United States Environmental
Protection Agency
Office of Research and Development
Research Triangle Park, NC 27711
EPA/600/N-97/001 Fall/Winter 1996
&EFA
Inside I A Q
EPA's Indoor Air Quality Research Update
COST ANALYSIS OF VOC AIR CLEANERS: ACTIVATED
CARBON VS. PHOTOCATALYTIC OXIDATION
Historically, gaseous air cleaners for removing volatile organic
compounds (VOCs) from indoor air have been utilized only infrequently.
In such cases, the most common technology is adsorption on granular
activated carbon (GAC). Common concerns about GAC air cleaners are:
1) they are generally not designed and operated to handle spikes in the
airborne VOC concentrations, so that they become overloaded by spikes
and may thus serve to shave the peaks rather than to actually reduce
cumulative occupant exposure; and 2) the sorbed organics remain on the
carbon, and thus still must be disposed of in some manner.
Photocatalytic oxidation (PCO) might be considered an alternative to GAC
for VOC air cleaners. PCO should destroy the organics, so that the need for
subsequent disposal would be eliminated. However, PCO is a
developmental process, with insufficient kinetic data to demonstrate its
ability to completely and economically destroy the full range of organic
compounds that can be found in the indoor environment at relatively low
concentrations, without producing organic intermediates in the off-gas.
There are no successful commercial demonstrations of PCO reactors for
this application, and only limited consideration of practical reactor designs.
To assess the economic potential of PCO, a comparison was made of the
capital and annual costs for two indoor air cleaners based on GAC vs.
PCO technology. Both air cleaners were assumed to be challenged with
a steady inlet VOC concentration of 1 ppmv.
The GAC estimates are based on one commercially available unit (see
Figure 1). Equipment and carbon replacement costs were obtained from
the manufacturer. Installation and incremental air handler costs were
derived using R. S. Means Mechanical Cost Data. Energy cost impacts
were computed using the DOE-2 building energy model. Carbon
replacement frequency (every 2 months) was estimated based upon
independent data.
The PCO estimates were based on one possible generic reactor
configuration (see Figure 2). The reactor is assumed to be a packed bed
with an enhanced titanium dioxide (TiO2) photocatalyst deposited on
suitable supports [transparent to ultraviolet (UV) radiation], irradiated
by
COMING!
July 21-23, 1997
Engineering Solutions to Indoor Air
Quality Problems Symposium
(See page 12 for announcement)
In This Issue
Page
Cost Analysis of VOC Air Cleaners:
Activated Carbon vs. Photocatalytic
Oxidation 1
Evaluation of VOC Emissions from an
Alkyd Paint 4
Glossary of Acronyms 5
Reducing Solvent and Propellant Emissions
from Consumer Products 6
Possible Role of Radon Reduction Systems
in Combustion Product Spillage 8
Summaries of Recent Publications 9
Symposium Announcement 12
Inside IAQ is distributed twice a year and
highlights indoor air quality (IAQ) research
conducted by EPA's National Risk
Management Laboratory's (NRMRL) Indoor
Environment Management Branch (IEMB). If
you would like to be added to or removed from
the mailing list, please mail, fax, or e-mail
your name and address to:
Inside IAQ
Art. Kelly Leovic (MD-54)
U.S. EPA
Research Triangle Park, NC 27711
Fax: 919-541-2157
E-mail: kleovic@engineer.aeerl.epa.gov
(Continued on Page 2)
-------
a suitable UV source. This is one of several generic reactor
designs considered in the literature. The reactor is assumed
to operate at 40 °C, necessitating the recuperative heat
exchanger configuration shown in the Figure 2.
Best-case assumptions were used for the PCO reactor
design and operation to provide what might be an optimistic
estimate of PCO costs. The reaction rate for oxidation of
the range of VOCs present in the inlet was assumed to be 4
x 106 g of catalyst per gmol/sec of VOC feed. This
represents perhaps the fastest kinetics for the most reactive
individual organic compounds reported in the literature with
effective irradiation. In practice, with the range of (probably
less reactive) organics that will be present, the kinetics
would be poorer. Also, it was assumed (based on essentially
no data) that the catalyst bed will have to be regenerated
every 4 months, and replaced every 5 years. These
assumptions are probably optimistic, especially at the
relatively low operating temperature.
The equipment and installation costs for the reactor and
other components in Figure 2 - also including the costs of
a larger air handler - were judiciously estimated using the
Means data, the W. W. Grainger Catalog, and heating,
ventilating, and air-conditioning (FfVAC) texts. Catalyst
costs were developed based upon contacts with specialty
catalyst manufacturers (including Degussa Corp., a major
TiO2 photocatalyst vendor), and are felt to be reasonably
good. System pressure drops were estimated using Perry's
Chemical Engineers' Handbook. Total building energy cost
impacts were computed using the DOE-2 model.
