EPA/600/A-92/145
92-139.15
Using a Flame lonization Detector (FID) to Continuously
Measure Toxic Organic Vapors in a Paint Spray Booth
Jamie K. Whitfield,
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory. MD-61,
Research Triangle Park, NC 27711
Gary B. Howe, Bruce A. Pate,
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, NC 27709
and Joseph D. Wander
USAF Civil Engineering Laboratory (-HQ AFCESA/RAVS)
Tyndall AFB, FL 32403-6001
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92-139.15
INTRODUCTION
U.S. Air Force (AF) industrial operations procuring and
maintaining equipment and facilities are the greatest sources of
volatile organic compound (VOC) and hazardous air pollutant (HAP)
emissions at AF installations. These emissions are subject to
stringent environmental regulations that have been evolving for
two decades, and are expected to continue their evolution for
decades to come. The USAF has stated its commitment to complying
with the new environmental standards, but two considerations
prevail: (1) maintaining the current standard of workplace
safety, and (2) keeping the cost of the emission control as low
as possible.
Program History
The AF Civil Engineering Laboratory (CEL) and Environmental
Protection Agency's (EPA's) Air and Energy Engineering Research
Laboratory (AEERL) began a study of AF air compliance issues in
1986. The initial study showed that paint spray booths at several
sites tested would not comply with potentially more stringent
emission regulations unless emissions levels were lowered.1 To
combat this problem, the report suggested that exhaust
recirculation be considered as a means of decreasing the volume
of exhaust air requiring treatment and, therefore, lowering the
pollutant emissions. Unfortunately, this innovative
recommendation met opposition in the AF industrial hygiene (IH)
community.
The primary objection raised by AF IH personnel references
29 Code of Federal Regulations (CFR) 1910.107 (d) (9),2 which
explicitly states that recirculation of emissions from paint
spray booths is prohibited. Upon further consideration,
Occupational Safety and Health Administration (OSHA) issued a
letter3 to EPA stating that the regulation in question pertains
to fire safety and not to personnel toxic exposures. Instead,
OSHA referenced 29 CFR 1910.10004 for toxic exposures, which does
not prohibit recirculation. 29 CFR 1910.107 (d) (9) was not
intended to prohibit recirculation or institution of innovative
technologies. Rather, it ensures that booth operations remain
within safe levels. Thus, under the OSHA de minimus rule, a booth
may use recirculation if the booth irrefutably complies with 29
CFR 1910.1000. Based on this compromise, a demonstration study
was developed at Travis Air Force Base (AFB), California.
The CEL/AEERL team conducted two site studies of spray
booths, and will conduct more studies at Travis AFB in June 1992.
The first study was conducted at McClellan AFB, CA. It determined
that fluidized-bed incineration and an adsorption/desorption
preconcentration process will effectively remove VOCs
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92-139.15
from exhaust gas. The disadvantage of both systems is that the
estimated cost of treating the full circulating stream may be
exorbitant5 depending on the volumetric flow to be treated.
A second study was conducted at Hill AFB, Utah. The spatial
distribution of volatile, metal, and isocyanate species was
measured in a horizontal-flow, waterfall booth. The results show
that the toxics concentrate near the bottom of the booth and in
the painter's breathing zone.6 The concentration in the painter's
breathing zone appears to result from localized eddy currents in
the air stream, which are caused by the presence of the painter's
body as an obstacle. Armstrong Laboratory's IH newsletter has
cited excessive exposures to toxic metals, under just such
conditions, in a context that implicitly recommends wearing a
respirator while painting in a horizontal-flow booth.7
Travis AFB serves as the test site for two studies to be
conducted. Both studies are designed such that workplace safety
standards are not sacrificed and comply with OSHA regulations and
directives. For example, during the study, an informed volunteer
painter will be equipped with a supplied air respirator and skin
protection. This gear is commonly required by AF shops conducting
spray painting operations. Also, air toxic measurements will be
taken inside and outside the respirator and, as an added safety
measure, the painter will be medically evaluated before and after
painting tests.
Also incorporated into the Travis AFB study is the design of
a fail-safe diversion system for converting the recirculating
flow pattern back to "straight-through" ventilation. This relies
upon the use of a flame ionization detector (FID) to monitor the
concentration levels within the booth. The information obtained
from using this instrument for measurement gives a total
hydrocarbon analysis, as opposed to a speciated compound
analysis. However, the compound of interest can be identified by
calculating its percent composition of the total, assuming
complete volatilization of the paint system's components.
