. The minimal emission rates 

and absence of T and RH effects with the ULEF-NAF-acrylic panels reflect the absence of 

HCHO in the NAF resin. The ULEF-UF and ULEF-PF panels are both made with resins 

containing HCHO. However, the differences in their emission rates and T and RH effects are 

consistent with the greater chemical stability of the PF resin relative to the UF resin against 

degradation by moisture. This stability makes PF resin wood products particularly suitable for 

external applications where exposure to variable environmental conditions may occur.11,12

Variability of the Small Chamber Test Procedure

 Statistical analysis of the variability of the small chamber tests produced a variance 

estimate, the square root of which is 0.00806 ppm. 

 This uncertainty value is slightly lower than the within-laboratory precision of stated in 

the ASTM small chamber method (approximately 0.01 to 0.02 ppm).

4

 

 This result indicates that the within-laboratory test variability achieved in this study is 

well within the variability expected, after accounting for the effects of the variations in T, 

RH, and resin type. 
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Chapter 8

References

1. Airborne Toxic Control Measure to Reduce Formaldehyde Emissions from Composite 

Wood Products, Section 93120. California Air Resources Board, 2007. Available at 

http://www.arb.ca.gov/regact/2007/compwood07/fro-final.pdf.

2. Formaldehyde Standards for Composite Wood Products Act, 111th Congressional Record 

S4891-92 (daily ed. June 14, 2010) and H4701-05 (daily ed. June 23, 2010), available at 

http://www.gpoaccess.gov/crecord/digest2010/d14JN101.html.

3. Standard Test Method for Determining Formaldehyde Concentrations in Air and 

Emissions Rates from Wood Products Using a Large Chamber, ASTM E1333-96 (2002), 

American Society for Testing and Materials, 2002. Available for purchase at 

http://enterprise.astm.org/filtrexx40.cgi?HISTORICAL/E1333-96R02.htm

4. Standard Test Method for Determining Formaldehyde Concentrations in Air from Wood 

Products Using a Small-Scale Chamber, ASTM D6007-02 (2008), American Society for 

Testing and Materials, 2008. Available for purchase at http://dx.doi.org/10.1520/D6007-

02R08.

5. Frihart, C. R., Wescott, J. M., Birkeland, M. J., and Gonner, K. M., Formaldehyde 

Emissions from ULEF- and NAF-Bonded Commercial Hardwood Plywood as 

Influenced by Temperature and Relative Humidity. Published in the Proceedings of the 

International Convention of the Society of Wood Science and Technology and United 

Nations Economic Commission for Europe – Timber Committee. October 11-14, 2010, 

Geneva, Switzerland.

6. Riedlinger, D., Martin, P., and Holloway, T., Particleboard Formaldehyde Emissions and 

Decay under Elevated Temperature and Humidity Conditions, study conducted for 

Arclin, Inc., March 28, 2012.

7. Huber, C.W., Anderson, W.H., Vieira, J. W., and Liles, W.T., The Dynamic 

Microchamber Computer Integrated Formaldehyde Test System: User Manual, revised 

version, March 2007; available at www.gp-dmc.com.

8. Myers, G.E., The effects of temperature and humidity on formaldehyde emission from 

UF-bonded boards: a literature critique, Forest Prod. J., 35(9):20-31, 1985.

9. Dean, A. and Voss, D. (1999) Design and Analysis of Experiments. New York: Springer.

10. Hsu, J. C. (1996) Multiple Comparisons: Theory and Methods. Boca Raton: Chapman & 

Hall/CRC.
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11. The Encyclopedia of Wood, ISBN-13: 978-1-60239-057-7, U.S. Department of 

Agriculture, Washington, D.C., 1999.

12. Gardziella, A., Pilato, L.A., and Knop, A., Phenolic Resins: Chemistry, Applications, 

Standardization, Safety, and Ecology, 2nd Edition, ISBN 3-540-65517-4, SpringerVerlag, Berlin, 1999. 
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Appendix A

Statistical Methodology

This appendix provides details on the statistical methodology used to analyze the data from the 

small chamber emission tests.

A.1 Overview

A regression model with interactions was used to model the dependence of HCHO emissions 

from HWPW on T, RH, and resin type. Formaldehyde emissions, T, and RH are continuous 

variables in the model. Resin type is a qualitative variable with three classes (NAF-acrylic, 

ULEF-PF, and ULEF-UF); therefore, two indicator variables were used in the model. 