The results of this cost analysis are presented in Table 1, in
terms of $ (or $/year) per 1,000 ftVmin (MCFM) of air
throughput. As shown, the installed cost of the PCO system
is about 10 times that of the GAC. This due to the high
costs of the PCO reactor (about three-quarters of which is
associated with the UV-related electrical equipment), the
initial catalyst charge, the recuperative heat exchanger, and
the added ducting.
But the annual cost of the PCO system is only about 2
times that of the GAC. The difference is reduced to a factor
of 2 because the GAC carbon is assumed to have to be
replaced 6 times per year, whereas the PCO catalyst is
optimistically assumed to be replaced only once every 5
years.
(Continued on Page 3)
Table 1. Summary Cost Comparison of GAC Versus
PCO for VOC Control in Indoor Air
Cost Item
Equipment and Installation
Costs ($/MCFM)
Reactor (excluding
carbon/catalyst)
Initial carbon/catalyst charge
Duct heater and controls
Air-to-air heat exchanger
Enlarged central air handler
(increased static pressure)
Additional ducting, elbows,
dampers, etc.
TOTAL INCREMENTAL
INSTALLED COSTS
Cost ($/MCFM or
$/yr/MCFM)
Activated
Carbon
$ 530
240
~
~
40
370
$ 1,180
Photo-
catalytic
$ 3,300
3,400
600
2,600
150
2,000
$ 12,050
Total Annual Costs ($/yr/MCFM)
Operating
Electricity cost (increased
HVAC cooling load and fan
static pressure, power for
photocatalytic reactor)
Maintenance
Regeneration of catalyst
Replacement of UV bulbs
Replacement of carbon
Capital Charges
Catalyst depreciation (5 yr
straight)
Equipment depreciation (10 yr
straight)
Interest, taxes, insurance
TOTAL INCREMENTAL
ANNUAL COST
$ 50
2,170
120
70
$ 2,410
$ 1,150
650
500
750
850
750
$ 4,650
Inside IAQ, Fall/Winter 1996
Page 2
-------
Even with the optimistic assumptions used for the PCO
system, the PCO reactor configuration used here is
estimated to cost significantly more than GAC for this
application. To reduce costs, the developers of
photocatalytic processes must: 1) demonstrate improved
catalysts offering faster reaction rates and longer lifetimes
at ambient reaction temperatures; and 2) develop improved
reactor designs that provide greater exposed catalyst
surface per unit volume, improved catalyst irradiation, and
reduced pressure drop.
If PCO systems are more expensive to install and operate
than GAC systems, it is critical that commercial-scale PCO
reactors be demonstrated to reliably achieve consistently
high destruction of a wide array of organic compounds
without the appearance of intermediate oxidation products
in the off-gas. To justify the higher cost, PCO units must be
able to handle the VOC spikes that cause overloading of
GAC units. (EPA Contact: Bruce Henschel, 919-541-4112,
bhenschel@engineer.aeerl.epa.gov)
Return
Air
Carbon Filter
I
To
Air Handler
and Coils
Figure 1. Granular Activated Carbon VOC Air Cleaner
(Equipment added as part of VOC air cleaner shown with solid lines)
Reactor
(40°C)
Regeneration
Bypass Loop
Figure 2. Photocatalytic Oxidation VOC Air Cleaner
(Equipment added as part of VOC air cleaner shown with solid lines)
Inside IAQ, Fall/Winter 1996
Page 3
-------
EVALUATION OF VOC EMISSIONS FROM AN
ALKYD PAINT
Despite increased use of latex paints indoors in the past few
decades, large quantities of alkyd paints continue to be
used. Alkyd paints are of concern because they normally
contain high percentages of organic solvents. As a result,
use of alkyd paints in indoor environments may result in
exposure of building occupants to volatile organic
compounds (VOCs) emitted as the paint dries.
A primer and an alkyd semigloss paint produced by a major
U.S. paint manufacturer were selected for lEMB's current
source characterization research. The objectives of the
research include: 1) determining VOC emission rates and
patterns; 2) measuring specific emission profiles and peak
concentrations of C-9 aromatics, alkanes, and other major
VOCs emitted; 3) developing source emission models, with
emphasis on the fundamental mass transfer models; 4)
determining the effects of indoor sinks on exposure risk to
alkyd paint VOCs; 5) comparing total VOC (TVOC)
emission profiles measured in small chambers, a large
chamber, and the EPA test house; and 6) evaluating source
management options and demonstrating the effectiveness of
selected options.
Table 2 shows the volatile contents and densities of the
primer and the alkyd paint as determined by EPA Method
24, "Determination of Volatile Matter Content, Water
Content, Density, Volume of Solids, and Weight of Solids
of Surface Coatings." Table 3 shows the content of VOCs
in the test products determined by the proposed EPA
Method 311, "Analysis of Hazardous Air Pollutant
Compounds in Paints and Coatings by Direct Injection into
a Gas Chromatograph." Decane and undecane are the most
abundant components in the primer and paint, respectively,
indicating that the primer is more volatile than the paint.
