Inside IAQ, Spring/Summer 2001 Page 1

We are pleased to be able to resume semiannual

publicationofInside IAQ after anunavoidable 2-year

suspension. Thisissue is being distributed via first class

mail using our most recent mailing list; in addition,

copies of this and previous editions of the newsletter

are available on the internet at:

www.epa.gov/appcdwww/crb/iemb/insideiaq.htm

United States Environmental Office of Research and Development

Protection Agency Research Triangle Park, NC 27711

EPA/600/N-01/002 Spring/Summer 2001 

 EPA Inside IAQ

EPA's Indoor Air Quality Research Update

In This Issue Page

Testing Demonstrates that Nominally Identical 

Photocopier Toners Can Have Significantly Different 

VOC Emissions .............................. 1

Identification of Hazardous Air Pollutants

 Emitted from a Shower Curtain ................. 3

A Pilot Home Asthma Intervention Study

 In Boston Public Housing ..................... 3

Candle Burning as a Potential Source of

 Indoor Air Pollution .......................... 5

The Impact of Ozone on Indoor Air Quality ......... 5

TESTING DEMONSTRATES THAT NOMINALLY IDENTICAL PHOTOCOPIER TONERS CAN HAVE

SIGNIFICANTLY DIFFERENT VOC EMISSIONS

A laboratory study has been completed on a series of

nominally identical toners, manufactured for use in a specific

dry-process photocopier. The objective was to determine the

extent to which the emissions of volatile organic compounds

(VOCs) from a given toner might be reduced through

judicious selection of the process and the polymer feedstock

used in the manufacture of that toner.

A cooperating toner manufacturer produced four nominally

identical batches of toner for a selected copier, according to

a 2x2 matrix: using two different manufacturing processes

(vented and unvented extrusion); and using two different lots

of polymer feedstock, to be fed to the extruder. The

manufacturer also provided samples of the two unprocessed

feedstocks. In addition to these manufacturer samples, toner

cartridges for this same copier were purchased from two

local retailers, representing three different toner lots. The

manufacturer, manufacturing process, and feedstock

characteristics for these retailer toners were unknown.

These toners were tested using a flow-through thermal

desorption test method, developed for this project. In this

method, toner samples were ballistically heated to the

temperature range of the copier (180 to 200 oC), and the

VOCs driven off were captured on Tenax®sorbent. These

Tenax®cartridges were then desorbed and analyzed using

gas chromatography (GC) with a flame ionization detector

(FID), calibrated for up to 21 selected individual VOCs.

Statistical analysis of the results from the manufacturer

samples showed that (p < 0.05):

• The manufacturing process (vented vs. unvented

extrusion) had no effect on toner emissions in this

study. That is almost certanly because only a

negligible vacuum (2 Pa below atmospheric) was

applied in producing the vented toners available for

this study; a vacuum perhaps 4 orders of magnitude

greater would have been required for effective

removal of VOCs.
Inside IAQ, Spring/Summer 2001 Page 2

• The feedstock had little or no effect on the emissions

from the toners because there was no difference in

the emissions between the two feedstocks used in

this study.

• Each unprocessed feedstock generally has 15 to

30% higher emissions of ethylbenzene, p-xylene, and

styrene, compared to the toners manufactured using

that feedstock. This observation would be consistent

with the thesis that some fraction of these

compounds – present as impurities in the feedstock

– is driven off during the extrusion process.

• Each unprocessed feedstock consistently has about

30 to 60% lower emissions of benzaldehyde and

acetophenone, compared to the toners manufactured

using that feedstock. These observations would be

consistent with the thesis that some amount of these

oxygenated compounds is created by thermaloxidative degradation of the polymer during the

extrusion process.

Statistical analysis of the results from the retailer toners

showed that (p < 0.05):

• All of the retailer toners have emissions of

ethylbenzene, xylenes, styrene, and acetophenone

that are significantly lower (by 15 to 100%) than

those from the manufacturer toners (with either

feedstock).

• All of the retailer toners have emissions of

benzaldehyde that are significantly higher (by 125 to

350%) than those from the manufacturer toners.