The Travis AFB study will provide an experimental basis for
evaluating the impacts of exhaust modifications on air toxic
emission rates and on attainment of IH standards.
Project Objective
This project, which is a component of the justification
process for the experimental evaluation of flow-splitting and
exhaust recirculation, is the final step in preparation for
evaluation of these techniques. Although the immediate purpose is
to establish that the Travis AFB test does not present an
extraordinary health risk to the volunteer painter and other
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92-139.15
personnel participating on the testing team in the booth, the study
will also apply to any other volatile mixture of defined
composition in a paint spray booth.
Specifically, the objective is to demonstrate experimentally
that the response of a FID is adequate for determining, reliably,
that the concentration of toxic compounds will remain, at all
times, less than 25% of the short term exposure limit (STEL).
This FID system must activate when: (1) the instantaneous
concentration exceeds 25% of the STEL8" for the coating and
catalyst, NSN 8010-01-336-3036, used exclusively during the
demonstration, (2) a concentration of 23% of the STEL is
maintained for 15 consecutive minutes, or (3) a concentration of
20% of the STEL has been measured during a total of 180
nonconsecutive minutes during a single painter's shift. This
mechanism ensures that the exposure standards specified in 29 CFR
1910.1000 are not exceeded at 15-minute or 8-hour time-weighted
levels during the test.
The purpose of generating these data is to confirm that,
when accurately set and properly maintained and calibrated, the
FID can reliably detect any excursions above an arbitrarily
selected threshold, sound an alarm to alert site personnel, and
trigger devices that reconfigure the ventilation system and/or
disable the spray gun and intercede before harmful exposure
develops during the spray booth operation.
EXPERIMENTAL DESIGN
Continuous Analyzer
A total hydrocarbon FID from Ratfisch Instruments, model
RS-55CA, was used for the project. The analyzer is configured
with four measuring ranges: 0-100, 0-1000, 0-10,000, and
0-100,000 parts per million as carbon (ppmC). Sample gas was
introduced into the hydrogen flame through a sample capillary at
a low flow rate. The FID response was based on the concentration
of the VOCs in the sample gas and the type of compounds present.
The analyzer output consisted of both a 0 to 1 V analog recorder
signal and a front panel display.
Test Mixture Composition
This project specifically addresses the health risks
attending the use of the polyurethane coating and aliphatic
isocyanate catalyst, NSN 8010-01-336-3036. Lists of the hazardous
components for the specified coating and catalyst were identified
in the manufacturer's Material Safety Data Sheets (MSDSs). The
weight percentage of each component was used to calculate a
combined weight in the mixture (3:1 ratio by weight of coating to
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92-139.15
catalyst), from which the weight percentage was calculated based
on the VOC content only. The calculated composition of the
mixture is shown in Table I.
TABLE 1. COMBINED COATING/CATALYST SOLVENT COMPOSITION8
Compound
ri-Butyl acetate
Ethyl-3-ethoxypropionate
Toluene
Xyleneb
Methyl isobutyl ketone
Methyl ethyl ketone
Ethylbenzene
PG.ME acetate*
2, 4-Pentanedione
Wt. % (NSNC 8010-01-336-3036)
Coating Catalyst Combined
5
5
1
1
5
5
0.1
1
5
5
20
0
5
35
0
0
0
0
5
8.75
0.75
2
12.5
3.75
0.075
5
0.75
3.75
wt. % of voc
content
13.4
23.4
2
5.4
33.5
10
0.2
2
10
a3:1 mixture (by weight)
bSubstituted xylene for "C8 & CIO aromatic hydrocarbon" from MSDS for
03GN240CAT.
cNational Stock Number
dPropylene glycol monomethyl ether (PGME) acetate is the common name for 1-
Methoxy isopropyl acetate.
Calculation of Exposure Limit
The STEL for each component is shown in Table 2. Where available,
the STEL given corresponds to the OSHA permissible exposure limit (PEL).
For compounds not having an OSHA PEL-STEL, the STEL as assumed to be 1.5
times the manufacturer-recommended Threshold Limit Value (TLV)-time
weighted average (TWA).
