United States
Environmental Protection
Agency
Air and Energy Engineering ,
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-89/074 Nov. 1989
vvEPA Project Summary
Indoor Air Sources: Using Small
Environmental Test Chambers to
Characterize Organic
Emissions from Indoor
Materials and Products
Bruce A. Tichenor
This report describes methods and
procedures for determining organic
emission rates from indoor
materials/products using small
environmental test chambers. The
techniques presented are useful for
both routine product testing by
manufacturers and testing
laboratories and for more rigorous
evaluation by indoor air quality
researchers.
This Project Summary was devel-
oped by EPA's Air and Energy
Engineering Research Laboratory, Re-
search Triangle Park, NC, to announce
key findings of the research project
that Is fully documented In a separate
report of the same title (see Project
Report ordering Information at back).
Introduction
The use of small environmental test
chambers to develop emission
characteristics of indoor materials and
products is still evolving. Modifications
and variations in equipment, testing
procedures, and data analysis are made
as the work in the area progresses. Until
the interested parties agree upon
standard testing protocols, differences in
approach will occur. The purpose of this
report is to provide assistance by
describing equipment and techniques
suitable for determining organic
emissions from indoor materials. Specific
examples are provided to illustrate
existing approaches; these examples are
not intended to inhibit alternative
approaches or techniques. The
techniques described are useful for both
routine product testing by manufacturers
and testing laboratories and for more
rigorous evaluation by Indoor Air Quality
(IAQ) researchers.
The use of small chambers to evaluate
organic emissions from indoor materials
has several objectives:
developing techniques for screening
products for organic emissions;
determining the effect of environmental
variables (i.e., temperature, humidity,
air exchange) on emission rates;
ranking products and product types
with respect to their emissions profiles
(e.g., emission factors, specific organic
compounds emitted);
providing compound-specific data on
various organic sources to guide field
studies and assist in evaluating IAQ in
buildings;
providing emissions data for the
development and verification of models
used to predict indoor concentrations of
organic compounds; and
developing data useful to
manufacturers and builders for
assessing product emissions and
developing control options or improved
products.
It is emphasized that small chamber
evaluations are used to determine source
emission rates. These rates are then
used in appropriate IAQ models to
predict indoor concentration of the
compounds emitted from the tested
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material. The concentrations observed in
the chambers should not be used as a
substitute for concentrations expected in
full-scale indoor environments.
Facilities and Equipment
A facility designed and operated to
determine organic emission rates from
building materials and consumer
products found indoors should contain
the following: test chambers, clean air
generation system, monitoring and
control systems, sample collection and
analysis equipment, and standards
generation and calibration systems.
Small environmental test chambers are
designed to permit the testing of samples
of various types of building materials and
consumer products. They can range in
size from a few liters to 5 m3. Generally,
chambers of more than 5 m3 are
considered "large". Large chambers
permit the testing of complete
assemblages (e.g., furniture); they may
also be used to evaluate activities (e.g.,
spray painting). For the purpose of this
guide, small chambers are assumed to
be used to test samples of larger
materials and products, as opposed to
full scale materials or processes.
The test chambers should have non-
adsorbent, chemically inert, smooth
interior surfaces. Care must be taken in
their construction to avoid the use of
caulks and adhesives that emit or adsorb
volatile organic compounds. Electro-
polished stainless steel and glass are
common interior surfaces. The chamber
must have an access door with airtight,
non-adsorbent seals. The chambers must
be fitted with inlet and outlet ports for air
flow. Ports for temperature and humidity
probes may also be required. Ports for
sample collection are needed only if the
sampling is not conducted in the outlet
air.
The chambers should be designed to
ensure adequate mixing of the chamber
air. Low speed mixing fans or multi-port
inlet and outlet diffusers are two tech-
niques that have been used successfully.
Clean air must be generated and
delivered to the chambers. A typical
clean air system might use an oilless
compressor drawing in ambient air
followed by removal of moisture (e.g.,
using a membrane dryer) and trace
organics (e.g., by catalytic oxidation
units). Other options include gas
cylinders or charcoal filtered outdoor or
laboratory air. The amount of air flow
required should be calculated before a
decision is reached on the supply
system. The required purity of the air
must also be determined based on the
type of samples to be evaluated.
