United States Environmental Office of Research and Development

Protection Agency Research Triangle Park, NC 27711

EPA/600/N-97/001 Fall/Winter 1996

 EPA Inside IAQ 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 

(Continued on Page 2)

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

 Att. Kelly Leovic (MD-54)

 U.S. EPA

 Research Triangle Park, NC 27711

 Fax: 919-541-2157

 E-mail: kleovic@engineer.aeerl.epa.gov
Inside IAQ, Fall/Winter 1996 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 40EC, 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 (HVAC) 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 ft3/min (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 ($/MCFM or

$/yr/MCFM)

Cost Item

Equipment and Installation

Costs ($/MCFM)

Activated

Carbon

Photocatalytic

Reactor (excluding

carbon/catalyst)

$ 530 $ 3,300 

Initial carbon/catalyst charge 240 3,400 

Duct heater and controls -- 600 

Air-to-air heat exchanger -- 2,600 

Enlarged central air handler

(increased static pressure) 40 150 

Additional ducting, elbows,

dampers, etc. 370 2,000 

TOTAL INCREMENTAL

INSTALLED COSTS $ 1,180 $ 12,050 

Total Annual Costs ($/yr/MCFM)

Operating

Electricity cost (increased

HVAC cooling load and fan

static pressure, power for

photocatalytic reactor) $ 50 $ 1,150

Maintenance

Regeneration of catalyst

Replacement of UV bulbs

Replacement of carbon

-- 

-- 

2,170 

650 

500 

-- 

Capital Charges

Catalyst depreciation (5 yr

straight)

Equipment depreciation (10 yr

straight)

Interest, taxes, insurance

-- 

120 

70 

750 

850 

750 

TOTAL INCREMENTAL

ANNUAL COST $ 2,410 $ 4,650 
Inside IAQ, Fall/Winter 1996 Page 3

Return

Air

To

Air Handler

and Coils

Carbon Filter

Return Air

(25°C)

 Heat 

Exchanger

Reactor

(40°C)

Regeneration

Bypass Loop

Heater

To Air

Handler

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)

Figure 1. Granular Activated Carbon VOC Air Cleaner

(Equipment added as part of VOC air cleaner shown with solid lines)

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 4

0 5 10 15 20

0

2000

4000

6000

8000

10000

12000

Elapsed Time (h)

Concentration (mg/m3)

Data Model

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 IEMB'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/Mo - C) -N@C

dM/dt = -k@ (Cv@M/Mo -C) 

where

C = chamber concentration, mg/m3;

t = time, h;

L= loading factor (0.48), m-1;

k = mass transfer coefficient, m/h;

Cv = total concentration for TVOC, mg/m3;

M = TVOC mass remaining in the source, mg/m2;

Mo = TVOC mass applied, mg/m2; and

N = air exchange rate (0.525), h-1.

The initial condition was t =0, C = 0, and M = Mo. The

value of mass transfer coefficient, k, was 6 m/h as

determined previously in the 53-L chamber. The total vapor

pressure, Cv, was estimated by the following model based

on the formulation data (i.e., all identified compounds): Cv

= 3(Cvi @ x I). The estimated total vapor pressure was 28.2

g/m3 for the primer and 11.1 g/m3 for the paint.

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 5

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) 

GLOSSARY OF ACRONYMS

AARST-American Association of Radon Scientists

and Technicians

ASD-Active Soil Depressurization

DOT-Department of Transportation

ELA-Effective Leakage Area

GAC-Granular Activated Carbon

HVAC-Heating, Ventilating, and Air-Conditioning

IAQ-Indoor Air Quality

IEMB-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 Primer Alkyd Paint

Volatile Contents, % 33.3 33.1

Density, g/cm31.33 1.26

Table 3. Content of Selected VOCs Determined by EPA

Method 311

Compound Primer, mg/g Alkyd Paint, mg/g

undecane 7.42 37

decane 33.0 15.1

dodecane ND* 11.6

p-xylene 1.82 6.33

o-ethyltoluene ND 21.0

trans-decahydranaphthalene2.55 4.92

nonane 19.4 3.79

propylcyclohexane4.34 2.04 

methyl ethyl

ketoxime 

ND 2.28

p-ethyltoluene 0.21 0.79

ethylbenzene 0.27 1.26

1,2,4-trimethylbenzene0.16 1.06

o-xylene 0.23 0.91

1,2,3-trimethylbenzeneND 0.33

1,3,5-trimethylbenzeneND 0.31

toluene 0.34 0.26

n-propylbenzene 0.01 ND

octane 12.2 ND

TVOC 352 408

* ND = Not Detected
Inside IAQ, Fall/Winter 1996 Page 6

Porous Insert

Air

Injection

Holes

Brass

Aerator

Tube

Liquid Liquid

Acrylic

Exit

Orifice

Acrylic

Containment

Tube

Brass Top

Plate

Air

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.