For this study, small chamber tests were conducted using a
yellow pine board as the substrate to characterize VOC
emissions. The pine board was purchased locally and cut
into 16 by 16 cm pieces. The exposed edges of the board
were sealed with sodium silicate solution. The primer was
applied to one side of the board with a 10 cm paint roller,
and then the board was placed in the chamber for VOC
emission measurements. After 1.14 hours, the board was
taken out of the chamber and 2.67 g of the alkyd paint was
applied as a topcoat to the side of the board already painted
with the primer. The painted board was returned to the
chamber for additional VOC emission measurements.
The measured TVOC concentration profiles are shown in
Figure 3. A mass balance indicated that almost all the
VOCs were emitted within the 20 hour test period. The
measured TVOC concentration profiles were simulated by
using a mass transfer model developed by EPA:
dC/dt = L- k- (CV-M/M0 - C) -N-C
dM/dt = -k- (CV-M/M0 -C)
where
C = chamber concentration, mg/m3;
t = time, h;
L= loading factor (0.48), nr1;
k = mass transfer coefficient, m/h;
Cv = total concentration for TVOC, mg/m3;
M = TVOC mass remaining in the source, mg/m2;
M0 = TVOC mass applied, mg/m2; and
N = air exchange rate (0.525), h"1.
The initial condition was t =0, C = 0, and M = M0. The
value of mass transfer coefficient, k, was 6 m/h as
determined previously in the 5 3 -L chamber. The total vapor
pressure, Cv, was estimated by the following model based
on the formulation data (i.e., all identified compounds): Cv
= X(CV1 • x:). The estimated total vapor pressure was 28.2
g/m3 for the primer and 11.1 g/m3 for the paint.
10
Elapsed Time (h)
Figure 3. TVOC Concentrations Predicted by the Model
and Measured in a Small Chamber with a Primer
and Alkyd Paint on a Pine Board. (Primer
applied at time = 0. Alkyd paint applied at time
= 1.14; i.e., vertical line)
(Continued on Page 5)
Inside IAQ, Fall/Winter 1996
Page 4
-------
A comparison of the predicted chamber concentrations and
the measured concentration profiles is shown in Figure 3.
The mass transfer model predictions are in good agreement
with the experimental data. Since the model was developed
based on the assumption that the emissions were controlled
only by gas-phase mass transfer, the results in Figure 3
indicate that VOC emissions from the primer and the alkyd
paint are governed by a gas-film-diffusion-controlled and
fast evaporation-like process. This was also confirmed by
the mass balance results which indicated that almost 100%
of the VOCs were emitted within 20 hours after the
painting. (EPA Contact: John Chang, 919-541-3747,
jchang@ engineer.aeerl.epa.gov)
GLOSSAR YOFA CRONYMS
AARST-American Association of Radon Scientists
and Technicians
ASD-Active Soil Depressurization
DOT-Department of Transportation
ELA-Effective Leakage Area
GAC-Granular Activated Carbon
FfVAC-Heating, Ventilating, and Air-Conditioning
lAQ-Indoor Air Quality
lEMB-Indoor Environment Management Branch
NRMRL-National Risk Management Research
Laboratory
NTIS-National Technical Information Service
PCO-Photocatalytic Oxidation
SOG-Slab-on-Grade
TVOC-Total Volatile Organic Compound
UV-Ultraviolet
VOC-Volatile Organic Compound
Table 2. Volatile Contents and Densities of the Primer and
the Alkyd Paint Determined by EPA Method 24
Parameter
Volatile Contents, %
Density, g/cm3
Primer
33.3
1.33
Alkyd Paint
33.1
1.26
Table 3. Content of Selected VOCs Determined by EPA
Method 311
Compound
undecane
decane
dodecane
p-xylene
o-ethyltoluene
trans-decahydra-
naphthalene
nonane
propyl-
cyclohexane
methyl ethyl
ketoxime
p-ethyltoluene
ethylbenzene
1,2,4-trimethyl-
benzene
o-xylene
1,2,3-trimethyl-
benzene
1,3,5-trimethyl-
benzene
toluene
n-propylbenzene
octane
TVOC
Primer, mg/g
7.42
33.0
ND*
1.82
ND
2.55
19.4
4.34
ND
0.21
0.27
0.16
0.23
ND
ND
0.34
0.01
12.2
352
Alkyd Paint, mg/g
37
15.1
11.6
6.33
21.0
4.92
3.79
2.04
2.28
0.79
1.26
1.06
0.91
0.33
0.31
0.26
ND
ND
408
*ND= Not Detected
Inside IAQ, Fall/Winter 1996
Page 5
-------
REDUCING SOLVENT AND PROPELLANT
EMISSIONS FROM CONSUMER PRODUCTS
Consumer products typically contain an active agent, a
solvent, and a propellant. For example, hair styling products
are made up of a polymer, alcohol, and isobutane, all
contained in a precharged package. The polymer, as the active
ingredient, holds the hair strands in place. Alcohol is added for
two reasons. The first is to reduce product viscosity while it is
flowing out of the dispenser. Without the alcohol solvent, the
polymer would plug the dispenser orifice and refuse to leave
the package. The second reason for the alcohol is to reduce the
product viscosity and surface tension during the spray
formation process - a number of researchers have shown that
lower viscosity and surface tension fluids are easier to form
into the sprays desired by customers.
