United States
Environmental
Protection
Agency
Office of
Research and
Development
Washington DC 20460
Air and Energy
Engineering
Research Laboratory
Research Triangle Park NC 27711
EPA/600/F-95/005
February 1995
&EPA Indoor Air Research
Characterizing Air
Emissions from Indoor Sources
Paints &
Other Coatings
MotrN
Crystals
Fresh
Dry
Carpeting Cleaning
Heating &
Cooling
System
Adhesives & Glues
Aerosols
Biocontamiinants
Consumer Products
Solvents
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Research conducted by AEERL has been the basis for
better understanding the relationship between emission
sources and indoor air quality. This information can
ultimately provide practical methods that builders,
architects, manufacturers, and the public can use in
selecting and manufacturing indoor materials and
products for improved indoor air quality.
Background
Several recent studies by the U.S. Environmental
Protection Agency (EPA) have identified indoor air
pollution as one of the most important environmental
risks to the Nation's health.1'2 This high risk from
exposure to indoor air pollution reflects the elevated
concentrations of indoor contaminants, the large number
of people exposed to indoor air pollution, and the
amount of time spent indoors (it is estimated that people
spend as much as 90% of their time indoors).
A 1987 EPA report1 ranked indoor air pollutants as the
fourth highest risk in a list of nearly 30 environmental
problems. A 1990 followup study by ERA'S Science
Advisory Board also identified indoor air pollution as a
prime candidate for more aggressive risk reduction
strategies.2
The risk from exposure to indoor air pollution is
supported by a series of long-term EPA studies of
human exposure to indoor air pollutants.3 Major findings
from these studies are:
For many pollutants, indoor levels are 2-5 times
higher than outdoors;
In both rural and heavily industrialized areas,
personal exposures and indoor concentrations
exceed outdoor air concentrations for essentially all of
the prevalent volatile organic compounds;
After some activities, indoor air pollutant levels can be
up to 1,000 times higher than outdoors; and
In new non-residential buildings, levels of volatile
organic compounds can be as much as 100 times
higher than outdoors.
Why Is Indoor Air Pollution a Problem?
With the advancement of modern technology, the
numbers and types of contaminants released into the
indoor environment have increased dramatically. This
trend is due to a number of factors including: the
construction of well-sealed buildings, the use of
synthetic building materials and furnishings, and the
use of chemically formulated personal care products,
pesticides, and household cleansers. Additionally, while
the number of contaminants used indoors has
increased, the amount of outdoor air that is supplied for
ventilation has decreased in many buildings.
Health effects from exposure to indoor air pollution
range from eye, nose, or throat irritation to fatal effects
such as cancer or carbon monoxide poisoning. In
addition to the health risks associated with poor indoor
air quality (IAQ), indoor air pollution also has economic
effects. These include: lost worker productivity, direct
medical costs, and materials and equipment damage.
Many indoor sources have been implicated as causes of
indoor air pollution (Figure 1 ).4 Combustion sources
(e.g., cigarettes, gas ranges) emit nitrogen dioxide,
carbon monoxide, and organics. Natural sources can
cause elevated levels of radon and biocontaminants.
Building materials, furnishings, and consumer products
also emit a wide variety of organic compounds and fine
particulates.
Evaluation of indoor air pollution requires an
understanding of the relationship among indoor air
sources, air movement, and air exchange with the
outdoors.
What Is EPA Doing About Indoor Air Pollution?
Currently, EPA is addressing indoor air pollution through
non-regulatory approaches. EPA's Office of Radiation
Moth
Crystals
Fresh
Dry
Carpeting Cleaning
Adhesives & Glues
Aerosols
Biocontaminants
Consumer Products
Solvents
Figure 1. Examples of Air Pollution Sources in the Home.
Printed on Recycled Paper
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Improved Technology for En
and Indoor Air addresses policy issues, develops
guidance, and conducts training and public outreach
activities (e.g., the IAQ Information Clearinghouse).
To address research issues related to IAQ, EPA's Office
of Research and Development (ORD) has developed a
comprehensive Indoor Air Research Program. This
research emphasizes: (1) improving the scientific
understanding of indoor air pollution health risks and
techniques to reduce these risks, (2) providing critical
scientific information to EPA Program Offices and
Regions in support of developing, implementing, and
evaluating risk management options, and (3) promoting
private sector involvement in identifying, understanding,
and addressing important indoor air pollution problems.