Application of the ACGIH rule*b for additive effects to the data
in Table 2 resulted in a calculated STEL for the coating and-catalyst,
NSN 8010-01-336-3036, of 350 mg/m3. This value is based on the
assumption that volatilization is complete and uniform; although this
is not strictly correct, toxicity of the less-volatile constituents is
greater, so the calculated value underestimates the "true" exposure
limit. (Comparable STELs were calculated for several other
polyurethane coatings presently in AF inventory, but a significantly
lower value was calculated for MIL-P-23377 primer.)
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TABLE 2. COMBINED COATING/CATALYST STEL CALCULATION
Compound
n-Butyl acetate
Ethyl-3 ethoxypropionate
Toluene
Xylene
Methyl isobutyl ketone
Methyl ethyl ketone
Ethylbenzene3
PGME. acetateb
2, 4-Pentanedione
Wt. % (of
VOC)
13.4
23.4
2.0
5.4
33.5
10.0
0.2
2.0
10.0
STEL,
aig/m3
950
447
560
655
300
885
545
810
123
Source of STEL
OSHA PEL
Manufacturer
OSHA PEL
OSHA PEL
OSHA PEL
OSHA PEL
OSHA PEL
Manufacturer
Manufacturer
Mixture STEL=1/(0.134/950+0.234/447+0.02/560+0.054/655+0.335/300+0.1
/885+0.002/545+0.02/810+0.1/123) = 350 mg/m3
"Omitted from mixture since weight % is insignificant.
bPropylene glycol monomethyl ether (PGME) acetate is the common name
for 1-Methoxy isopropyl acetate.
Test Mixture Preparation
Nine mixtures were prepared for characterizing the analyzer
response in the 0-1000 ppmC range and three mixtures were prepared for
the 0-100 ppmC range. The highest concentration mixture was prepared
by vaporizing a known mass of a liquid mixture and flushing it into an
evacuated aluminum cylinder with a known volume of dry air. The liquid
mixture was prepared by adding a given mass of each compound to a
glass vial, based on the weight percentages shown in Table 1.
Subsequent mixtures were prepared by withdrawing a portion of
the gaseous mixture and refilling the cylinder with dry air. A bourdon
tube vacuum/pressure gauge was used to measure accurately cylinder
pressures for determining test mixture concentrations.
Test Mixture Analysis
During normal field operation, the Ratfisch RS-55CA analyzer uses
an internal pump to draw a high volumetric flow rate of sample through
a sample port, past a tee at the FID, and then through a back-pressure
regulator before exhausting through the bypass port. The back-pressure
regulator is used to adjust the sample gas pressure, which controls
the flow rate of sample gas through a capillary and into the FID. The
normal pressure is 2 psig (13.8 kPa).
Since the sample gas mixture in this study was contained in an
aluminum cylinder at approximately 40 psig (275.8 kPa), operation of
the analyzer was modified. The internal sample pump was not operated,
but was left in the sample flow path. To conserve sample test mixture,
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92-139.15
the bypass port was fitted with a shutoff valve. When this valve was
closed, the sample back-pressure regulator was not functional. The
sample gas pressure was regulated with an in-line single-stage
pressure regulator installed at the outlet of the test mixture
cylinder. Similar regulators were used to set the gas pressures for
the propane calibration gases and the zero air.
The FID was operated with normal settings for hydrogen fuel (6 psig
or 41.4 kPa) and combustion air (11 psig or 75.8 kPa).
Each of the test mixtures and calibration gas mixtures was sampled
in the analyzer, and the FID response was recorded on a strip chart
recorder. The in-line pressure regulator was adjusted so that the same
sample pressure was used in all analyses.
RESULTS
Propane Calibration and VOC Mixture Analysis Results
The analyzer was first calibrated for the 0-1000 ppmC range. With
zero air passing into the sample inlet port, the zero potentiometer
was adjusted to produce a zero output from the FID. Then, with a
standard containing 525 ppmC propane in air passing into the sample
inlet port, the span potentiometer was adjusted to produce an analyzer
output reading corresponding to 525 ppmC. Three additional
concentrations of the standard containing propane in air were also
analyzed.
After changing the analyzer range setting to 0-100 ppmC, the zero
and span were adjusted while sampling zero air and a standard
containing 46 ppmC propane in air standard, respectively. Two
additional concentrations of the standard containing propane in air
were also analyzed in this range.