Measurement and control are required
for air flow, temperature, and humidity.
Air flow can be automatically monitored
and controlled by electronic mass flow
controllers, or manual flow control (e.g.,
needle valve, orifice plate) and
measurement (e.g., bubble meter,
rotometer) can be used. Temperature can
be measured automatically using
thermocouples or thermistors; manual
dial or stem thermometers can also be
used. Control of humidity depends on the
humidification system employed. If liquid
injection is used, water flow is controlled
by the pump setting. Control of humidity
by saturated air requires temperature
control of the water and flow control of
the saturated air stream. Humidity can be
measured using several types of sensors,
including dew point detectors and thin-
film capacitors. Temperature and
humidity sensors should be located
inside the chamber at least 5 cm from the
inside wall and near the midpoint
between the air inlet and outlet ports.
Sample Collection and Analysis
Indoor sources of organic emissions
vary widely in both the strength of their
emissions and the type and number of
compounds emitted. To fully characterize
organic emissions, the sample collection/
analysis system must be capable of
quantitative collection and analysis of
volatile, semivolatile, polar, and non-polar
compounds. Any small chamber
sampling and analysis technique or
strategy developed must consider the
emission characteristics of the specific
source being evaluated. The design and
operation of sample collection and
analysis systems must be appropriate for
the organic compounds (and their
concentrations) being sampled. Such
systems generally include sampling
devices ( e.g., syringes, pumps), sample
collectors (e.g., syringes, adsorbent
media, evacuated canisters), and instru-
ments to analyze organic emissions (e.g.,
gas chromatographs [GCs]).
Experimental Design
The first step in designing an
experiment for chamber tests of indoor
materials/products is to determine the
test objectives. For example, a builder or
architect would be interested in
emissions from a variety of materials to
be used under a given set of conditions
for a specific building. In this case, the
experiment would be designed to handle
many materials with one set of
environmental conditions. A manufacturer
might want to know the emissions^
characteristics of a single product under
both normal and extreme conditions and
would design a test to cover the
appropriate range of environmental
variables. IAQ researchers interested in
the interactions among variables would
use a more complex design involving
ranges of several variables.
A basic experimental design for small
chamber tests should include
consideration of the effects of various
parameters on the emission character-
istics of the materials to be tested. Five
variables are generally considered to be
critical parameters: temperature,
humidity, air exchange rate, product
loading, and time (or product age).
For each material tested, a test matrix
is developed to allow the variables oi
interest to be investigated. As is normal
in experimental programs of this type, the
desire to collect data over an extensive
parameter range is limited by cost anc
time constraints. To maximize the
information production within available
resources, a statistical consultant can b«
used to provide guidance on appropriate
experimental designs.
Experimental Procedures
A preliminary evaluation of th(
product/material is performed to guidi
selection of appropriate test strategie
and analytical techniques. This evaluatioi
is conducted to obtain information on th
specific compounds to be quantified.
only a single compound is to b
quantified, selection of the appropriat
sampling and analysis strategy i
straightforward, and no further screenin
is needed. When a more complet
characterization is desired, mor
information is required. The compositic
of the emissions expected from a sourc
can be evaluated initially by surveyin
available information, including: a) repor
or papers on previous studies of tr
source, b) ingredients listed on th
product label, c) Material Safety Da
Sheets, and d) information obtained fro
the manufacturer or appropriate trac
organizations. Such information is usual
insufficient to identify the compounds
interest, but it does provide son
guidance in what compounds to look f(
Another problem is that the compoum
emitted from the source may be forrrv
during the use of the product or mater
and will not be listed as ingredien
Therefore, further analyses are require
and testing must be conducted
determine the actual compounds bei
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emitted. One technique involves
headspace analysis of the source
emissions.
Headspace Analysis
The process of identifying the organic
compounds present in the "headspace"
or air above the material is termed
"headspace analysis." Both static (i.e.,
closed container) and flow-through
headspace analyses are used.
Headspace components are usually
identified by gas chromatography
coupled coupled with a mass selective
detector (GC/MS) operated in the scan
mode, although other detectors can be
used if sufficient information is available
on the retention times for all compounds
of interest for a given GC column, gas
flow, and temperature program.
