United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-01/093 January 2002
Capstone Report on the
Development of a Standard Test
Method for VOC Emissions from
Interior and Alkyd Paints
JohnC. S.Chang
The report gives details of a small-
chamber test method, developed by
EPA for characterizing volatile organic
compound (VOC) emissions from inte-
rior latex and alkyd paints. Current
knowledge about VOC, including haz-
ardous air pollutant, emissions from in-
terior paints generated by tests based
on this method are presented. Experi-
mental data were analyzed to demon-
strate the usefulness of the method and
test results in terms of emission char-
acterization, material selection, expo-
sure assessment, and emission
reduction by product reformulation. The
conclusions drawn from the experimen-
tal results were used to develop a stan-
dard practice to be adopted by the
American Society of Testing and Ma-
terials (ASTM). The draft standard prac-
tice is presented as an appendix to the
full report.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Americans spend about 90% of their
time indoors, where concentrations of
pollutants are often much higher than they
are outdoors. It is not surprising, there-
fore, that risk assessment and risk man-
agement studies have shown that indoor
environmental pollution poses significant
risks to human health.
The U.S. Environmental Protection
Agency (EPA) has evaluated a number of
indoor materials and products as poten-
tial sources of indoor air pollution under
the Indoor Air Source Characterization
Project (IASCP). Interior architectural coat-
ings, especially alkyd and latex paints,
were identified as potentially high-risk in-
door sources by the Source Ranking Da-
tabase developed under the IASCP. EPA
conducted a literature survey and found
that there was a lack of reliable and con-
sistent paint emission data for develop-
ing and evaluating risk management
options. Further investigation showed that
a standardized test method needed to be
developed so that testing laboratories, re-
searchers, and paint manufacturers could
generate and report emission data that
were complete, consistent, and compa-
rable.
Between 1995 and 1999, EPA's Na-
tional Risk Management Research Labo-
ratory (NRMRL) conducted a paint
emission characterization research pro-
gram. The program was devoted to de-
veloping, verifying, and demonstrating a
small-chamber test method for the mea-
surement of volatile organic compound
(VOC) and hazardous air pollutant (HAP)
emissions from alkyd and latex paints.
The test method has been documented
and submitted to the American Society
for Testing and Materials (ASTM) for adop-
tion as a standard practice.
The report summarizes the resulting test
method, presents new findings, and de-
scribes the key results generated by
NRMRL as it assessed emissions from
alkyd and latex paints. The report is di-
vided into four parts. After introducing the
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study and providing background informa-
tion about existing literature on the sub-
ject paint emissions testing, the report
describes the developed standard test
method for characterizing organic com-
pounds emitted from paint. It also de-
scribes the results of NRMRL's tests on
alkyd and latex paints.
Standardized Test Method
The standardized test method ad-
dresses the following key issues:
•Storing and handling paint samples
prior to analysis
• Analyzing paint in bulk (as a liquid)
•Selecting and preparing a paint sub-
strate for testing
•[Applying paint to a substrate to cre-
ate a test specimen
•[Establishing and controlling test con-
ditions
•Sampling the VOC emissions from
the painted specimen
•[Analyzing the samples with chemical
instruments
•[Calculating emission rates/factors us-
ing experimental data
• Conducting quality assurance/qual-
ity control
The core experimental apparatus em-
ployed by the standardized test method
is a device called a Small Environmental
Test Chamber ("small chamber" for short).
A test chamber is a hollow box that may
range in size from a few liters to 5 m3.
The chamber used at NRMRL is 53 L
(0.053 m3) in volume. Chambers with vol-
umes greater than 5 m3 are defined as
"large"—they may reach the scale of an
entire room. The small chamber, on the
other hand, is an apparatus suited to the
spatial and financial constraints of a typi-
cal laboratory environment. It is also more
convenient to operate than a large cham-
ber. An environmental chamber test facil-
ity, designed and operated to determine
organic emission rates from paints, should
contain: test chambers, a clean air gen-
eration system, monitoring and control
systems, sample collection and analysis
equipment, and standards generation and
calibration systems. The purpose of these
components is to provide a controlled en-
vironment for conducting emissions test-
ing that can reflect common indoor air
conditions.