The regression model with interactions assumes that after accounting for differences in 

conditioning and resin type, all measurements are independent of each other. This is a 

reasonable assumption because all small chamber testing was done on samples from three 

HWPW panels of each resin type. The experimental units can be viewed as independent samples 

where the “population” is the exact set of panels used in the experiment (three panels for each of 

three resin types). Thus, the experiment satisfies the assumptions underlying the regression 

model. All estimates of variability and tests of statistical significance apply to the variability due 

to sampling from the panels in the experiment and using different chambers for testing. These 

results cannot be extended to the population of panels in current or future use that were not 

sampled as part of the experiment. We also cannot assess panel-to-panel variability in the panel 

lots because no single HCHO measurement can be attributed to one specific panel.

Before the data were fit to the model, HCHO emissions were plotted against T and RH to 

determine whether or not a linear relationship was reasonable between the variables. The 

assumption of a linear relationship between HCHO emissions and T and RH was found to be 

reasonable for ULEF-UF and NAF-acrylic panels. The relationship between HCHO emissions 

and T and RH for the ULEF-PF panels was more complex, but a linear relationship was assumed 

because the source of the complex pattern was not clear, and there were too few experimental 

conditions to allow consideration of a more complex model.

Statistical tests, described below, were conducted to explore the relationships between HCHO 

emissions and resin type, T, and RH. The analysis consists of 15 hypothesis tests on the various 

model parameters. Consequently, the threshold significance level was adjusted for each test such 

that the overall experiment-wise significance level was α = 0.05. The threshold statistical 

significance level was corrected using the Bonferroni method found in many statistical texts.9,10 

To apply this correction, each hypothesis was tested at a threshold significance level of 0.0033, 

which is equal to 0.05/15. This threshold significance value gives an experiment-wise error rate 

of α = 0.05 adjusted for multiple comparisons. 

A.2 Statistical Models

The formulation of the model is as follows. Let
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 = HCHO emissions from HWPW from	measurement	

 = T at measurement 

 = RH at measurement 

 = 1 if resin type at measurement  is NAF acrylic; 0 otherwise, and

 = 1 if resin type at measurement  is ULEF PF; 0 otherwise.

The regression model with interactions is then:

 =  + +  +  +  +  +  +  +  + ε (1)

Where it is assumed that the εiterms are independent and identically distributed N(0, σ



) for 

i = 1, ... , n.

The response function for model (1) is then:

[] =  +  +  +  +  +  +  +  + 

The response function can be simplified according to resin type. For example, the response 

function for resin type ULEF-UF, for which Z1=0 and Z2=0, is as follows:

[] =  +  + 

For resin type NAF-acrylic, Z1=1 and Z2=0, and the response function is:

[] =  +  +  +  +  +  = ( + 

) + ( + ) + ( + )

Finally, for resin type ULEF-PF, Z1=0 and Z2=1, the response function is:

[] =  +  +  +  +  +  = ( + 

) + ( + ) + ( + )

Thus, interaction regression model (1) implies that each resin type has its own regression line, 

with different intercepts and slopes for the different resin types. 

One benefit to using the interaction regression model instead of separately fitting three 

regression models, one for each resin type, is that the former model uses 54 observations (see 

Sect. 3.1.2) as opposed to only 18 observations for each of the three individual models by resin 

type. Since the interaction regression model has many more observations used in its fit 

compared the other models, it provides a better estimate of the error term (σ



), and therefore 

provides more powerful results. Furthermore, a combined regression model facilitates 

comparing results across resin types, a key question of interest to EPA.

A.3 Hypothesis Tests

In order to investigate whether HCHO emissions were statistically significantly different 

between HWPW made with different resin types, three formal hypothesis tests were performed, 

one for each pair of resin types.
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Testing the equality of the two response functions for ULEF-UF and NAF-acrylic involved the 

alternatives:

:  =  =  = 0

:       

Testing the equality of the two response functions for ULEF-UF and ULEF-PF involved the 

alternatives:

:  =  =  = 0

:       

If the two tests above both failed to reject the null hypothesis that the functions were equivalent 

(i.e., there is no evidence to contradict that  =  =  = 0 and  =  =  = 0), then there 

is no need to test the equality of the two response functions for ULEF-PF and NAF-acrylic, as 

that test would also fail to reject the null hypothesis that the response functions are equivalent. If 

one of the two tests above failed to reject the null hypothesis and the other test rejected the null 

hypothesis (i.e., concluded that the response functions are different), then again there would be 

no need to test the equality of the two response functions for ULEF-PF and NAF-acrylic, as that 

test would also reject the null hypothesis and conclude that the response functions are not 

equivalent. If both tests above reject the null hypothesis and conclude that the response 

functions are not equivalent, then a third test to test the equality of the two response functions for 