• In general, the total VOC (TVOC) emissions from

the retailer toners are statistically the same as those

from the manufacturer toners, even though the

emissions of individual compounds can vary

significantly.

• In general, there is no statistical difference in

emissions between the retailer toners, within the

statistical power of this analysis (two samples per

toner).

Overall, the conclusions from this study are:

1. From comparison of the manufacturer and retailer

toners tested here, it is clear that nominally identical toners –

manufactured to meet the fuser specifications for a single

photocopier – can have significantly different emissions of

individual VOCs when heated in the laboratory. Emissions

of a given compound can vary by a factor of 2 or more

between toners.

2. Even significant differences in emissions of individual

VOCs between toners might not indicate one as a clearly

preferable low-emitting product. Comparison of the

manufacturer and retailer toners indicates that – while the

retailer toners had much lower emissions of some

compounds (ethylbenzene, xylenes, styrene, acetophenone)

– they had higher emissions of other compounds

(benzaldehyde, phenol). (All of these compounds, except

benzaldehyde, are Hazardous Air Pollutants.) The

difference in TVOC emissions between the two toner sets is

modest at best, and often not statistically significant.

3. The differences in emissions between the

manufacturer and retailer toners are almost certainly due to

differences between the manufacturing processes and/or the

feedstock polymers used in the two cases. But without

information on the retailer process(es) and feedstocks, the

specific factors creating the differences could not be

identified in this study.

4. Because the specific factors creating the emission

differences between the manufacturer and retailer toners

cannot be identified, it is not possible from this study to make

specific recommendations regarding how process or

feedstock might be modified in order to produce loweremitting toners for a given copier.

5. The tests on the manufacturer toners showed that

vented extrusion did not produce toners having lower

emissions than did unvented extrusion; but this result was

almost certainly obtained because only a negligible vacuum

(2 Pa) was applied during vented extrusion. These tests also

showed that the feedstock had only modest, if any, impact

on toner emissions; but the feedstocks were almost identical,

creating this result.

6. The tests on the manufacturer toners and feedstocks

demonstrated that essentially all of the compounds observed

in the toner emissions result, at least in part, from impurities

that are present in the feedstocks to begin with. The tests

also demonstrated that the concentrations of some species

can be increased during the extrusion process, presumably by

oxidative degradation of the polymer. These observations

can be used to postulate explanations for the differences in

emissions between the manufacturer and retailer toners.

(EPA Contact: Bruce Henschel, 919-541-4112,

henschel.bruce@epa.gov)
Inside IAQ, Spring/Summer 2001 Page 3

IDENTIFICATION OF HAZARDOUS AIR POLLUTANTS EMITTED FROM A SHOWER CURTAIN

A single soft vinylshower curtain was tested. The 70 by 72–

inch shower curtain was 100% vinyl, manufactured in China

for a large U.S. retailer. The product was purchased at a

local retail outlet. The shower curtain was colored, primarily

blue. It had a strong “plastic” odor when removed from the

package. 

Equilibrium headspace was analyzed using a newly

developed static chamber test method. The test was

performed by placing samples of the shower curtain in a 53-

L stainless steel chamber. After loading the shower curtain

samples, the chamber was sealed and placed in an incubator

set at 23oC. The tests were static with no air flow to the

chamber. Special racks were constructed to suspend the

shower curtain in the chamber to maximize the exposed

surface area and accelerate the experiments. The racks

consist of a frame with stainless steel bars on the top and

bottom spaced approximately 2 cm apart. The shower

curtain was cut into strips with nominal width of 34.3 cm and

the strips were woven through the bars.

Headspace chamber air samples were collected on Tenax

sorbent tubes using a sampling pump. The samples were

analyzed by thermal desorption interfaced to a gas

chromatograph equipped with a flame ionization detector. 

Figure 1 is a chromatogram of the headspace sample taken

at the 168th h. Among the 14 compounds identified, methyl

alcohol (methanol), methylene chloride, toluene, and phenol

were classified as hazardous air pollutants by the 1990 Clean

Air Act Amendments. (EPA Contact: John Chang, 919-541-

3747, chang.john@epa.gov)

Figure 1. Chromatogram identifying hazardous

compounds.