The standardized test method includes
a series of procedures and guidelines for
preparing a painted test specimen. Pro-
cedures for handling and storing the paint
to be tested were established to guard
against the possibility of evaporative
losses, stratification, and property
changes. A modified version of EPA
Method 311 was adopted for the bulk
analysis of paints, to facilitate the experi-
mental design of the emissions test and
the selection of sampling and analytical
techniques. Instead of traditional test sub-
strates such as glass, stainless steel, and
aluminum, common indoor materials such
as gypsum board and wood are recom-
mended in the method for creating realis-
tic and representative testing samples.
Either a roller or a brush should be used
to apply the paint to the substrate. A pro-
tocol was developed to quantify the
amount of the paint applied so that the
emission data can be consistent and com-
parable.
The "time zero" for the start of an emis-
sion test is established when the cham-
ber door is closed (immediately after
placing the test specimen inside the
chamber). The small chamber should be
operated to match the actual environmen-
tal conditions at which people paint the
interiors of houses. The standardized
method guides investigators in setting up
their sampling protocols. The instructions
help to ensure that investigators collect
an adequate quantity of chamber air
samples on the appropriate sampling
media. The method describes several
kinds of analytical instruments that can
be used to determine the amounts and
kinds of VOCs in the collected sample.
Data reduction techniques and an ex-
ample of an emission model are included
in the method—it describes the math-
ematical procedures used to convert the
analytical results into emission rates and
emission factors. In addition, the method
provides guidelines for reporting and qual-
ity assurance. These guidelines should
help investigators compile their results in
a consistent and complete fashion that
allows for comparison or repeat emis-
sions testing of similar or new architec-
tural coatings.
Alkyd Paints
Alkyd paint continues to be used in-
doors because it has desirable proper-
ties such as durability, gloss, gloss
retention, and fast drying. NRMRL has
employed the developed standardized
test method to conduct research that char-
acterizes VOC emissions from alkyd paint.
NRMRL used the results of its paint emis-
sions tests to develop source emission
models. These models, in turn, were used
for the assessment of indoor exposure
levels and risk management options.
The first test series that NRMRL per-
formed on alkyd paints was integrated
into the process of developing and vali-
dating its new standard practices for paint
testing. The tests involved one primer and
three alkyd paints. Bulk analysis indicated
that the alkyd primer and two of the three
paints tested contained more than 100
different VOCs, primarily straight-chain
alkanes, with decane and undecane be-
ing the predominant compounds. The third
paint had more branched alkanes. All four
coatings contained low levels of aromatic
compounds. The total VOC content of the
liquid paints ranged from 32 to 42%. Mea-
surements of the total VOC levels in the
liquid coatings by gas chromatography/
mass spectrometry (GC/MS) agreed well
with manufacturers' data.
Mass balance calculations were con-
ducted to compare the bulk analysis re-
sults and chamber emission data to
evaluate the recovery. It was found that
for total VOC, the majority (greater than
80%) of the mass in the applied paint
could be accounted for in the subsequent
air emissions. The data for the more abun-
dant compounds (e.g., nonane, decane,
and undecane) in the paint suggest that
there was a margin of error of + 20% in
measuring these recoveries.
Due to the relatively high VOC content
and fast emission pattern, peak concen-
trations of total VOCs as high as 10,000
mg/m3 were measured during small-cham-
ber emissions tests with a loading factor
of 0.5 m2/m3 and an air exchange rate of
0.5 h-1. Over 90% of the VOCs were emit-
ted from the primer and paints during the
first 10 hours following application.
A series of tests were performed to
evaluate factors that may affect emissions
following application of the coatings. It was
found that the type of substrate (glass,
wallboard, or pine board) did not have a
substantial effect on the emissions with
respect to peak concentrations, the emis-
sions profile, or the mass of VOCs emit-
ted from the paint. The emissions from
paint applied to bare pine board, a primed
board, and a board previously painted
with the same paint were quite similar.
There were differences among the emis-
sions from the three different paints, but
the general patterns of these emissions
were similar. The effect of other variables,
including film thickness, air velocity at
the surface, and air exchange rate, were
consistent with theoretical predictions for
gas-phase, mass-transfer-controlled emis-
sions.
Results from the testing performed in
this study are being used to develop com-
putational methods for estimating the
emission rate of total VOCs from solvent-
based coating products used indoors. The
database on total VOC emission from
alkyd paint should also be useful for oth-
ers involved in model development and
validation.
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In addition to studying the effects of
substrates and other environmental vari-
ables on total VOC emissions, small en-
vironmental chamber tests were
conducted to characterize the emissions
of a toxic chemical compound—methyl
ethyl ketoxime (MEKO)—from three dif-
ferent alkyd paints. The data resulting from
these tests facilitated the development of
a set of risk management options for
MEKO.