The propellant, isobutane, is used to force the product out of
the can and to direct it at the intended target. Isobutane, or
another hydrocarbon, is usually employed because it resides in
the can as a liquid which rapidly evaporates when the
dispenser is activated. The large volume change that occurs
when a liquid vaporizes to a gas allows only a small volume of
isobutane to be used when spraying a large volume of product.
The small volume of stored isobutane reduces package size.
To minimize indoor exposures from consumer products, the
objective of this project is to develop a mechanism for
removing the need for VOC solvents and hydrocarbon
propellents in consumer products, replacing them with water
and air, respectively. There are two barriers to be surmounted
before this goal can be achieved: product efficacy and spray
formation.
Product efficacy involves the ability of the product active
ingredient to perform its assigned task; e.g., linking strands of
hair together in the case of a hair styling product. Some active
ingredients lose their linking ability when dissolved in water.
Such concerns are best left to the product formulators.
However, when active ingredients can be dissolved in water
without losing their effectiveness, they must still be formed
into a spray. This requires the dispenser designer to overcome
the increase in both viscosity and surface tension that results
from replacing alcohol with water. In addition, the quantity of
propellant must be substantially reduced when replacing
isobutane with a more environmentally friendly gas such as
air, nitrogen, or carbon dioxide. The spray formation problem
has been the focus of this research project at Purdue
University.
The project has accomplished two things thus far: 1)
development of a dispenser (Figure 4) whose performance is
nearly independent of product viscosity and surface tension,
and 2) demonstration of markedly reduced propellant
consumption so that isobutane, or other hydrocarbon
propellants, can be replaced by an inert gas such as air,
nitrogen, or carbon dioxide. These accomplishments were
achieved through the two unique dispenser features discussed
below.
The first feature is the manner in which the product is formed
into sprays. Conventional dispensers use the "scrubbing
action" of the propellant, a process termed "aerodynamic
shear," to break up large liquid globules into much smaller
drops. Conventional aerodynamic shear is inefficient because
only a small fraction of the propellant actually contributes to
the scrubbing process. Consequently, a substantial fraction of
the propellant is wasted. In contrast, the effervescent atomizer
dispenser developed in this project intimately mixes the
product and propellant during the spray formation process,
thereby involving a much larger fraction in the scrubbing
process. As a result, there is less waste so that less propellant
needs to be stored in the package (in fact a reduction factor of
about 100, by mass, can be obtained). This reduction in
propellant consumption facilitates replacement of hydrocarbon
propellants by gases.
Brass Top
Plate f
Liquid —
Acrylic
Containment
Acrylic
Exit ^^
Orifice
1
-»•
^
•IB!
T
J
•*-
\^^
J —
BB
f V
— Liquid
^ Brass
Aerator
Tube
Air
— Injectio
Holes
Porous Insert
Figure 4. Prototype of New Spray Dispenser Developed by
Purdue University
Inside IAQ, Fall/Winter 1996
Page 6
-------
The second feature of the dispenser developed at Purdue is the
method used to prepare the product for spray formation.
Conventional dispensers (and even early effervescent
atomizers) simply routed the product to a circular exit orifice
and let the propellant do the rest. This approach worked well
as long as there was sufficient propellant available to keep the
liquid flowing around the edges of the exit orifice and gaseous
propellant down the center, an arrangement termed "annular
flow." The annular flow configuration resulted in the breakup
process proceeding through two steps: filament (or ligament)
formation and the subsequent breakup of filaments into drops.
Unfortunately, reductions in propellant consumption always
lead to the collapse of the annular flow resulting in large
chunks of liquid exiting the dispenser, producing large drops.
The Purdue research has shown that the annular flow can be
preserved at very low propellant consumption rates by
replacing the conventional circular exit orifice with a small
porous disk. These disks are commercially available and made
of sintered plastics with a wide variety of pore diameters.
The research at Purdue has demonstrated several important
advantages of ligament-controlled effervescent atomizers.
First, that products having viscosities many times that of
current consumer products can be successfully formed into
sprays. This means that these dispensers can be expected to
meet both future needs and current demands. Second, that
acceptable sprays are formed from water-based products so it
is possible to replace alcohols with water. Finally, that
propellant consumption is low enough that current package
sizes can be used without exceeding Department of
Transportation (DOT) pressurization restrictions or deceptive
packaging guidelines, while replacing hydrocarbon propellants
with air.
The design guidelines for the new dispenser will be available
in late 1997. (EPA Contact: Kelly Leovic, 919-541-7717,
kleovic@ engineer.aeerl.epa.gov)
THE INDOOR AIR QUALITY INFORMATION CLEARINGHOUSE
(IAQ INFO)
IAQ INFO is an easily accessible, central source of information on IAQ. It is supported by EPA's Office of Air and
Radiation's Indoor Environment Division.