A PILOT HOME ASTHMA INTERVENTION STUDY IN BOSTON PUBLIC HOUSING

A small study was recently completed to investigate the

feasibility of implementing asthmagen reduction measures in

Boston Public Housing. The study is a community/

university/government collaboration between the Tufts

University School of Medicine, the Harvard University

School of Public Health, the Committee for Boston Public

Housing, the Tenant Task Force of the Franklin Hill Housing

Development (Figure 2), Boston Medical Center, and the

U.S. Environmental Protection Agency’s Office of Research

and Development and Region 1. The goal of the program

was to reduce household environmental fac tors, such as

allergens, airborne particles, and irritant gases, that contribute

to the exacerbation of asthma symptoms. The program was

designed to carry out interventions in a manner that

maximized participation from both community organizations

and individual tenants involved in the study. This was a pilotscale study, intended primarily to gain experience working in

the public housing arena in order to develop hypotheses and

methods for future research projects.

Nine families with asthmatic children living in Franklin Hill

Housing Development in Boston were enrolled in the asthma

intervention program. At the beginning of the study, the

asthmatic children were evaluated by a pediatric

pulmonologist. The evaluation included administration of a

symptom frequency questionnaire, review of medication use,

and physical examination. A computerized

pneumotachometer (MultiSpiro) was used to perform

pulmonary function testing on all children over 4 years of

age. Allergy skin testing was performed for cat, mouse, dog,

cockroach, and dust mite antigens. Over the course of the

study, the participants kept a diary of asthma symptoms and

medication use.

Asthmagen-reduction Interventions

Interventions started with thorough cleaning of the

apartments and furniture, using a machine that applied an

atomized water-based solution at 200 psi, which was

extracted to leave little moisture in fabric, upholstery, and
Inside IAQ, Spring/Summer 2001 Page 4

Figure 2. Franklin Hill Apartments

carpeting. In addition, cracks and crevices that might allow

pest entry were sealed, and pest repellant devices were

installed in some apartments. In many cases, exposed steam

piping was present, resulting in high indoor temperatures and

burn hazards. This was insulated. Mattresses and pillows on

the children’s beds, and any other beds the children slept on,

were encased in dust-mite-proof covers. Some tenants were

provided with high-efficiency particulate air (HEPA)-filtered

vacuum cleaners for their own use. Some apartments were

equipped with air filtration systems: electrostatic filters,

HEPA filters, or a modified clean-room system containing a

HEPA filter and an ozone lamp, followed by an activated

charcoal filter. The filter systems were maintained by

project staff. The specific intervention used for each

apartment was tailored to

the conditions in that

apartment.

Data Collection

In-depth qualitative and

quantitative information

was collected from these

nine apartments and their

residents. The qualitative

information included

asthma symptom diaries

and resident responses in

focus group discussions

both before and after the

interventions were

implemented. This

provided valuable insight

into the institutional, social,

economic, and personal factors that affect the use of asthma

prevention interventions in public housing. Quantitative data,

from intensive environmental monitoring, was collected to

thoroughly characterize the state of the nine public housing

apartments, and to cull hypotheses about the effectiveness of

the interventions. 

Monthly monitoring visits were made to each apartment.

During these visits, the study team made a visual inspection

for mold, wetness, cockroaches, rodent droppings, etc.

Temperature and relative humidity were measured. Inhalable

and respirable particulate matter–with aerodynamic

diameters of < 10 ?m (PM10) and < 2.5 ?m (PM2.5),

respectively– were collected on 37 mm Teflon 2 ?m-pore

filters. Twenty- four hour, time-integrated passive nitrogen

dioxide (NO2) samples were taken using Yanagisawa

Badges and analyzed by light spectrometry. Twenty-four

hour VOC samples were collected passively on thermal

desorption tubes packed with Carbotrap B, and analyzed by

gas chromatography/mass spectroscopy (GC/MS).