MEKO, another name for 2-butanone
oxime or ethyl methyl ketoxime
[CH3C(NOH)C2H5, CAS Registry No. 96-
29-7], is often used by paint manufactur-
ers as an additive to interior alkyd paints.
MEKO has been found to be a moderate
eye irritant. It was also the subject of a
Section 4 test rule under the Toxic Sub-
stances Control Act. A number of toxico-
logical endpoints have been evaluated
by testing conducted under the test rule.
MEKO demonstrated carcinogenic activ-
ity in long-term inhalation studies, caus-
ing liver tumors in both rats and mice.
MEKO acts as an anti-skinning agent
(or anti-oxidant) that prevents oxidative
drying or skinning of the alkyd paint to
improve stability in the can. Usually, the
MEKO content in a paint is less than 0.5%.
Due to its relatively high volatility (its boil-
ing point is only 152 °C), the majority of
the MEKO in the paint is expected to be
released into the surrounding indoor air
after painting to allow the paint to dry
properly on the painted surfaces. The ef-
fects of MEKO emissions on indoor air
quality (IAQ) and associated exposure risk
depend on characteristics such as emis-
sion rates and patterns.
Bulk analysis showed that the MEKO
content in alkyd paints can be as high as
several milligrams per gram. Material bal-
ance from the chamber tests indicated
that the majority (greater than 68%) of the
MEKO in the paint applied was emitted
into the air. MEKO emissions occurred
almost immediately after each alkyd paint
was applied to a pine board. Due to the
fast emission pattern, more than 90% of
the MEKO emitted was released within 10
hours after painting. The peak concentra-
tions of MEKO in chamber air correlated
well with the MEKO content in the paint.
The chamber data were simulated by a
first-order decay emission model that as-
sumed that the MEKO emissions were
mostly gas-phase mass-transfer-con-
trolled. The first-order decay model was
used as an input to the continuous-appli-
cation source term of an IAQ model to
predict indoor MEKO concentrations dur-
ing and after the application of an alkyd
paint in a test house. The predicted test
house MEKO concentrations during and
after the painting exceeded a suggested
indoor exposure limit of 0.1 mg/m3for all
three paints. The predicted MEKO con-
centrations also exceeded the lower limit
of a suggested sensory irritation range of
4 to 18 mg/m3 with two of the three paints
tested. The elevated MEKO concentra-
tions can last for more than 10 h after the
painting is finished. The model was also
used to evaluate and demonstrate the
effectiveness of risk reduction options.
These options involved selecting lower
MEKO paints and establishing higher ven-
tilation levels during painting. The higher
ventilation should be maintained about 2
h after the painting is finished to avoid
exposure to residual MEKO emissions.
In addition to total VOC and MEKO
emissions, the unpleasant "after-odor"
which can persist for weeks after applica-
tion of alkyd paint has been a cause of
IAQ concerns. Three different alkyd paints
were tested in small environmental cham-
bers to characterize the aldehyde emis-
sions. Emission data indicated that
significant amounts of odorous aldehydes
(mainly hexanal) were emitted from alkyd
paints during the air-drying period. Bulk
analyses showed that the alkyd paint it-
self contained no aldehydes. Mass bal-
ance calculations indicated that any
aldehydes emitted should have been pro-
duced after the paint was applied to a
substrate. The aldehydes emission pat-
terns were consistent with the theory that
the aldehydes were formed as byproducts
from spontaneous autoxidation of unsat-
urated fatty acids in the applied paint.
Chamber data showed that the major vola-
tile byproducts generated by the drying of
the alkyd paints were hexanal, propanal,
and pentanal. These results facilitated the
development of an exposure assessment
model for hexanal emissions from drying
alkyd paint.
The hexanal emission rate was simu-
lated by a model that assumed that the
autoxidation process was controlled by a
consecutive first-order reaction mecha-
nism with an initial time lag. The time lag
reflects an induction period after painting
during which little oxygen is taken up by
the alkyd coating. As the final byproduct
of a series of consecutive first-order reac-
tions, the hexanal emission rate increases
from zero to reach a peak and is followed
by a slow decay. This model was con-
firmed by chamber concentration data.
The modeling results also showed that
the hexanal emissions were controlled
mostly by the chemical reactions that
formed intermediates (i.e., the precursors
to hexanal production).