ULEF-PF and NAF-acrylic would be conducted using the following alternatives:

:  =   =    = 

:     ≠  

The results of these tests determine the regression line for each resin, and this in turn impacts the

investigation of whether or not formaldehyde emissions are statistically significantly different 

under different T or RH conditions. For example, if all three tests above fail to reject the null 

hypothesis, then this essentially means that there is not enough evidence to conclude a different 

regression line for each resin. In other words, model (1) reduces to

 =  + +  + ε

For this reduced model, testing whether or not HCHO emissions are statistically significantly

different under different T conditions for any resin type involves the alternatives:

:  = 0

:  ≠ 0

Similarly for the reduced model, testing whether or not HCHO emissions are statistically

significantly different under different RH conditions for any resin type involves the alternatives:

:  = 0
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:  ≠ 0

However, if at least one of three response function equivalency tests between two resins rejects 

the null hypothesis, then model (1) may be reduced, but not to the extent just shown. For 

example, if all three response function equivalency tests reject the null hypothesis, meaning that 

each resin type has a unique regression line, then as previously shown, the response function for 

resin type ULEF-UF (Z1=0 and Z2=0) is:

[] =  +  + 

For resin type NAF-acrylic (Z1=1 and Z2=0) the response function is:

[] = ( + 

) + ( + ) + ( + )

And for resin type ULEF-PF (Z1=0 and Z2=1) the response function is:

[] = ( + 

) + ( + ) + ( + )

Thus, model (1) implies that each resin type has its own regression line, with different intercepts 

and slopes for the different resin types, so different hypothesis tests were conducted to determine 

the statistical significance of T and RH for each resin type. Under this “full” model, testing 

whether or not HCHO emissions are statistically significantly different under different T 

conditions for ULEF-UF involves the alternatives:

:  = 0

:  ≠ 0

Similarly under this “full” model, testing whether or not HCHO emissions are statistically 

significantly different under different RH conditions for ULEF-UF involves the alternatives:

:  = 0

:  ≠ 0

Again under this “full” model, testing whether or not HCHO emissions are statistically

significantly different under different T conditions for NAF-acrylic involves the alternatives:

:  +  = 0

:  +  ≠ 0

and testing whether or not HCHO emissions are statistically significantly different under 

different RH conditions for NAF-acrylic involves the alternatives:

:  +  = 0

:  +  ≠ 0
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Finally under the “full” model, testing whether or not HCHO emissions are statistically

significantly different under different T conditions for ULEF-PF involves the alternatives:

:  +  = 0

:  +  ≠ 0

and testing whether or not HCHO emissions are statistically significantly different under 

different RH conditions for ULEF-PF involves the alternatives:

:  +  = 0

:  +  ≠ 0

The tests of whether or not HCHO emissions are statistically significantly different under 

different T and RH conditions have been outlined for the cases where model (1) reduces 

completely to one regression line and where model (1) is not reduced at all (i.e., the “full” 

model). However, depending on the data and the outcomes of the equivalency response function 

tests between two resin types, model (1) ended up being something between these two extremes, 

and statistical tests involving T and RH were modified accordingly. That is, the analysis found 

that ULEF-UF behaved differently from ULEF-PF and NAF-acrylic, but ULEF-PF and NAFacrylic behaved similarly to each other. Based on their similarities, statistical tests could be 

modified to examine the effect of T/RH on the combined ULEF-PF/NAF-acrylic observations.

However, because of the chemical and physical differences between ULEF-PF and NAF-acrylic, 

all statistical tests were conducted assuming 3 separate resin types.

A.4 Characterizing Measurement Variability

To characterize the measurement variability inherent to small chamber testing, the following 

estimator was calculated:



 =

1

45( − 

)







where is observation i and 



is the predicted value for observation i on the appropriate fitted 

regression line. 



is an unbiased estimator for σ



, the variance of model (1). The square root of 

this estimator (S) was compared to the within-laboratory precision estimate noted in the ASTM 

D6007 documentation4of approximately 0.01 to 0.02 ppm.
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Appendix B

Emission Testing of First Batch of Commercial ULEF-UF Panels

B.1 Introduction

The first batch of ULEF-UF panels tested gave unexpectedly high emission testing results and 

therefore were not used in evaluating the effects of temperature and humidity on emissions. This 

appendix describes these panels and the emission testing results.

B.2 Product Description

The first ULEF-UF panels tested were 5-ply veneer core HWPW, 0.5 inch thick and 4 ft by 8 ft 

in size. The panels were manufactured on July 10, 2012, and shipped directly from the 

manufacturer to the testing laboratory, where they were received on July 16 as a stack of 10 

panels wrapped in plastic sheet. The panels were labeled as compliant with the CARB ATCM 

and “93120 TPC Exempt.” The panels were stored, cut to size for chamber testing, and 

equilibrated with T and RH conditions as described in section 3.1.1 of this study report.