Dust samples were collected on cellulose extraction thimbles

(Whatman Inc., Hillsboro, OR) using a small, portable

vacuum cleaner (Eureka Mighty Mite). Composite samples

were taken from asthmatic children’s bedrooms by

vacuuming the children’s bedding and the carpeting around

the beds . These were analyzed for dust mite antigens, Der

p 1 and Der f 1; cat antigen, Fel d 1; dog antigen, Can f 1;

fungi; and endotoxin.

Other samples were

collected from the seats

and carpeting of the

apartments’ main living

areas, and analyzed for

dust mite antigens, Der

p 1 and Der f 1; cat

antigen, Fel d 1; fungi;

and dog antigen, Can f

1. A third set of

samples was collected

from kitchen cabinets

and analyzed for rodent

antigen, Mus m 1; and

cockroach antigen, Bla

g 1. Dust was also

analyzed for viable

fungus by plating onto

malt extract agar. Endotoxin, and dust mite, cat, dog, roach,

and mouse antigens were measured using a

spectrophotometric Enzyme-Linked-Immunosorbent-Assay

(ELISA) method.

Current Progress

Initial results and recommendations from this study were

presented at the Engineering Solutions to Indoor air Quality

Symposium held July 17-19, 2000, in Raleigh, North Carolina.

The conference was sponsored jointly by the Air & Waste

Management Association and the U.S. EPA. The research

was completed in the autumn of 2000, and final articles are

being prepared for submission to peer reviewed journals

(EPA Contact: Betsy Howard, 919-541-7915,

howard.betsy@epa.gov)
Inside IAQ, Spring/Summer 2001 Page 5

CANDLE BURNING AS A POTENTIAL SOURCE OF INDOOR AIR POLLUTION

Candle burning has been associated with human living

conditions for at least 1,000 years. Although no longer

primarily a means of lighting, candles are still popular in

households and certain public places, mainly for creating a

unique atmosphere. Candle sales in the United States keep

growing – about 10 to 15% per year in the last 10 years.

Industry estimates put 1999 sales at $1.3 billion for scented

candles and up to $2.3 billion for all candles. 

A special issue that has drawn some attention recently is the

lead emissions from lead-wick candles. According to the

National Candle Association, most U.S. manufacturers have

ceased lead-wick production, but some imported candles on

the market still contain lead in their wicks. EPA bought 100

sets of candles that appeared to contain metal-cored wicks.

Eight sets had lead wicks with lead contents ranging from 51

to 74%. While burning, they emitted lead at a rate from 100

to 1400 ?g/hour. Under certain indoor conditions, burning

these candles may result in lead concentrations above EPA

recommended thresholds. Furthermore, inhalation exposure

is not the only pathway for lead intake. Unlike gaseous air

pollutants, particle-bound lead tends to settle on interior

surfaces, where young children can be exposed to lead dust

through skin contact. The U.S. Consumer Product Safety

Commission is currently in the process banning the sales of

lead-wick candles in the United States.

Another issue associated with candle burning is the emissions

of fine particulate matter (PM). Although all candles

generate carbon particles during the burning process,

a well-designed and well-maintained candle emits negligible

fine PM because almost all the particles are consumed by

the flame. In fact, it is the combustion of the carbon

particles that gives the flame its bright golden color. This

process was artfully described by Michael Faraday in1861 in

his famous book The Chemical History of a Candle. On

the other hand, several factors (e.g., candle composition and

design, wick length, and drafty air) may result in imperfect

combustion. A smoldering candle could cause an indoor fine

PM concentration higher than permitted by the ambient air

quality standards. Heavy and frequent candle burning in

homes may be a contributing factor to soot deposition on

interior surfaces, causing blackened walls, ceilings, and

carpets. The exact mechanism of this phenomenon is not

well understood, however. 