An IAQ simulation that used the emis-
sion rate model indicated that the hexanal
emissions can result in prolonged (sev-
eral days long) exposure risk to occu-
pants. IAQ simulation indicated that the
hexanal concentration due to emissions
from an alkyd paint in an indoor applica-
tion could exceed the reported odor thresh-
old for about 120 hours. The occupant
exposure to aldehydes emitted from alkyd
paint also could cause sensory irritation
and other health concerns.
Latex Paints
The majority (over 85%) of the interior
architectural coatings used in the United
States are latex paints. Previous testing
of latex paint emissions has focused on
determining cumulative mass emissions
of VOCs. The purpose of previous testing
was to assess the effect of these paints
on the ambient air and to determine how
they contributed to photochemical smog.
NRMRL's concern has been to estimate
people's time-varying exposure to overall
VOC levels and to specific VOCs from
indoor latex paints.
The first test series that NRMRL per-
formed on latex paints was integrated into
the process of developing and validating
its new standard practice for paint testing.
NRMRL's small-chamber tests indicated
that the organic emission patterns of la-
tex paints are very different from those of
alkyd paints. Bulk analysis showed that
the total VOC content of a commonly used
latex paint is usually in the range of 2 to
5%, which is considerably lower than that
of alkyd paints (32 to 42%). Instead of
alkanes, alkenes, and aromatics, only
several polar compounds such as gly-
cols, alcohols, and aldehydes were found
in the latex paints.
The chamber test results showed sig-
nificant differences between the emissions
of the same latex paint applied to two
different substrates (a stainless steel plate
and a gypsum board). The amount of
VOCs emitted from the painted stainless
steel was 2 to 10 times greater than the
amount emitted from the painted gypsum
board during the 2-week test period. After
the first 2 weeks, over 90% of the VOCs
were emitted from the paint on the stain-
less steel plate but less than 20% had left
the gypsum board. The dominant species
in the VOCs emitted also changed from
ethylene glycol to 2,2,4-trimethyl-1,3-
pentanediol monoisobutyrate when stain-
less steel was replaced with gypsum
board. Data analysis by a double-expo-
nential model indicated that the majority
of the VOC emissions from the painted
stainless steel could be simulated by an
evaporation-like phenomenon with fast
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VOC emissions controlled by gas-phase
mass transfer. On the other hand, only a
small fraction of the VOCs emitted from
the painted gypsum board appeared to
be controlled by the evaporation-like dry-
ing process. The majority of the VOCs
were emitted after the painted gypsum
board surface was relatively dry. They
were probably dominated by a slow, solid-
phase-diffusion-controlled mass transfer
process. Long-term experimental data in-
dicated that it may take as long as 3.5
years for all the VOCs to be released
from the paint applied to the gypsum
board.
The small-chamber test results demon-
strate that, when the objective of a test is
to provide emissions data that are rel-
evant to understanding a paint's emis-
sions behavior in typical indoor
environments, one should use "real" sub-
strates such as wood and gypsum board
instead of "ideal" substrates such as glass,
aluminum, or stainless steel. Proper
choice of substrate is therefore crucial for
exposure and/or risk assessment studies
involving indoor latex paints.
NRMRL also used the small-chamber
test method to evaluate a relatively new
type of interior architectural coating, the so
called "low-VOC" latex paint. Low-VOC paint
has been used as a substitute for conven-
tional latex paints to avoid indoor air pol-
lution. Low-VOC latex paints are promoted
for use in occupied hospitals, extended
care facilities, nursing homes, medical
facilities, schools, hotels, offices, and
homes where extended evacuation of an
entire building section for painting would
be particularly difficult or undesirable.
Four commercially available low-VOC
latex paints were evaluated as substitutes
for conventional latex paints. They were
evaluated by assessing both their emis-
sion characteristics and their performance
as interior wall coatings. Bulk analysis
indicated that the VOC contents of the four
paints (which ranged from 0.01 to 0.3%) were
considerably lower than those of conven-
tional latex paints (3 to 5%). EPA Method
24 for determining VOC content (com-
monly used by paint manufacturers) is
not accurate enough to quantify the VOC
contents of low-VOC latex paints for qual-
ity control and product ranking purposes.
Other methods such as EPA Method 311
are more suitable, especially when indi-
vidual VOC content data are needed.