To illustrate the response of characteristics of the analyzer to both
propane and the VOC test mixture, plots of analyzer response versus
concentration for both the 1000 and the 100 ppmC ranges a^re shown in
Figures 1 and 2. The concentrations for the propane and the solvent
mixture are expressed in milligrams per cubic meter. Linear regression
analysis was performed for each set of data, and the results are shown
in each figure, respectively.
Both of these figures display straight-line fits to data generated
by passing the solvent mixture, representative of the volatile fraction
of the coating and catalyst, and the calibration gas, propane, through
the RS-55CA FID. The results of the linear regression analyses of the two
figures further support the statement that FID response to the organic
analytes was linear over the entire range measured and well below the
STEL calculated for the coating and catalyst, NSN 8010-01-336-3036, or
any other paints for which the STEL was estimated.
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100
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92-139.15
-Propane
Linear Regression
Slope = 1.68
y-intercept = -6.59
R squared = 0.9998
I
I
Solvent Mixture
Linear Regression
Slope =1.078
y-intercept = 14.87
R squared = 0.994
100 200 300 400 500
Concentration, mg/m3
600
700
Figure 1. Ratflsch RS-55CA Calibration 0-1000 ppmC Range.
o
a.
o.
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92-139.15
DISCUSSION
The test at Travis AFB will use a servo-actuated set of'flap valves
to convert a horizontal-flow spray booth from straight-through
(single-pass) circulation into a partially recirculating system. During
recirculation, a portion of the exhaust stream will be filtered, mixed
with an equal•volume of fresh air, and returned via an intake filter to
the circulating air stream. For the test, the exhaust stream will be
released without treatment. However, the concentrations of air toxic
materials will be measured and the acquired data will be used to estimate
the cost and effect of application of available technologies for
purification of the reduced exhaust stream prior to releases.
Similar measurements will also be made on the recirculated stream to
evaluate the impact on IH safety standards. Calculations indicate
that, as long as the particulate control system (dry filters) is
maintained and operated properly, the increase in toxic exposure will
be negligible in comparison to ambient spray booth concentrations.
However, no calculation can exclude all potential risk of overexposure
to personnel in the spray booth. A prudently conservative attitude
dictates that the experiment be conducted under circumstances that
minimize both the risk of exposure and the extent to which
overexposure could occur. Risk minimization is the purpose of
incorporating the FID into the study.
As designed, the recirculating booth will include the FID
immediately behind the intake filters. The FID will continuously
•measure the concentration of combustible airborne volatile substances
and report to two triggering devices. As in the case of the solvent
mixture, no other sources of toxic substances exist, so any additional
contributions by non-halogenated combustibles will overestimate the
exposure.
The first triggering device will respond immediately to any
instantaneous excursion above 350 mg/m3, the calculated STEL.
Overexposure would then be limited to the air volume passing into and
through the intake plenum and booth during the fraction of a second
required for the servos to switch the flap valves to a fresh air intake.
The second triggering device, a computer, will store a record of the
FID outputs at a fixed sampling rate, and convert to straight-through
ventilation if either of the following two criteria is met: 1) a period
of 30 consecutive seconds is maintained at 87.5 mg/m3 (25% of the STEL),
or 2) a total of 180 nonconsecutive minutes at 87.5 mg/m3 (25% of the
STEL) is accumulated during a single painter's shift.
The results in Figure 1 include, as the lowest point in the range,
105 mg/m3, and the results in Figure 2 include, as the highest point in
the range, 77 mg/m3. Thus, an extrapolation is made to cover the range
from 77 to 105 mg/m3 that includes the point 87.5 mg/m3, or 25% of the
STEL. The results in Figures 1 and 2 demonstrate that the FID exhibits
sensitivity and linearity of response adequate to discriminate organics
accurately below 87.5 mg/m3.
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92-139.15
CONCLUSIONS
This study has demonstrated linear and similar responses of a
Ratfisch RS-55CA FID to a solvent mixture identical to the volatile
organics in the coating and catalyst, NSN 8010-01-336-3036, and to the
calibration gas, propane, used in field calibrations of the FID.
Sensitivity and linearity have been shown to extend from 715 to 45 mg/m3,
which brackets the calculated STEL and lower action thresholds.
Monitoring is maintained constantly, and, under field conditions,
equilibration occurs rapidly and analysis and output transpire in
milliseconds. As a trigger for fail-safe conversion from recirculation
mode into a straight-through booth configuration, the FID may confidently
be expected to initiate a corrective response before a transient
elevation of VOC concentrations overexposes area personnel.