While the headspace analysis provides
useful information on the direct emissions
from the material or product of interest, it
does not ensure that all emissions will be
identified. Compounds not found in the
headspace may be emitted later due to
being formed in the drying process or by
interactions with the substrate.
Chamber Testing
Chamber testing requires a preparation
phase as well as a testing phase. The
preparation stage begins with
development of the test plan that
specifies environmental conditions for
each test, method of application of the
material, conditioning period and
methods of sample collection and
analysis. Development of the test plan is
followed by calibration of environmental
control and measurement systems,
sample collection and concentration
devices, and analytical systems as
specified in the Quality Assurance (QA)
Plan. At this stage the information from
the GC/MS headspace analysis is
evaluated to provide guidance in
selection of analytical columns and
detectors, sample collection media and
an appropriate internal standard.
Prior to actual testing, chambers are
cleaned and placed in position in the
temperature controlled environment and
purged at test conditions. Chamber
background is monitored to ensure that
background contamination is within QA
limits. At this point, the chamber
conditions are at test setpoints of flow
and relative humidity, all analytical
systems have been calibrated, the quality
control system has been developed, and
an internal standard has been selected. A
;hamber background sample is then
taken to quantify any contribution of
organic compounds from the clean air
system and/or the empty chamber. In
addition, any substrate materials, such as
wood, that will be used during the tests
must be included to account for actual
background. Once all the preparatory
steps have been completed, testing of
the selected material/product can
commence.
The types of test specimens used in
the chambers vary according to the
material or product being tested. Solid
materials are tested "as is". If emissions
from edges may differ from the normally
exposed surface, the edges should be
sealed. For example, particleboard
specimens can have their edges sealed
with sodium silicate to eliminate the
excessively high edge emissions
previously reported. "Wet" materials are
applied to a solid substrate. For example,
a wood stain would be applied to a board;
a vinyl floor wax to floor tile. As noted
above, the uncoated substrate should be
placed in the chamber during background
tests to determine the magnitude of its
organic emissions. Also edge effects
should be eliminated by edge sealing.
Wet materials are applied to the
substrate outside the chamber and
placed in the chamber shortly thereafter.
The start of the test (time = 0) is set
when the door to the chamber is closed.
Small chambers are not suitable for
evaluating the application phase of wet
material use. Thus, emissions from the
earliest portion of the drying cycle (i.e.,
from application until placement in the
chamber) will not be measured. The time
between application and the start of the
test should be less than ten minutes; the
time of application and the test start time
should both be recorded.
In some cases, emissions data are
desired on later stages of a
material/product life-cycle (e.g., several
months after a coating has been applied).
In these cases, the specimen must be
conditioned prior to testing. Conditioning
should occur under the same
environmental parameters (temperature,
humidity, air exchange rate, and product
loading) as those used for chamber tests.
If this is not possible, the conditioning
environmental parameters should be well
documented. Ideally, the sample should
be conditioned over its complete life
cycle up to the time of testing. If this is
not possible, conditioning should be
conducted for a period of time sufficient
to allow the emissions to equilibrate to
the test conditions (e.g., one to two
weeks).
Care should be taken in testing
materials which have been used or stored
with other materials. In such cases, the
material of interest could have acted as a
"sink" and adsorbed organics from the
other materials. Subsequent testing could
provide emissions data which represent
the re-emission of the adsorbed
compounds rather than emissions from
the original material.
Collection of a representative sample of
chamber effluent requires the use of a
sampling strategy that is appropriate to
the ranges of volatilities of the
compounds present. The information
obtained from the GC/MS headspace
analysis can be used to select
appropriate sample collection and
concentration media. As discussed
above, the sampling method can range
from syringe/pump sampling to
adsorption on various sorbent media.
Sampling techniques must also be
appropriate to the concentrations of
compounds in the chamber air stream.