Protecting the public from these potential indoor pollution

problems requires a joint effort by the industry, the public,

and governments. Some manufacturers are developing lowemission candles. Product labeling may help consumers

identify cleaner products and learn how to use them. To

some extent, burning candles is an art, and proper use of this

product can reduce emissions. Thus, public education is a

cost-effective way to deal with this kind of product. We

observed that blowing out candles could instantly produce a

large amount of particles. Some simple measures -- using a

wet cloth, candle scissors, or snuffer – could greatly reduce

such emissions. Emissions from candles vary from product

to product and from time to time. To obtain representative

emissions data, there is a need to develop standard methods

for testing. (EPA Contact: Zhishi Guo, 919-541-0185,

guo.zhishi@epa.gov)

THE IMPACT OF OZONE ON INDOOR AIR QUALITY

EPA’s Indoor Environment Mangement Branch (IEMB) is

conducting experiments to characterize the impact of ozone

on indoor air quality (IAQ). The goal of this research is to

improve our understanding of the relationship between ozone

and risk in indoor environments. Ozone is transported

indoors from ambient air and may be generated indoors by a

variety of sources including office equipment and consumer

appliances. Consumer appliances marketed as air cleaners

that intentionally produce ozone are of particular interest

because of their potential to create high ozone concentrations

and because they are advertised to improve IAQ by reacting

objectionable or odor causing volatile organic compounds 

 (VOCs) with ozone. The immediate focus of our work is to

characterize sources of ozone in indoor environments and

determine how ozone affects VOC and particle

concentrations in indoor air.

Little data are available that may be used to model and

predict the impact of ozone on IAQ. To fill this gap, we have

characterized ozone and oxides of nitrogen (NOx) emission

rates from selected consumer appliances under controlled

conditions in a room-sized environmental chamber and

evaluated their performance in our research test house.

These tests include limited evaluation of a feedback control
Inside IAQ, Spring/Summer 2001 Page 6

system designed to maintain in-room ozone

concentrations at or below 50 parts per billion

(ppb). 

We are currently investigating the impact of

operating an ozone generator air cleaner on VOC

concentrations in the controlled environment of the

test chamber. The objectives of these tests are to

identify reaction products and determine if

reactions proceed at rates that are consistent with

reaction rate constants that have been determined

for the troposphere. The reason for this objective

is obvious: ozone reacts too slowly with most

VOCs to have much impact on indoor air

concentrations – emission rates from the source(s)

and air exchange rates generally govern

concentrations. However, if an ozone generator

produces other radicals such as hydroxyls (

-OH)

that react with VOCs much more quickly than

ozone, then operation of the device may actually

alter indoor air concentrations of some VOCs.

Whether or not this improves indoor air quality is

another matter. Some of our current research

findings are presented below.

Characterization of Ozone Generator Air

Cleaner Appliances

Emissions characterization tests were conducted

in the room sized environmental chamber (see

Figure 3) to determine how much ozone and NOx

these devices generate and what factors influence

generation rate.

Ozone emission rates for a widely marketed

appliance were determined at various dial set

points (in ft2 of floor treatment area) at 50% RH

in the room-sized environmental chamber and are

shown in Figure 4. We found that ozone

generation rates (<1 to >150 mg/h) were generally

consistent with the rates stated by the

manufacturers, although the relationship between

dial setting of the ozone generator and ozone

emission rate was not linear across the range of

the dial. 

The chamber tests also revealed that ozone

generation rates decreased as relative humidity

increased for all appliances tested. As may be

seen in Figure 5, the rate of decrease was greatest

for the appliance with the highest ozone generation

rate.

Figure 3. Characterizing ozone emission rates in EPA’s roomsized test chamber.

Clean Air In

Exhaust

Fan

S F 6

Input

Chamber Exhaust

N O x Monitor Ozone Monitor

Chamber Inlet

Air Ozone Monitor

Ozone Monitor

at Air Cleaner Inlet

Figure 4. Ozone emission rates at generator set points

determined for an ozone generator air cleaner. 

0

20

40

60

80

100

120

140

160

0 200 400 600 800 1000 1200 1400 1600

Generator set point (ft2)

Ozone emission rate (mg/h)

2 Large Plates 1 Large Plate 1 Small Plate

NOx[as nitrogen dioxide (NO2)] is generated by silent discharge ozone

generators. As shown in Figure 6, NOx emission rates, determined at

50% RH, varied between appliances from different manufacturers and

ranged from 6 to 16 % mg/h of the ozone emission rate. 