REFERENCES
1. J. Ayer and D. Wolbach, Volatile Organic Compound and Particulate
Emission Studies of Air Force Paint Booth Facilities;
Phase I, ESL-TR-87-55; EPA-600/2-88-071 (NTIS ADA19803Z), Air Force
Engineering and Services Center, Tyndall AFB, 1988.
2. 29 CFR Ch. 17, 1910.107, Occupational Safety and Health Standards;
Spray Finishing Using Flammable and Combustible Materials: Federal
Register, June, 1974, pp. 183-185.
3. T.J. Shepich, letter to S.R. Wyatt, U.S. EPA, 16 January 1990.
Reproduced as Appendix G of ESL-TR-89-35; EPA-600/2-90-051 (NTIS
ADA198092), (Reference 5).
4. 29 CFR Ch. 17, 1910.1000, Occupational Safety and Health
Standards; Toxic and Hazardous Substances; Air Contaminants; Federal
Register, June 27,1974, pp. 598-599.
5. D.H. Ritts, C. Garretson, C. Hyde, et al.. Evaluation of
Innovative Volatile Organic Compound and Hazardous Air Pollutant
Control Technologies for U.S. Air Force Paint Sprav Booths. ESL-
TR-89-51; EPA-600/2-90-059 (NTIS ADA242508), Air Force Engineering and
Services Center, Tyndall AFB, FL, 1990.
6. J. Ayer and C. Hyde, VOC Emission Reduction Study at the Hill Air
Force Base Building 515 Painting Facility. ESL-TR-89-35; EPA-600/2-90-051
(NTIS ADA198092), Air Force Engineering and Services Center, Tyndall AFB,
FL, 1990.
7. J.F. Seibert, Ventilation Booths and Respirators, Armstrong
Laboratory Occupational and Environmental Health Newsletter, S.
Spradling, ed., Brooks AFB, TX, Volume 15, Issue 4, 1991, p.l.
8. American Conference of Governmental Industrial Hygienists,
1990-1991 Threshold Limit Values for Chemical Substances and Physical
Agents and Biological Exposure Indices, ACGIH, Cincinnati, OH, 1990.
(a) p.4; (b) pp. 43-45.
10
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AEERL-P-925
TECHNICAL REPORT DATA
(Please read iHSlructions on tlic reverse before completing)
1 REPORT NO.
EPA/6QO/A-92/145
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Using a Flame lonization Detector (FID) to Contin-
uously Measure Toxic Organic Vapors in a Paint
Spray Booth
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7.AUTHOR(sij.whitfield (EPA); G.Howe and B. Pate (RTI);
and J. Wander (USAF)
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, North Carolina 27709
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
CR815169-03
12. SPONSORING AGENCY NAME AND ADDRESS
EPA. Office of Research and Development
Air and Energ}r Engineering Research Laboratory
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper; 7/91-1/92
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES AEERL project officer is Jamie K. Whitfield, Mail Drop 61, 919 /
541-2509. For presentation at AWMA annual meeting, Kansas City, MO, 6/21-26/92,
16. ABSTRACT
paper repOrts the demon s tr ation of linear and similar responses of a
Ratfisch RS-55CA flame ionization detector {FID) to a solvent mixture identical to
the volatile organic compounds (VOCs) in the coating and catalyst (NSN 8010-01-336-
3036) and to the calibrating gas (propane) used in field calibrations of the FID. Sen-
sitivity and linearity have been shown to extend from 715 to 45 mg/cu m, which brac-
kets the calculated short-term exposure limit (STEL) and lower action thresholds.
Monitoring is maintained constantly and, under field conditions, equilibration oc-
curs rapidly (analysis and output transpire in milliseconds). As a trigger for fail-
safe conversion from recirculation mode to a straight- through paint spray booth con-
figuration, the FID may confidently be expected to initiate a corrective response be-
fore a transient elevation of VOC concentrations overexposes area personnel.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution Solvents
Spray Painting
Organic Compounds
Measurement
~ , ....
Conductivity
P.PROO.CEOBv
us DEPARTMENT OF COMMERCE
NATIONAL TECHN'CAL INFORMATION SERVICE
SPRNGCIE.D VA 22161
Pollution Control
Stationary Sources
Paint Spray Booths
Flame lonization De-
tectors (FIDs)
13 B
13 H
07C
06T
14G
11K
8. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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