IAQ INFO can provide information on many aspects of
IAQ:
^ Indoor air pollutants and their sources
^ Health effects of indoor air pollution
^ Testing and measuring indoor air pollution
^ Controlling indoor air pollutants
^ Constructing and maintaining homes and
commercial buildings to minimize IAQ problems
^ Existing standards and guidelines related to IAQ
^ General information on lAQ-related federal and
state legislation
You may call a toll-free number to speak to an
information specialist Monday through Friday, 9:00 a.m.
to 5:00 p.m. EST. After hours, you may leave a voice
message. You may inquire by fax or mail anytime.
IAQ INFO contains:
^ Citations and abstracts on more than 2,000 books,
reports, newsletters, and journal articles
^ An inventory of publications prepared by the
federal government, including fact sheets,
pamphlets, directories, training materials, and
reports
^ Information on more than 150 government
research, public interest, and private sector
organizations in the IAQ field
IAQ INFO
P.O. Box 37133
Washington, DC 20013-7133
1-800-438-4318
202-484-1307
Fax: 202-484-1510
Inside IAQ, Fall/Winter 1996
Page 7
-------
POSSIBLE ROLE OF RADON REDUCTION
SYSTEMSW COMBUSTION PRODUCT SPILLAGE
EPA's Radon Mitigation Standards currently require that back-
draft testing be conducted following the installation of active
soil depressurization (ASD) systems for residential reduction.
This testing is specified to ensure that the ASD system is not
causing sufficient additional depressurization of the house to
create or exacerbate spillage of combustion products from
natural draft combustion appliances.
A computational sensitivity analysis was conducted to assess
whether there are conditions where it can safely be assumed
that serious spillage will not be caused by the ASD system. If
so, it might be possible to relax the requirement for back-draft
testing under such conditions.
The parameters varied in conducting this sensitivity analysis
included: house floor area (from 100 to 280 m2); normalized
shell leakage area (0.7 to 9.0 cm2 at 4 Pa per m 2 of floor
area); the rate at which the ASD system is exhausting house
air (5 to 35 L/s); and the combined exhaust rate of appliances
other than the ASD system (50 to 140 L/s). The ranges
selected for each parameter cover typical ranges that would be
encountered in the U.S. housing stock.
The results of these computations are summarized in Tables 4
and 5, for two cases:
1) Conditions representative of the spillage test specified in
a recent standard issued by the Canadian General
Standards Board (Standard CAN/CGSB-51.71-95).
These conditions assume that a potential threat of serious
spillage exists when house depressurizations are greater
than 5 Pa with the ASD and all exhaust appliances
(except bathroom fans) operating. Results are shown in
Table 4.
2) More conservative (stringent) conditions. These conditions
assume that a potentially serious spillage threat can exist
when house depressurization reaches 3.5 Pa with all
exhausts (including bathroom fans) operating. See Table
5.
Tables 4 and 5 show the normalized house leakage areas that
would be required to avoid exceeding these depressurizations
(5 and 3.5 Pa), as a function of floor area and ASD exhaust
rate. The values assume an exhaust rate for the non-ASD
exhaust appliances (not shown in the tables), dependent on
house size.
Table 5 shows that - even with the smallest house (100 m2)
and the highest ASD exhaust flows - the ASD system would
not be predicted to create or exacerbate serious spillage, even
under conservative assumptions reflected by the table, as long
as the normalized leakage area is greater than about 4 cm2/m2.
For a reference point, one data set containing over 12,000
houses suggests that the mean leakage area for U.S. houses
might be as high as 10 cm2/m2. Thus, it would appear that
ASD systems should not create or exacerbate serious spillage
in most of the housing stock. On the other hand, Table 4
shows that - even with the largest house (280 m2) and the
lowest ASD exhaust flows - the ASD system could contribute
to spillage even under the more lenient assumptions reflected
by that table, if the normalized leakage area is less than about
2 cm2/m2. Some fraction of the U.S. housing stock does have
leakage areas below this amount, especially in colder climates.
Thus, ASD can contribute to spillage in some portion of the
housing stock.