Performance of the Ozone Generator Appliance in the Research

Test House

A series of tests in the research test house investigated our ability to

predict indoor ozone concentrations from chamber derived emission

rates, and investigated the performance of a sensor-feedback control

system designed to maintain ozone concentrations at or below 50 ppb.
Inside IAQ, Spring/Summer 2001 Page 7

y = -1.9525x + 247.33

R

2

 = 0.9978

y = -0.7563x + 114.23

R

2

 = 0.9863

y = -0.2317x + 45.415

R

2

 = 0.9446

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80

Chamber RH (%)

Ozone Emission Rate

 (mg/h)

M1, Model A M1, Model B M2, Model B

0.00

2.00

4.00

6.00

8.00

10.00

12.00

0 20 40 60 8 0 100 120 140 160 180

Ozone Emission Rate (mg/h)

NOx Emission Rate (mg/h) 

M1, Model A M1, Model B M2, Model A

M2, Model B Regression All M1 Regression All M2

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 2 5

Elapsed Time (h)

Ozone Concentration (ppb)

Ozone in Den Ozone Outdoors

We determined the ozone deposition velocity in the

house, determined the penetration factor for

ambient ozone, and used the IAQ model RISK to

predict the time history of ozone in the house

during operation of an ozone generator air cleaner.

We found that steady state predictions were

generally good (e.g., within ± 15% of observed)

though the model did not always represent the

concentration/time history as well. We also

observed that in-room ozone concentrations stayed

at or below 50 ppb when the generators were

operated with the controller activated (see Figure

7). The tests of the ozone generator air cleaner

with the sensor-controller activated were of 14 to

24 hr duration. Thus, these tests do not

characterize long-term performance or effects of

environmental variables on sensor-controller

performance. 

We are in the process of evaluating data from

tests conducted to investigate the impact of the

ozone generator on concentrations of VOCs in the

environmental test chamber. Preliminary tests

with styrene and limonene, common indoor air

contaminants, suggest that the effect that the

ozone generator has on IAQ can be predicted

from ozone/VOC reaction rate constants published

by atmospheric researchers over the past 30

years. Reaction products for the styrene/ozone

tests are primarily benzaldehyde and

formaldehyde.

To summarize what we have learned to date:

Ozone generators may produce sufficient ozone to

create hazardous ozone concentrations in indoor

environments. The ozone emission rates vary as

a function of RH. NOx is produced as a

byproduct of ozone generation. The model RISK

appears to be useful for prediction of indoor

concentrations of ozone. Limited tests in the

research test house indicate that the feedback

control system provided by one manufacturer

maintains ozone concentrations at or below 50

ppb. On the other hand, though tests to date

indicate that operation of an ozone generator air

cleaner may result in somewhat lower

concentrations of some compounds, greater

exposure to formaldehyde and other aldehydes

and organic acids is likely to result. (EPA

Contact: Mark A. Mason, 919-541-4835.

mason.mark @epa.gov)

Figure 5. The relationship between ozone generation rate and

RH for three ozone generator air cleaners.

Figure 6. NOx emission rates for selected ozone generator air

cleaners determined at 50% RH.

Figure 7. Ozone concentration out of doors and in a room of the

research test house with ozone sensor-controller system of the

ozone generator air cleaner activated.
FIRST CLASS MAIL

POSTAGE AND FEES PAID

EPA

PERMIT No. G-35

EPA’s Indoor Environment Management Branch is cosponsoring

Indoor Air 2002

the largest international conference dedicated to

scientific and professional research in the indoor air sciences.

The conference will be held in Monterey, California, June 30 to July 5, 2002.

Plan now to attend this important event.

Abstracts must be submitted by October 1, 2001. Further information

is available from the web site at www.indoorair2002.org.

United States

Environmental Protection Agency

National Risk Management Research Laboratory

Indoor Environment Management Branch

MD-54

Research Triangle Park, NC 27711

Official Business

Penalty for Private Use

$300

EPA/600/N-01/002, Spring/Summer 2001

An Equal Opportunity Employer