The fact that "low-VOC" paint had rela-
tively low VOC emissions was confirmed
by small-chamber emission tests. How-
ever, the experimental data also indicated
that three of the four low-VOC latex paints
tested either had some inferior coating
properties or emitted hazardous air pol-
lutants. Significant emissions of several
aldehydes (especially formaldehyde,
which is a HAP) were detected in emis-
sions from two of the four paints. ASTM
methods were used to evaluate the paints'
coating performance including hiding
power, scrub resistance, washability, dry-
ing time, and yellowing. The results indi-
cated that one of the four low-VOC paints
tested showed performance equivalent or
superior to that of a conventional latex
paint used as control. It was concluded
that low-VOC latex paint can be a viable
option to replace conventional latex paints
for prevention of indoor air pollution. How-
ever, certain paints marketed as "low-
VOC" may still emit significant quantities
of air pollutants, including HAPs. In addi-
tion, some of these paints may not have
performance characteristics matching
those of conventional latex paints.
Due to the use pattern of low-VOC paints
proposed by their manufacturers (i.e.,
partial occupancy during painting and
immediate re-occupation after painting),
the intimate exposure of sensitive occu-
pants to the low-VOC latex paint emis-
sions (especially to HAPs such as
formaldehyde) is of special concern.
Long-term environmental chamber tests
were performed to characterize the form-
aldehyde emission profiles of a low-VOC
latex paint. The formaldehyde emissions
resulted in a sharp increase of formalde-
hyde concentrations within the chamber,
rising to a peak followed by transition to a
long-term slow decay. Environmental
chamber data indicated that formaldehyde
emissions from a low-VOC latex paint can
cause very high (several ppm) peak con-
centrations in the chamber air. When the
paint was applied to gypsum board, the
formaldehyde emissions decayed very
slowly after the initial peak, and the emis-
sion lasted for more than a month. The
results of these tests allowed for the de-
velopment of exposure assessment emis-
sions models to facilitate pollution
prevention efforts to reduce the amount
of formaldehyde released by low-VOC
paints.
A semi-empirical first-order decay in-
series model was developed to interpret
the chamber data. The model character-
ized the formaldehyde emissions from the
paint in three stages: an initial "puff" of
instant release, a fast decay, and a final
stage of slow decay controlled by a solid-
phase diffusion process that can last for
more than a month. The semi-empirical
model was used to estimate the amount
of formaldehyde emitted or remaining in
the paint. It also predicted the initial peak
concentration of formaldehyde and the
time necessary for the formaldehyde to
become depleted from paint. Once the
activity patterns of building occupants
were defined, the model was used for
exposure risk assessment.
Additional small-chamber tests were
performed to investigate the major
sources of formaldehyde in the paint.
Through comparing emission patterns and
modeling outcomes of different paint for-
mulations, a biocide used to preserve one
of the paints was identified as a major
source of the formaldehyde emissions.
Chamber test results also demonstrated
that paint reformulation by replacing the
preservative with a different biocide for
the particular paint tested resulted in an
approximately 55% reduction of formal-
dehyde emissions. However, since other
sources (e.g., additives and binders) of
formaldehyde are present in the paint,
biocide replacement can reduce only the
long-term emissions. Short-term genera-
tion of high concentrations of formalde-
hyde remains a problem. Additional
research is needed to identify other po-
tential sources of formaldehyde to com-
pletely eliminate formaldehyde emissions
from low-VOC paints.
Overall Conclusions
A standard test method was developed
to characterize the VOC, including HAP,
emissions from interior architectural coat-
ings. The advantages of the developed
method and the usefulness of the experi-
mental data it can generate were demon-
strated by extensive tests focused on two
types of commercially available and com-
monly used interior architectural coatings:
latex and alkyd paints. The experimental
data generated by this test method can
be used to estimate emission rates, to
compare emissions from different prod-
ucts, to predict a paint's effects on IAQ
and exposure levels, and to evaluate the
effectiveness of risk management options.
The test method can also be used as a
pollution prevention tool to assist paint
manufacturers in reducing or eliminating
VOC emissions from their products.
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The EPA author, John C. S. Chang, is also the EPA Project Officer (see below).
The complete report, entitled "Capstone Report on the Development of a Stan-
dard Test Method for VOC Emissions from Interior Latex and Alkyd Paints," will
be available at http://www.epa.gov/ORD/NRMRL/Pubs or as Order No.
PB2002-101312; Cost: $44.00subject to change from:
National Technical Information ServiceO
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Telephone: (703) 605-60000
(800) 553-6847 (U.S. only)
The EPA Project Officer can be contacted at:
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U. S. Environmental Protection Agency
Research Triangle Park, NC 27711-0001
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