EPA/600/A-97/006
OBSERVATIONS ON APPLICATION OF THE FIELD AND
LABORATORY EMISSION CELL (FLEC) FOR LATEX PAINT
EMISSIONS - EFFECT OF RELATIVE HUMIDITY
N. Roache1, E. Howard2, Z. Guo1, and R. Fortmann'
'Acurex Environmental Corporation, Research Triangle Park, North Carolina, U.S.A.
2U,S. Environmental Protection Agency, Air Pollution Prevention and Control Division,
Research Triangle Park, North Carolina, U.S.A.
ABSTRACT
The U.S. Environmental Protection Agency (EPA) Air Pollution Prevention and Control
Division (APPCD) has performed testing for products with different surface and mass transfer
characteristics to evaluate the application of the Field and Laboratory Emission Cell (FLEC)
for field studies. The goal of these tests has been to gain a better understanding of the effects
of the FLEC operating parameters (e.g., high air exchange, high loading, low velocity).
During recent tests, the impact of relative humidity (RH) on emissions from latex paint applied
to gypsum board was investigated because RH may impact how the FLEC could be used in
field studies. Dynamic emissions tests in small (53-1) chambers showed that RH levels in the
chamber affected emissions of ethylene glycol, but had little impact on Texanol. The data
suggested that the FLEC must be used with a humidified air source, which was demonstrated
in a subsequent experiment. When operated with supply air at 50% RH, emissions
measurements for ethylene glycol with the FLEC were comparable to results with small
chambers, but Texanol measurements suggested that further evaluations are required.
INTRODUCTION
The Field and Laboratory Emission Cell (FLEC) was introduced to the indoor air research
community approximately 5 years ago by Wolkoff et al. (1), Since then it has been shown to
be a useful tool for measuring emission rates from a variety of indoor pollutant sources (2).
The FLEC is a stainless steel disk with a lathed cavity having an internal diameter of 0.15 m
and a volume of 3.5 x 10"5 m3. A silicone foam O-ring seals the cell to the source integrating a
surface area of 0.0177 m2. It can be used for testing in a laboratory, but because it is portable
its most useful application may be for onsite field emissions measurements.
It is well-recognized that the conditions used during emissions testing may have a significant
impact on the emission rates. This is true of any type of test device, whether it be a small
chamber, large chamber, or the FLEC. Operating parameters must be evaluated for each type
of test method and source to be tested Wolkoff et al . (1, 2) have evaluated the impact of
various test parameters during validation of the FLEC. They have evaluated the effect of air
exchange rate, air velocity, and loading factor in tests with the FLEC and by comparison to
234-1 chamber testing. Other parameters, such as temperature and relative humidity (RH), may
also affect emission rates. The effect of RH on emission rates from latex paint applied to
gypsum board was of concern because use of the FLEC with low-cost dry air sources such as a
compressed gas cylinder, although attractive from a standnoint of cost and ease-of-use, may
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result in inaccurate measurements of emission rates.
Testing performed by the EPA has demonstrated a substantial effect of relative humidity for
latex paint emissions in small (53-1) test chambers. In this work, tests were run with the FLEC
to compare with small chamber results. The small chamber tests provide a better established
and understood test method that can provide a point of comparison to demonstrate the
applicability of the FLEC.
METHODS
Emissions tests were conducted in the EPA APPCD Source Characterization Laboratories
using small (53-1) stainless steel chambers following established APPCD methods (3). The
effect of RH was evaluated by performing 14-day tests in the small chambers using three
different inlet relative humidity levels (at 23 °C). Emissions with the FLEC were evaluated in
the laboratory at 50% RH and with dry air. Test conditions are described in Table 1.
Table 1 Test parameters for latex paint experiments with the FLEC and 53-1 chamber
Parameters
53-1
Low
RH
53-1
Medium
RH
53-1
High
RH
FLEC
Dry air
FLEC
Medium
RH
RH Inlet (%)
24
50
78
~4
50
Temperature (°C)
23
23
23
23
23
Air Exchange Rate (h"1)
0.5
0.5
0.5
516
571
Loading (m2/m3)
0.48
0.48
0.48
506
506
Wet Film Thickness(^m)
107
104
96
105
105 .