EPA's Indoor Air Research Program is divided into five
multidisciplinary areas (Figure 2):
Source Characterization- What is the nature of the
emitted material, and how does it contribute to human
exposure? Source characterization research is
conducted by the Air and Energy Engineering Research
Laboratory (AEERL).
Exposure Assessment- How many people are
exposed to what levels of pollution? Exposure
assessment research, including indoor air monitoring
and building studies, is conducted by the Atmospheric
Research and Exposure Assessment Laboratory
(AREAL).
Health Effects- What is the quantitative relationship
between exposure/dose and adverse health effects in
people? Research on the health effects of exposure to
Exposure
Assessment
Health Effects
Prevention/
Mitigation
Risk
Assessment
indoor air is conducted by the Health Effects Research
Laboratory (HERL).
Risk Assessment- What are the likelihood and
magnitude of health risks associated with indoor air
pollution? Assessment of risk is provided by the
Environmental Criteria and Assessment Office (ECAO).
Prevention/Mitigation- What control strategies are
most cost-effective in preventing/reducing exposure?
Mitigation research to eliminate or reduce exposure to
indoor air pollution is conducted by AEERL.
This brochure provides an overview of AEERL's source
characterization research. The overall objectives of this
research program are: (1) to gain a sufficient
understanding of indoor air source emissions and
pollutant transport to assist with the development of IAQ
source management options, and (2) to provide practical
methods that builders, architects, and manufacturers
can use in selecting and manufacturing indoor materials
and products. These objectives are accomplished
through:
Test Method Development,
Emission Model Development,
Understanding Fundamental Mass Transfer
Processes,
Program Office Support Projects, and
Technical Assistance to Public and Private
Organizations.
Indoor Air Source Characterization
Understanding the emission characteristics of different
indoor sources over time is a critical first step in devising
the most appropriate IAQ source management strategy
(hypothetical example in Figure 3).
Figure 2. Five Components of EPA's Indoor Air Research
Program.
Figure 3. Example of Source Decay Rate on Indoor Air
Pollution Levels at Constant Ventilation,
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When EPA began its indoor air research program,
information about the sources and emissions of organics
into the indoor environment was limited. To better
understand source emissions, AEERL developed
measurement methods that use small environmental
chambers to test a variety of materials and products.
This research resulted in the development of test
guidance: Using Small Environmental Test Chambers to
Characterize Organic Emissions from Indoor Materials
and Products.5 In 1990, the American Society of Testing
and Materials (ASTM) published this information as a
guide.6
This test methodology is now widely used by both the
private and public sectors in the U.S. and internationally
for characterizing organic emissions from indoor
materials and products. In the U.S., manufacturers of
office furniture, carpets, and adhesives are using the
test methods to evaluate their products and provide
emissions information to architects and consumers. The
State of Washington requires suppliers of building
materials and furnishings to include emissions data in
their bids for new State office buildings. Overseas, the
European Economic Community (EEC) has adopted the
AEERL test methods as an integral part of their
publfshed testing program.
AEERL's Source Characterization Research
AEERL's source characterization research follows an
integrated three-phase approach consisting of small
chamber tests, IAQ modeling, and full-scale test house
studies (Figure 4). Emission tests are conducted in the
small chamber. Then, an IAQ model developed by
AEERL is used to calculate indoor pollutant
concentrations based on chamber emission data and
the air exchange and air movement within the indoor
environment. An IAQ test house is then used to conduct
experiments to evaluate the model results and better
understand room-to-room transport of indoor contami-
nants. The small chamber tests are discussed below.
Small Chamber Tests- Small environmental chambers
are used to generate source emission factors for specific
indoor pollutants. AEERL's small chamber facility
includes a clean air delivery system, test chambers (53
and 166 liters, constructed with nonadsorbent polished
stainless steel interiors, and well-mixed), environmental
controls (temperature, humidity, and air flow rate), and
sampling and analysis equipment.7 Emissions are tested
by placing a sample in the chamber and measuring the
concentration at the chamber outlet. Concentration data
are collected over a sufficient time interval to adequately
describe the typical behavior of the sample. Product
J,
71
Chambers
-Controlled Experiments
-Evaluate Environmental
Variables
-Develop Source Emission
Factors
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IAQ Test House
Model
-Air Exchange -Full Scale Testing
-HVAC Operation -Room-to-Room
Transport
-Sources and Sinks
-Model Validation
-Predict Indoor
Concentration
Figure 4. AEERL's Three-Phase Approach to Source Charac-
terization Research.
loading (area of sample/volume of test chamber) and
the age and condition of the sample are critical for an
accurate determination of emission rates.