Figure 4. Prototype of New Spray Dispenser Developed by

Purdue University
Inside IAQ, Fall/Winter 1996 Page 7

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:

ó Indoor air pollutants and their sources

ó Health effects of indoor air pollution

ó Testing and measuring indoor air pollution

ó Controlling indoor air pollutants

ó Constructing and maintaining homes and

commercial buildings to minimize IAQ problems

ó Existing standards and guidelines related to IAQ

ó General information on IAQ-related federal and

state legislation

IAQ INFO contains:

ó Citations and abstracts on more than 2,000 books,

reports, newsletters, and journal articles

ó An inventory of publications prepared by the

federal government, including fact sheets,

pamphlets, directories, training materials, and

reports

ó Information on more than 150 government

research, public interest, and private sector

organizations in the IAQ field

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 1-800-438-4318

P.O. Box 37133 202-484-1307

Washington, DC 20013-7133 Fax: 202-484-1510
Inside IAQ, Fall/Winter 1996 Page 8

POSSIBLE ROLE OF RADON REDUCTION

SYSTEMS IN COMBUSTION PRODUCT SPILLAGE

EPA's Radon Mitigation Standards currently require that backdraft 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)

Minimum ELA @ 4 Pa, per

unit floor area (cm2/m2), to

ensure house depressurization < 5 Pa for various house

floor areas

100 m2190 m2280 m2

0 / (0) (ASD off) 1.6 1.7 1.2

5 / (10) 1.8 1.8 1.2

12 / (24) 2.0 1.9 1.3

20 / (40) 2.3 2.1 1.4

35 / (70) 2.8 2.3 1.6

Table 5. Maximum Allowable Depressurization=3.5 Pa,

Bathroom Fans Included

ASD exhaust out of house/

(approx. total ASD flow) 

(L/s)

Minimum ELA @ 4 Pa, per

unit floor area (cm2/m2), to

ensure house depressurization < 3.5 Pa for various

house floor areas

100 m2190 m2280 m2

0 / (0) (ASD off) 2.9 2.6 2.1

5 / (10) 3.1 2.7 2.1

12 / (24) 3.4 2.9 2.2

20 / (40) 3.7 3.1 2.4

35 / (70) 4.4 3.4 2.6
Inside IAQ, Fall/Winter 1996 Page 9

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 Information Service (NTIS) at: 5285 Port

Royal Road, Springfield, VA 22161,

703-487-4650 or 800-553-6847.

SUMMARIES OF RECENT PUBLICATIONS

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 radiumbearing 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 Construction 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 nonFlorida 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 (100x) reductions in

indoor radon concentration from the no

barrier case; 2) In most cases, even for

floating SOG construction, on moderately 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 1x10-11 to 1 x 10-13m

2

s

-

1

 diffusion coefficients) may become cost

effective on high radon potential sites

(e.g., sites greater than 20 pCig-1 226Ra);

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 Three HVAC

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. chrysogenum over levels without wetting.

Soiling the samples with dust collected

from residential heating and airconditioning 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 International, 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 10

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 FloridaThis 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 implementing 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 IEMB's

in-house and extramural programs. Inhouse 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 IEMB'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 11

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 uniformradium scenarios, and soil layers about

0.6 m thick significantly affected radon

in cases of non-uniform radium

distributions. Source: EPA Report, EPA600/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-toassemble 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, EPA600/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 StandardThis 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, EPA600/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)
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

! Indoor Air Source Characterization Methods

! Indoor Air Source Management

! Low Emitting/Low Impact Materials Development

(Pollution Prevention)

! Biocontaminant Prevention and Control

! Indoor Air Cleaning Methods

! Ventilation for Indoor Air Quality

! HVAC Systems as Sources of

Indoor Air Pollution

! Air Duct Cleaning

! Particles in Indoor Air

! Indoor Air Quality Modeling

! 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

MD-54

Research Triangle Park, NC 27711

Official Business

Penalty for Private Use

$300

EPA/600/N-97/001, Fall/Winter 1996

An Equal Opportunity Employer

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POSTAGE AND FEES PAID

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