These results indicate that, in the absence of data on the
leakiness of the house shell, it is not possible to use the house
size and ASD system flow rate to reliably estimate the risk that
an ASD installation might contribute to spillage in a given
house. Consequently, spillage testing would be needed for
essentially all ASD installations. (EPA Contact: Bruce
Henschel, 919-541-4112, bhenschel@engineer.aeerl. epa.gov)
Table 4. Maximum Allowable Depressurization=5 Pa,
Bathroom Fans Excluded (ELA=Effective Leakage
Area)
ASD exhaust out of house/
(approx. total ASD system
flow) (L/s)
0 / (0) (ASD off)
5/(10)
12 / (24)
20 / (40)
35 / (70)
Minimum ELA @ 4 Pa, per
unit floor area (cmVm2), to
ensure house depressuriza-
tion < 5 Pa for various house
floor areas
100m2
1.6
1.8
2.0
2.3
2.8
190m2
1.7
1.8
1.9
2.1
2.3
280m2
1.2
1.2
1.3
1.4
1.6
Table 5. Maximum Allowable Depressurization=3.5 Pa,
Bathroom Fans Included
ASD exhaust out of house/
(approx. total ASD flow)
(L/s)
0 / (0) (ASD off)
5/(10)
12 / (24)
20 / (40)
35 / (70)
Minimum ELA @ 4 Pa, per
unit floor area (cm2/m2), to
ensure house depressuriza-
tion < 3.5 Pa for various
house floor areas
100m2
2.9
3.1
3.4
3.7
4.4
190m2
2.6
2.7
2.9
3.1
3.4
280m2
2.1
2.1
2.2
2.4
2.6
Inside IAQ, Fall/Winter 1996
PageS
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SUMMARIES OF RECENT PUBLICATIONS
This section provides summaries of
recent publications on EPA's indoor
air research. The source of the
publication is listed after each
summary. Publications with NTIS
numbers are available (prepaid)
from the National Technical Infor-
mation Service (NTIS) at: 5285 Port
Royal Road, Springfield, VA 22161,
703-487-4650 or 800-553-6847.
A Method for Testing the Diffusion
Coefficient of Polymer Films-This
paper discusses the development and
evaluation of a method to measure the
diffusion of radon through thin polymer
films. The system was designed so that a
simple, one-dimensional transport model
could be used. The system uses radium-
bearing rock as a high level radon
source. The test film is sealed in the
system with the high concentration radon
gas on one side and an alpha detector
sealed on the other side. Three polymer
films with published values of the radon
diffusion coefficient (polyethylene,
polyester, and latex) were tested in
duplicate to evaluate the method and
determine its comparability to values in
published literature. The results show
good repeatability (10%) and some
comparability to similar published data
(20 to 200%). Source: "Proceedings of
the American Association of Radon
Scientists and Technicians' (AARST)
1996 International Radon Symposium,"
Sept. 29 - Oct. 2, 1996. (Lead Author
and EPA Contact: Richard B. Perry,
919-541-2721, rperry@engineer.aeerl.
epa.gov)
An Evaluation of Indoor Radon
Reductions Possible with the Use of
Diffusion-Resistant Flexible Con-
struction Membranes-This paper
provides a modeling assessment of the
indoor radon reductions possible through
the use of "improved" radon resistant
membranes. The evaluation considers the
application of radon resistant membranes
to slab-on-grade (SOG) construction,
source strengths, and site conditions
typical of Florida. Guidance for non-
Florida construction and site conditions
is provided. Conclusions from the paper
show: 1) Placement of an integral
impermeable flexible membrane (vapor
barrier) under SOG construction can
produce significant (lOOx) reductions in
indoor radon concentration from the no
barrier case; 2) In most cases, even for
floating SOG construction, on moder-
ately high radon potential (10 pCig"1,
226Ra) sites, currently available diffusion
resistant membranes can keep indoor
radon concentrations below 4 pCiL"1; 3)
Enhanced diffusion limiting membranes
(e.g., going from IxlO"11 to 1 x 10"13mV
1 diffusion coefficients) may become cost
effective on high radon potential sites
(e.g., sites greater than 20 pCig"1226Ra);
4) The placement of a completely intact
vapor barrier is critical to limiting radon
entry into new and existing structures
even at the well-balanced indoor/
outdoor pressure differential condition (-
2.4 Pa) used in this analysis; and 5)
Comparison of the performance of new
house evaluation study results with
model predictions indicates the potential
for enhanced radon entry limiting
performance of vapor barriers, perhaps
through enhanced placement practices.
Source: "Proceedings of the AARST
1996 International Radon Symposium,"
Sept. 29 - Oct. 2, 1996. (Lead Author
and EPA Contact: David C. Sanchez,
919-541-2979, dsanchez@engineer.
aeerl.epa. gov)
Assessment of Fungal (Penicillium
chrysogenum) Growth on ThreeHVAC
Duct Materials-This paper summarizes
experimental results evaluating the
susceptibility of three types of duct
materals: fibrous glass ductboard,
galvanized steel, and insulated flexible
duct. The results indicate that, of newly
purchased duct materials, only the
flexible duct supported moderate growth
of P. chrysogenum. No fungal growth
was detected on the fibrous glass and
galvanized steel. Wetting the clean duct
samples with sterile water did not
increase amplification of the P. chryso-
genum over levels without wetting.
Soiling the samples with dust collected
from residential heating and air-
conditioning systems enhanced the
susceptibility of all three duct materials
to fungal growth. The results suggest
that dust accumulation and/or high
humidity should be properly controlled in
any HVAC duct to prevent fungal
growth. Source: Environment Inter-
national, 22,4, 425-431, 1996. (Lead
Author and EPA Contact: John C. S.