B.3 Emission Testing

The HWPW was subjected to HCHO emission tests using both the ASTM large chamber 

(E1333) and small chamber (D6007) methods. The tests were intended to provide a comparison 

of the HCHO emissions when determined under the same T and RH conditions by both the large 

and small chamber methods. Table 1 summarizes the 13 tests conducted on the HWPW panels. 

The tests in Table 1 are listed and numbered in chronological order, and the table shows the test 

date, the chamber size (large or small), the nominal and actual T and RH conditions, the HCHO 

emission in ppm, and notes concerning each test. As described in section 3.1.1, the large 

chamber tests were conducted singly, whereas the small chamber tests were conducted as 

simultaneous triplicate tests.
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Table B.1. Chamber tests conducted on a Commercial Veneer Core Hardwood Plywood 

Test 

Number Date Chamber

Nominal 

T/RH

(°C/%)

Actual T 

/RH

(°C/%)

HCHO 

Emission

(ppm) Notes

1 8/2/12 Large125/50 25.6/49.1 0.080 Invalidated – 48 hour conditioning

2 8/2/12 Small225/50 25.3/50.0 0.117

3 8/2/12 Small 25/50 25.1/50.0 0.110

4 8/2/12 Small 25/50 25.5/50.2 0.110

5 8/8/12 Large 30/85 30.0/85.1 0.220 Invalidated – 48 hour conditioning

6 8/14/12 Small 25/50 25.5/51.0 0.123

7 8/14/12 Small 25/50 25.1/50.1 0.120

8 8/14/12 Small 25/50 25.4/50.9 0.120

9 8/17/12 Small 30/85 30.0/90.2 0.166

10 8/17/12 Small 30/85 30.1/86.9 0.162

11 8/17/12 Small 30/85 30.6/92.2 0.155

12 8/24/12 Large 25/50 26.1/50.5 0.040 Repeat of Test 1 – 7 day

conditioning

13 9/26/12 Large 30/85 30.1/85.1 0.199 Repeat of Test 5 – 7 day

conditioning

1

: ASTM E1333

2

: ASTM D6007

As a comparison of large and small chamber results at the same T and RH conditions, it was 

intended that Test 1 would be compared to Tests 2 to 4, and that Test 5 would be compared to 

Tests 9 to 11. Tests 6 to 8 were small chamber tests conducted as part of the planned T/RH test 

matrix, and are replicates of Tests 2 to 4. However, the HWPW panels were only conditioned for 

48 hours prior to Tests 1 and 5, rather than for 7 days as required in the large chamber method, 

and consequently, those two tests were invalidated and were repeated as Tests 12 and 13, 

respectively.

Table 1 shows that after 7 days of conditioning at the standard T and RH conditions of 25 °C and 

50 %RH (Test 12), the HWPW exhibited a HCHO emission of 0.040 ppm in the large chamber 

test, consistent with its designation as a ULEF product (the ULEF emission standard is 0.05 

ppm). However, in the corresponding small chamber tests (Tests 2 to 4 and 6 to 8) the HWPW 

exhibited HCHO emissions ranging from 0.110 to 0.123 ppm, substantially higher than both the 

large chamber result and the ULEF emission standard. Samples for the small chamber tests were 

conditioned for 48 hours at the test conditions prior to testing.

Table 1 also shows that after 7 days of conditioning at the elevated T and RH conditions of 30 °C 

and 85 %RH (Test 13), the HWPW exhibited a HCHO emission of 0.199 ppm in the large 

chamber test. In the corresponding small chamber tests (Tests 9 to 11) the HWPW exhibited 

HCHO emissions ranging from 0.155 to 0.166 ppm. These results suggested that the HCHO 
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emissions of the ULEF-UF HWPW increased at the elevated T and RH conditions relative to 

those at the standard T and RH conditions. 

Because of the unexpectedly high HCHO emissions of the HWPW in the small chamber tests at 

standard conditions (Tests 2 to 4 and 6 to 8), testing of this batch of panels was discontinued, and

panels from another manufacturer were obtained. The intent of this study was to assess the 

impact of elevated T and RH on HCHO emissions of panels that meet the NAF or ULEF 

definitions. Because these HWPW panels did not meet the ULEF emission standard in the small 

chamber tests at the standard conditions, they were not used for evaluating the impact of elevated 

T and RH on formaldehyde emissions.