Ail tests were conducted using a single lot of flat latex paint and standard construction grade
gypsum board purchased from a local retail outlet. The paint was applied with a standard paint
roller.
For the 53-1 chamber emission tests, the paint was applied to the gypsum board substrate and
immediately placed in the chamber. The tests at low and high RH were performed over 2-
week test periods. In other tests with the RH at 50%, emissions have been monitored for over
4000 hours (167 days). The FLEC test to compare use of dry air to supply air at 50% was
conducted by mounting the FLECs on a piece of gypsum board that had been painted 1380
hours (58 days) prior to the test.
For field use of the FLEC, a test was conducted at APPCD's Indoor Air Quality Test House, a
3-bedroom ranch house maintained for conducting indoor air experiments. The test was
conducted by placing the FLEC on a bedroom wall that had been painted 1512 hours (63 days)
prior to the test. In the field test, the FLEC was mounted vertically in the center of the
bedroom wall. Clean air was supplied to the FLEC at 23 °C and 50% RH during the test.
Air samples were collected on Tenax TA sorbent tubes during all tests. Texanol, 2-(2-
butoxyethoxy)ethanol (BEE), ethylene glycol, and propylene glycol were quantified by gas
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chromatography/flame ionization detection (GC/FID) (3,4). The emission factors for
individual VOCs were directly calculated from the concentration data (5).
RESULTS AND DISCUSSION
Small chamber tests of the effect of relative humidity
Small chamber emission tests were conducted at low (24%) and high (78%) RH, and the
results were compared to emissions measured under the standard test conditions of 50% RH
(at 23 0 C) in the air supplied to the chamber (inlet air). The effect of the inlet RH on ethylene
glycol and Texanol emissions is shown in Figures 1 and 2, respectively. There was a moderate
effect of RH on the Texanol emissions during the 350 hour test period. The effect was much
more substantial for ethylene glycol. As shown in Figure 1, the peak concentration of ethylene
glycol was higher at the low RH, but after the first 12 hours, emissions of ethylene glycol were
higher in the chamber with the higher RH.
ioo r
so r
24V» RH 79% RH
£
m
E
e
8
|
C
%
0.2-
100 150 200 2SO 300 350
Eiapitd time, hours
100
24% RH 79% RH
30
m
E
i
i
c
«•
§
0.03
0.01
300
350
Figure I Effect of RH on ethylene glycol Figure 2 Effect of RH on Texanol emissions
emissions from latex paint in small chamber from latex paint in small chamber tests,
tests.
The impact of RH on peak concentrations is shown in Table 2. The peak concentration of
ethylene glycol in the low RH test was 2.7 times higher than that in the high RH test. The
peak concentration of propylene glycol was also substantially higher. RH, however, seemed to
have little effect on the peak concentrations of Texanol or BEE. Despite higher peak
concentrations of the glycols in tests at low RH, the total glycol emissions over the 2-week test
were substantially lower at low RH, as shown in Table 3. The percent of the mass applied that
was emitted during the first 2 weeks at low RH was less than half of that at the high RH for the
glycols. There was no substantial difference for Texanol emissions at the different RH levels.
The low percentage of the applied mass emitted from latex paint on gypsum board is related to
a strong substrate effect that has been reported previously (3). The effect of RH is most
substantial for the glycols, the compounds that are affected most by the substrate effect (3).
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Table 2 Effect of relative humidity on peak concentrations (mg/m3)
of VOC emissions from latex paint applied to gypsum board.
Compound
Low RH
(24%)
Medium RH
(50%)
High RH
(78%)
Ratio of
Low/High
Ethylene glycol
18.4
8.95
6.76
2.7
Propylene glycol
3.11
2.04
1.61
1.9
BEE
6.34
5.31
4.66
1.4
Texanol
17.5
17.2
17.9
1.0
Table 3 Effect of relative humidity on percent of total mass emitted from latex paint
applied to gypsum board during a 2-week test period.