Chang, 919-541-3747, jchang@
engineer.aeerl.epa .gov)
Characterization of Manufacturing
Processes and Emissions and Pollution
Prevention Options for the Composite
Wood Panel Industry-This report
summarizes information in the literature
on emissions from the composite wood
industry and potential pollution
prevention options. Little information
exists in the literature pertaining to
pollution prevention. Most of the
available literature focuses on ways to
reduce raw material consumption and
improve manufacturing processes.
Potential pollution prevention options
presented in this report include: conveyor
belt drying; low temperature drying; high
moisture bonding adhesives; foam
extrusion; variable glue application rate;
use of alternative fiber sources such as
agricultural fiber and recycled wood
waste; and naturally derived adhesives.
Source: EPA Report, EPA-600/R-96-
066 (NTIS PB96-183892), June 1996.
(Lead Author: Cybele Martin; EPA
Contact: Elizabeth M. Howard, 919-541-
7915, bhoward@engineer. aeerl.epa.gov)
Inside IAQ, Fall/Winter 1996
Page 9
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Description of a Method for Measuring
the Diffusion Coefficient of Thin
Films to 222Rn Using a Total Alpha
Detector-This paper describes a method
for using a total alpha detector to
measure the diffusion coefficient of a thin
film by monitoring the accumulation of
radon that penetrates the film. Results
show that a virtual steady state condition
exists in the thin film during the early
stages of accumulation that allows
reliable measurements of the diffusion
coefficient without having to wait for the
final condition of equilibrium or having
to analyze the complex transient
solutions. Source: "Proceedings of
AARST 1996 International Radon
Symposium," Sept. 29 - Oct. 2, 1996.
(Lead Author and EPA Contact: Ronald
B. Mosley, 919-541-7865, rmosley@
engineer.aeerl. epa.gov)
Development of a Radon Protection
Map for Large Buildings in Florida-
This report discusses a radon protection
map that uses soil and geologic features
to show areas of Florida that require
different levels of radon protection for
large building construction. The map
was proposed as a basis for implement-
ing radon-protective construction
standards in areas of high radon risk and
avoiding unnecessary regulations in areas
of low radon risk. Separate model
analyses estimated the effectiveness of
different building construction features.
The map was compared with over
275,000 measurements in 20,156 large
buildings. A statewide bias of only -
0.004 ±1.067 standard deviations
suggests excellent average agreement.
Observations of 306 buildings with the
greatest bias showed that, with crawl
spaces, 89% measured low and only
11% measured high. Source: EPA
Report, EPA-600/R-96-028 (NTIS
PB96-168216), March 1996. (Lead
Author: Kirk K. Nielson; EPA Contact:
David C. Sanchez, 919-541-2979,
dsanchez@engineer.aeerl .epa.gov)
Effectiveness of Radon Control
Features in New House Construction,
South Central Florida-This report gives
results of a study to evaluate the
effectiveness of two slab types
(monolithic and slab-in-stem wall) in
retarding radon entry in new houses built
in accordance with the State of Florida's
proposed radon standard for new
construction over high radon potential
soils. Fourteen houses were monitored
during their construction on sites whose
soil gas radon concentrations were
screened to be >1000 pCi/L. Slab
integrity was monitored over time, and
post-construction ventilation and radon
entry were measured in all the houses.
The houses with slab-in-stem wall
foundations exhibited more slab
cracking than those with monolithic
slabs and also had higher average radon
entry rates, radon entry velocities, and
concentration ratios. However, both slab
types proved to be effective in retarding
radon entry, especially when penetrations
were properly sealed. Source: EPA
Report, EPA-600/R-96-044 (NTIS
PB96-177761), April 1996. (Lead
Author: Charles S. Fowler; EPA
Contact: David C. Sanchez, 919-541-
2979. dsanchez@ engineer.aeerl.
epa.gov)
Indoor Environment Management
Branch-This pamphlet describes lEMB's
in-house and extramural programs. In-
house research studies are conducted on
a variety of bench-, pilot-, and full-scale
test facilities in Research Triangle Park,
NC. Test facilities include eight small
environmental chambers, a large
environmental chamber, an IAQ test
house, 24 biological static chambers, a
biological dynamic chamber, a large soil
chamber, and a pilot scale ventilation test
facility. A three-phase research approach
[chamber(s)-model-test house] forms the
core of lEMB's in-house research
program. This approach ensures that test
methods, emission factors, and
source/sink models developed are
validated in a full scale environment.