When testing wet materials such as
glues, waxes, and wood finishes,
chamber concentrations may change by
orders of magnitude over a period of
minutes. Accurate description of chamber
concentration with time may require
sampling very frequently or use of a
continuous or semi-continuous monitor. A
combination of both techniques is the
most effective way to characterize rapidly
changing emissions. The concentration of
individual compounds varies as the
material ages. In some cases,
compounds not detected in the
headspace or in the first few hours of
testing may become the major emission
component. Therefore, a total
hydrocarbon monitor can be effective in
tracking rapidly changing concentrations
but may provide an incomplete qualitative
picture.
It is important, therefore, to monitor
changes in the emission profile as the
material dries. The sampling strategy
should provide a means to collect
approximately the same mass in each
sample. Thus, the sample volume is an
important consideration. When chamber
concentrations are high, sample volume
must be kept low to avoid breakthrough
in the collection trap or overloading of the
concentrator column of a purge and trap
device. Sample volumes of less than one
L can be drawn directly by gastight
syringes, then injected through a heated
port to a clean air stream flowing through
sampling cartridges. Much smaller
samples (e.g., 1 cc) can be injected
directly into the GC. Larger volume
samples are taken by pulling chamber air
stream through sample cartridges as
described above. Since the flow through
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I
the cartridges is constant, increasing the
sampling time will increase the sample
volume. It may be necessary to conduct
trial runs to develop a sampling strategy.
The analysis technique depends on the
sampling strategy and adsorbent media
employed. Methods of introducing the
sample to the GC include direct injection,
thermal desorption followed by purge and
trap concentration, and solvent extraction
followed by liquid injection.
Data Analysis
Data reduction and analysis is a
multistep process. Electronic
spreadsheets can be used to reduce and
compile the environmental and chemical
analysis data with minimal data entry
steps. Chamber concentration data are
used in various models to produce
estimates of material/product emission
rates.
Environmental and GC Data
Environmental data (i.e., temperature,
relative humidity, flow rate) can be
recorded manually or automatically
stored (e.g., on floppy disks) by a PC-
based system. GCs (including GC/MS)
are interfaced to computing integrators
(or PC-based chromatographic
dataanalysis systems) for plotting of the
chromatograms and computation of the
areas of peaks obtained. The data output
is printed on paper as an analog
chromatogram plus a summary report.
The data can also be stored on magnetic
media for future review or reprocessing.
The environmental information and the
GC analysis results are combined to give
chamber concentrations for individual
compounds and total organics. Chamber
concentration data coupled with sample
size and chamber air exchange rate are
then used to estimate emission factors.
Emission Factors
Emission factors for organics from
indoor materials are usually expressed in
terms of mass/area-time. In some cases,
emission factors are reported as
mass/mass-time, or, in the case of caulk
beads, mass/length-time. They are
calculated for individual organic
compounds, as well as for total measured
organics. The method for calculating the
emission factor depends on the type of
source being tested.
For materials with a relatively constant
emission rate over the test period, the
chamber concentration will reach and
maintain a constant equilibrium value. For
such materials the calculation of the
emission factor, when sinks are ignored,
is straightforward:
EF = C(Q/A) (1)
where, EF = Emission factor, mg/m2-hr '
C = Equilibrium chambe
concentration, mg/m3
Q = Flow through chamber
m3/hr
A = Sample area, m2
For sources that have decreasing
emission rates over the test period, .
different procedure is required. Thi
method (described in detail in the fu
report) applies to sources with initial!
high emission rates that decrease wit
time. Most "wet" sources exhibit sue
behavior. Equation 2 describes the rate c
change in emission factor as a first ord«
reaction:
R =
(2
where, R0 = Initial emission facto
mg/m2-hr
k = First order rate constant,
hr-1
t = Time, hr
It is emphasized that these methods f(
determining emission factors are m
applicable to sources that do not exhit
either constant or simple exponent)
decay emissions over time, and othi
emission models may be required.
The EPA author, Bruce A. Tichenor (also the EPA Project Officer, see below), is with Air and Energy Engineering
Research Laboratory, Research Triangle Park, NC 27711.
The complete report, entitled "Indoor Air Sources: Using Small Environmental Test Chambers to Characterize
Organic Emissions from Indoor Materials and Products," (Order No. PB 90-110 131/AS; Cost: $15.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Official Business
Penalty for Private Use $300
EPA/600/S8-89/074
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