AEERL researchers have studied emissions from a
variety of indoor materials and products (Table 1). These
materials are categorized as either wet or dry sources
and/or as sinks. Wet materials include a wide variety of
architectural coatings, eidhesives, caulks, and sealants.
Such materials are applied wet, and their emissions are
relatively high initially and decay rapidly over time. Dry
materials, which include the majority of materials used
to construct and furnish residential and commercial
buildings, are characterized by lower emission rates
which decay slowly. Sinks are indoor materials that
adsorb emissions from other materials and products,
later reemitting the contaminants. AEERL also
researches indoor biocontaminant emissions.
Researching the Behavior of Indoor Sinks- The
interaction of indoor air pollutants with interior surfaces
(i.e., sinks) is a well known, but poorly understood
phenomenon. When volatile organic compounds (VOCs)
are initially emitted from various sources, indoor
concentrations are high, and indoor sinks adsorb the
pollutants. As the source emissions decrease over time,.
the indoor concentrations also decrease. However, re-
emissions of the VOCs from the sinks reduce the rate of
decay of the indoor concentrations. Thus re-emissions
from indoor sinks cause exposures to higher
concentrations of VOCs than would occur in the
absence of sinks.
Research is being conducted by AEERL using the small
environmental test chambers and the test house to
develop data for predicting sink behavior. Experiments
have determined the magnitude and rate of adsorption
and desorption of VOCs for several materials commonly
found indoors (Table 1).
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Table 1. Examples of Indoor Sources and Sinks Studied by AEERL
Wet
Sources
Dry Sources
Sinks
Construction Materials- caulk, floor adhesive, general purpose adhesive
Paints/Coatings- wood stain, polyurethane, architecural coatings
Consumer Products- wood floor wax, spot remover
Materials & Furnishings- particleboard, carpets, room divider panels, floor tile, dry-cleaned
clothes, moth crystals
Materials- painted gypsumboard, ceiling tile, window glass, duct liner
Furnishings- carpet, upholstery
This research is providing a quantitative description of
the interaction between sink materials and indoor
organic vapors. It couples classical adsorption theory
with experimental data and has produced the first
published quantitative results on the magnitude and
rates of adsorption/desorption for VOCs and indoor
surfaces.
The practical application of the results is demonstrated
by using them in an IAQ model to predict concentration
vs. time for organics and comparing the predicted
results from the model with data from a test house
(Figure 5). This close coupling of fundamental mass
transfer theory, laboratory experiments, an IAQ model,
and test house experiment forms the foundation for
additional research on the effects of sinks on IAQ.
Accomplishments/Impacts
AEERL's major accomplishments have been the
development of test methods for characterizing indoor
air sources, preparation of the Environmental Resource
Guides, understanding the behavior of indoor sinks,
1000
" IAQ Model Prediction
"No Sink" Prediction
100
200 300
Time (h)
400
500
Figure 5. IAQ Test House Experiment Demonstrating the Sink
Effect.
development of an IAQ model, and providing technical
guidance and support.
Development of Test Methods- AEERL has
established a level of internationally recognized
expertise in the development of test methods for
characterizing indoor sources. These methods focus on
vapor-phase organic compounds and are applicable to a
wide variety of indoor materials and products. In 1990,
the American Society for Testing and Materials (ASTM)
published AEERL's small chamber methodology as a
guide, Small Scale Environmental Chamber
Determinations of Organic Emissions from Indoor
Materials and Products.6 This guidance can be used by
industry for product development and/or evaluation; by
the private sector for materials testing and selection;
and by EPA or other regulatory agencies or building
code writers to help improve the quality of indoor air.
Methods developed by AEERL are currently being used
by industry, academia, and the international community
(e.g., the European Economic Community).
Environmental Resource Guide (ERG)- The ERG is a
comprehensive, environmentally focused architectural
resource document being developed under a
cooperative agreement with the American Institute of
Architects. The primary purpose of the ERG is to
provide technical information on a range of Life Cycle
Assessment (LCA) issues to architects and other design
professionals to facilitate their ability to evaluate the
environmental impacts of their design decisions and
specifications. Indoor sources that impact IAQ are a
major component of the LCA impacts addressed.
Consequently, the ERG has become an important
vehicle for the dissemination of AEERL's expertise on
source characterization and indoor air modeling.