Source: EPA Report, EPA-600/F-96-
004, March 1996. (EPA Contact: John
Chang, 919-541-3747, jchang@
engineer.aeerl .epa.gov)
Large Building HVAC Simulation-This
report gives the results from a project
that established the potential for using
models to analyze radon levels in large
buildings. This was done by applying
modeling tools developed in earlier work
to analyze pressures, airflows, and
indoor radon levels in a school building
monitored by IEMB and Southern
Research Institute. Source: EPA Report,
EPA-600/R-96-116 (NTIS PB97-
104715), September 1996. (Lead
Author: Lixing Gu; EPA Contact: Marc
Y. Menetrez, 919-541-7981,
mmenetrez@ engineer.aeerl.epa.gov)
Research Agenda on Air Duct
Cleaning-Duct cleaning practices
currently include: removal of dust and
dirt from the ducts and other HVAC
system components; application of
antimicrobial agents to kill bacteria and
fungi; encapsulants and sealants to
contain imbedded contaminants; and the
introduction of ozone to mask odors and
kill microbiological organisms. All have
the potential to affect IAQ. Four priority
research areas are discussed to reduce
exposure to indoor pollutants: 1)
contaminant control techniques, 2)
application and use of antimicrobial
agents, 3) HVAC system sealants/
encapsulants, and 4) use of ozone in
ventilation systems. Source: Accepted for
publication in Indoor Air. (Lead Author:
Marie S. O'Neill; EPA Contact: R. N.
Kulp, 919-541-7980,
rkulp@engineer.aeerl.epa.gov)
Inside IAQ, Fall/Winter 1996
Page 10
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Site-specific Protocol for Measuring
Soil Radon Potentials for Florida
Houses-This report describes a protocol
for site-specific measurement of radon
potentials for Florida houses that is
consistent with existing residential radon
protection maps. The protocol gives
further guidance on the possible need for
radon-protective house construction
features. Sensitivity analyses identified
radium concentration, soil layer depth,
soil density, soil texture, and water table
depth as the independent parameters
dominating indoor radon. Radium
concentration and water table depth were
most important. Soils up to 2.4 m deep
contributed to indoor radon in uniform-
radium scenarios, and soil layers about
0.6 m thick significantly affected radon
in cases of non-uniform radium
distributions. Source: EPA Report, EPA-
600/R-96-045 (NTIS PB96-175260),
April 1996. (Lead Author: Kirk K.
Nielson; EPA Contact, David C.
Sanchez, 919-541-2979,
dsanchez@engineer.aeerl .epa.gov)
Sources and Factors Affecting Indoor
Emissions from Engineered Wood
Products: Summary and Evaluation of
Current Literature-Engineered wood
components (e.g., particleboard and
medium-density fiberboard) are common
to several types of consumer wood
products (e.g., residential and ready-to-
assemble furniture and kitchen cabinets).
The resins used to bind the wood, the
wood itself, coatings, and laminates
applied to the components all affect
emissions of formaldehyde and other
VOCs from the products to the indoor
environment. This report evaluates
existing data and testing methodologies.
Information in the report was used to
select engineered wood components with
various finishing and resin systems for a
cooperative research project between
IEMB, Research Triangle Institute, and
industry. The research objectives are to
characterize indoor air emissions from
engineered wood products and to
identify and evaluate pollution
prevention approaches for reducing
indoor air emissions from these
products. Source: EPA Report, EPA-
600/R-96-067 (NTIS PB96-183876),
June 1996. (Lead Author: Sonji Turner;
EPA Contact: Elizabeth M. Howard,
919-541-7915, bhoward@engineer
.aeerl.epa.gov)
Technical Basis for a Candidate
Building Materials Radium Standard-
This report summarizes the technical
basis for a candidate building materials
radium standard. It contains the standard
and a summary of the technical basis for
the standard. Source: EPA Report, EPA-
600/R-96-022 (NTIS PB96-157565),
March 1996. (Lead Author: Vern C.
Rogers; EPA Contact: David C.
Sanchez, 919-541-2979,
dsanchez@engineer.aeerl .epa.gov)
Inside IAQ, Fall/Winter 1996
Page 11
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SYMPOSIUM ANNOUNCEMENT
Engineering Solutions to Indoor Air Quality Problems
The second biennial Engineering Solutions to Indoor Air Quality Problems Symposium, an international symposium
cosponsored by EPA's National Risk Management Research Laboratory and the Air & Waste Management Association, will
be held July 21-23,1997, at the Sheraton Imperial Hotel and Conference Center in Research Triangle Park, NC.
Topics will include:
! Managing the Risk of Indoor Air Pollution ! Ventilation for Indoor Air Quality
! Indoor Air Source Characterization Methods ! HVAC Systems as Sources of
! Indoor Air Source Management Indoor Air Pollution
! Low Emitting/Low Impact Materials Development ! Air Duct Cleaning
(Pollution Prevention) ! Particles in Indoor Air
! Biocontaminant Prevention and Control ! Indoor Air Quality Modeling
! Indoor Air Cleaning Methods ! Costs of Managing Indoor Air Quality
For registration information, please contact the Registrar, Air & Waste Management Association, phone: (412) 232-3445 or
(412) 232-3444 ext. 3142.
For information on exhibition opportunities, please contact David Randall, phone: (919) 677-0249, ext. 5139# or fax: (919)
677-0065.
United States
Environmental Protection Agency
Indoor Environment Management Branch _ p.
MD-54
Research Tnangle Park, NC 27711 PERMIT Na
FIRST CLASS MAIL
POSTAGE AND FEES PAID
Official Business
Penalty for Private Use
$300
EPA/600/N-97/001, Fall/Winter 1996
An Equal Opportunity Employer
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