Compound
Low RH
(24%)
Medium RH
(50%)
High RH
(78%)
Ratio of
Low/High
Ethylene glycol
8.2
12
18
0.46
Propylene glycol
7.1
17
22
0.32
BEE
11
13
18
0.61
Texanol
33
27
30
1.1
Effect of RB on FLEC emission measurements
The results of small chamber emission tests at different RHs suggested that the FLEC should
not be used in field studies of latex paint with a dry air source. To evaluate the impact of RH
on field measurements with the FLEC, two FLECs were placed side by side on a piece of
gypsum board that had been painted with the same latex paint 1364 hours prior to the FLEC
test. Dry inlet air (approximately 4% RH) was used for FLEC Ml. FLEC #2 was operated
with supply air at 50% RH. Emissions samples were collected 24, 150, and 194 hours after
placing the FLECs on the test substrate. As shown in Figure 3, the emissions measurements
were substantially different for the two FLECs. Emission rates with the FLEC operated at
50% RH were comparable to previous FLEC and small chamber experiments, but were an
order of magnitude lower when the FLEC was operated with dry air. To verify that the
observed differences were an effect of humidity and not some other operating parameter, the
air supplies were switched at 1581 elapsed hours, so that FLEC #1 was operated with inlet air
at approximately 4% RH and FLEC #2 was operated with inlet air at 50% RH. Another
sample was collected after 94 hours. As shown in Figure 3, switching the air supplies
confirmed the effect of RH on ethylene glycol emissions from the latex paint.
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1
% 0.5
« „ •
£ 03
| 0-2
«
t 0.1
c
g
§ 0.05
y
0.03
0.02
WOO	1,400	1300	1,600	1,700
Elapsed time, hours
Figure 3 The effect of the change in the inlet air
supply to the FLEC for ethylene glycol emissions from
latex paint.
FLEC I
FLEC 2
JL
Application of the FLEC for field measurements
The FLEC was subsequently used at the EPA Indoor Air Quality Test House to measure
emissions from latex paint that had been applied to gypsum board approximately 1500 hours
(62.5 days) prior to the measurement. A humidified air source (23° C and 50% RH) was used
to supply air to the FLEC. Results from the test were compared to previous laboratory tests
with the FLEC for the same type and lot of paint and gypsum board and to interpolation
predictions from small chamber data. Results of the comparison are presented in Table 4.
Measurements of emissions with the FLEC at the test house agreed reasonably well for
ethylene glycol and BEE with previous laboratory FLEC tests and predictions based on small
chamber test data Propylene glycol data agreed to a lesser extent. The small differences
between the FLEC tests and the small chamber test may be related to variability in the
substrate and paint applications, test conditions, and variability associated with the sampling
and analysis method. However, as shown in the table, predicted Texanol emission rates were
nearly four times higher than the laboratory FLEC measurements. The reasons for the
differences are not known. Additional testing is required to better determine the relationship
between emissions measurements with the FLEC and small chamber measurements.
Table 4 Emission factor comparison at 1500 elapsed hours (mg/m2-h)
Test ID
Propylene
Glycol
Ethylene
Glycol
BEE
Texanol
Field FLEC Experiment*
0.0094
0.21
0.018
0.0041
Laboratory FLEC Experiment No. 1
0.01E
0.28
0.021
0.0044
Laboratory FLEC Experiment No. 2
0.023
0.35
0.012
0.0046
53-1 Chamber Experiment
0.018
0.23
0.013
0.017
a Average of duplicates collected 24 hours after FLEC setup (1500 hours after paint
application).
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SUMMARY
Small chamber emissions tests demonstrated that the RH used during testing can have a
substantial impact on the emissions measured from latex paint applied to gypsum board both in
small chamber tests and when using the FLEC. RH affected both peak emission concentrations
and total emissions over a 2-week test period. The effect was more substantial for ethylene
glycol and propylene glycol than for BEE. This effect may be due to the hydrophilic properties
of the two glycols. There was little effect on Texanol.
The results of these limited tests indicate that, if the FLEC is used for field measurements, the
impact of RH in the supply air must be considered. The results clearly indicate that use of a
dry air source, such as a cylinder of compressed zero air, would not be suitable and will likely
result in inaccurate measurement results. Additional research is required to more fully
understand the impact of RH on emissions of VOCs from latex paint on gypsum board and for
other indoor air pollutant sources.