Understanding Indoor Sinks- AEERL's research has
resulted in: (1) the development of experimental
methods for evaluating indoor sinks; (2) the
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quantification of sink effects in an indoor environment;
and (3) the incorporation of sink effects into an IAQ
model. These contributions extend the state-of-the-
art beyond the purely empirical approaches previously
published. These results also provide researchers with a
foundation to guide future studies of sinks and
practitioners with guidance for analyzing the role sinks
play in indoor environments.
Development of IAQ Model- AEERL's IAQ model is
used to calculate indoor pollutant concentrations based
on chamber emission data, air exchange, and air
movement. Several hundred copies of the IAQ model
have been distributed.8
Providing Technical Guidance and Support-
Technical guidance on the use of small environmental
test chambers to characterize organic emissions from
indoor materials and products has been provided to
several public and private organizations, including:
Industry- Allied Fibers, Amway, Armstrong, BASF, Ciby-
Geigy, Dupont, Georgia-Pacific, Interface, Johnson Wax,
and Monsanto.
Industry Groups- American Particleboard Association,
Carpet and Rug Institute, and Textile Manufacturers
Association.
Consultants and Researchers- Air Quality Sciences,
Geomet, Georgia Tech, Lawrence Berkeley Laboratory,
Lockheed, Research Triangle Institute, and Underwriters
Laboratories.
international- Australia, Canada, Denmark, Finland,
France, New Zealand, and Sweden.
AEERL has also provided extensive technical support to
EPA Program Offices. As a result, AEERL's research
efforts have been applied to real-world indoor air
problems. Examples include evaluation of:
EPA Headquarters (Waterside Mall) Carpet and
Office Partitions,
Materials and Furnishings for New EPA
Headquarters Building,
Perchloroethylene Emissions from Dry Cleaning,
Mercury Emissions from Latex Paint,
Chemical Emissions and Bioresponse from Carpet
Emissions (with the Health Effects Research
Laboratory), and Test Methods for Measuring
Emissions from Carpets and Paints.
Publications/Presentations
Results from AEERL's source characterization research
are communicated to the public through a variety of
media. Over 40 presentations have been given at
technical conferences and symposia; over 30 technical
papers and reports have been published.
AEERL also routinely provides facility tours for industry
and other researchers who are interested in the test
method developed by AEERL (see "Providing Technical
Guidance and Support").
Future Plans
Over the next 5 years, AEERL's source characterization
research will focus on:
Customizing the small chamber method to determine
vapor emissions for other sources including: latex
paints, oil-based paints, other architectural coatings,
adhesives, resilient floor covering, and waxes/
polishes,
Developing standard methods for testing
activity based sources (e.g., paints) in a new large
chamber test facility,
Developing standardized methods that can be used to
conduct fundamental biocontaminant research and
evaluate the effects of temperature, humidity, light,
dust, and substrate material on biocontaminant
growth, and
Supplementing available source emission data
through research and through cooperation with the
private sector to broaden the available database and
to validate and quality assure the data.
For more information contact:
Mike Osborne
Indoor Air Branch (MD-54)
Air & Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
phone: 919-541-4113; fax 919-541-2157.
References
1. U.S. EPA, Office of Policy, Planning and Evaluation,
"Unfinished Business: A Comparative Assessment
of Environmental Problems," See EPA-230/2-87-025
(NTIS PB88-127030), 1987.
2. U.S. EPA, Science Advisory Board, "Reducing Risk:
Setting Priorities and Strategies for Environmental
Protection," 1990.
3. U.S. EPA, Total Exposure Assessment Methodology
(TEAM) Study. (NTIS PB88-100052)
4. Tichenor, B.A. and Mason, M.A., Organic
Emissions from Consumer Products and Building
Materials to the Indoor Environment, JAPCA, 38: pp.
264-268,1988.
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5. Tichenor, B.A., Indoor Air Sources: Using Small
Environmental Test Chambers to Characterize
Organic Emissions from Indoor Materials and
Products, EPA-600/8-89-074 (NTIS PB90-110131)
August 1989.
6. Small-Scale Environmental Chamber
Determinations of Organic Emissions from Indoor
Materials and Products, ASTM Standard Guide
D5116-90.
7. Tichenor, B.A., Characterizing Material Sources and
Sinks-Current Approaches, Annals of New York
Academy of Science, Vol. 641: pp. 63-78,1992.
8. Sparks, LE. "EXPOSURE Version 2: A Computer
Model for Analyzing the Effects of Indoor Air
Pollutant Sources on Individual Exposure," EPA-600/
8-91-013 (NTIS PB91201095), April 1991.
GOVERNMENT PRINTING OFFICE: 1995 - 650-006/00246
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