REFERENCES
1.	Wolkoff, P., Clause, P.A., Nielsen, P.A., Gustafsson, H.,Johnson, B., and Rasmunsen, E.,
"Field and Laboratory Emission Cell: FLEC," Healthy Buildings '91. 1991, pp. 160 - 165.
2.	Wolkoff, P., Clause, P.A., Nielsen, P.A,, and Gunnarsen, L., "Documentation of Field and
Laboratory Emission Cell "FLEC" - Identification of Emission Processes from Carpet,
Linoleum, Paint and Sealant by Modelling," Indoor Air '93. Proceedings of the 6th International
Conference on Indoor Air Quality and Climate, Vol. 2, Helsinki, Finland, 1993, pp. 549-554.
3.	Krebs, K, Lao, H., Fortmann, R , and Tichenor, B., Test Methods for Determining Short
and Long Term Emissions from Latex Paint, Proceedings of the Air and Waste Management
Association Engineering Solutions to Indoor Air Quality Problems, VIP 51, 1995, pp. 71-81.
4.	Roache, N., Guo, Z , Fortmann, R, and Tichenor, B. Comparing the Field and Laboratory
Emission Cell (FLEC) with Traditional Emissions Testing Chambers, Proceedings of the
ASTM Symposium on Methods for Characterizing Indoor Sources and Sinks, Washington,
D C., September 1994.
5.	Roache, N. and Howard, E. Characterization of the Usefulness of the Field and Laboratory
Emission Cell (FLEC) for the Evaluation of Emissions from Engineered Wood Products,
Proceedings of the Air and Waste Management Association Engineering Solutions to Indoor
Air Quality Problems, VIP 51, 1995, pp. 51-60.
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„TD D n TECHNICAL RETORT DATA
iNxtlVXrtl-/- rt 1 r~ tr~ J.UI (Please read Instructions on the reverse before complel
1, REPORT NO. 2,
EP A/600/A-97/006
3.
4. TITLE AND SUBTITLE
Observations on Application of the Field and Labora-
tory Emission Cell (FLEC) for Latex Paint Emis-
sions— Effect of Relative Humidity
S. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
N. Roache (A cur ex), E. Howard (EPA), Z. Guo (A cur ex),
and R.Fortmann (Acurex)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING OROANIZATION NAME ANO AOORESS
Acurex Environmental Corporation
P. O. Box 13109
Research Triangle Park, North Carolina 27709
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D4-0005, Task 2-011
12. SPONSORING AGENCY NAME ANO ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVEREO
Published paper; 7/94-3/96
14. SPONSORING AGENCY CODE
EPA/600/13
is. supplementary notes ^ppQj-) project officer is Elizabeth M. Howard, Mail Drop 54,
919/541-7915. Presented at 7th International Conference on Indoor Air Quality and
Climate. Naeova. Jaoan. 7/21-26/96.
«.abstract paper describes tests for products with different surface and mass
transfer characteristics to evaluate the application of the Field and Laboratory
Emission Cell (FLEC) for field studies. The test goal was to better understand the
effects of the FLEC operating parameters (e.g., high air exchange, high loading,
low velocity). During recent tests, the impact of relative humidity (RH) on emis-
sions from latex paint applied to gypsum board was investigated because RH may
impact how the FLEC can be used in field studies. Dynamic emissions tests in
small (53~L) chambers showed that RH levels in the chamber affected emissions of
ethylene glycol, but had little impact on Texanol. The data suggested that the FLEC
must be used with a humidified air source, which was demonstrated in a subsequent
experiment. When operated with supply air at 50% RH, emissions measurements for
ethylene glycol with the FLEC were comparable to results with small chambers, but
Texanol measurements suggested that further evaluations are required.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b,IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Latex
Paints
Emission
Humidity
Measurement
Pollution Prevention
Stationary Sources
Latex Paint
Field and Laboratory
Emission Cell (FLEC)
13	B
11J
lie, 13 C
14	G
04B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)

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