United States
               Environmental Protection
               Agency
National Risk Management
Research Laboratory
Research Triangle Park, NC 27711
               Research and Development
EPA/600/SR-96/138  December 1996
EPA      Project Summary
               Evaluation  of Styrene
               Emissions from  a  Shower  Stall/
               Bathtub Manufacturing  Facility
                Larry Felix, Randy Merritt, and Ashley Williamson
                 Current EPA emission  factors (AP-
                42) for styrene emissions from the pro-
                duction of polyester-resin-reinforced
                plastic products represent a compos-
                ite of spraying and post-spraying emis-
                sions (from curing molds) from shower
                stall/bathtub manufacturing plants that
                use compressed-air-powered spray
                guns to apply catalyzed styrene resins
                to prepared molds. Because each step
                of manufacture (gel coating, first-stage
                spray lay-up, and second-stage spray
                lay-up) creates large surface areas from
                which  volatile  styrene monomer can
                evaporate, non-spraying emissions can
                constitute a large fraction of the sty-
                rene emitted to the atmosphere. Thus,
                it is of interest to quantify the level of
                non-spraying styrene emissions char-
                acteristic of this industry to validate
                current emission factors for spraying,
                as well as to develop emission factors
                for emissions not directly related to a
                spraying activity.
                 In this study, emissions were mea-
                sured at a representative  facility (Eljer
                Plumbingware  in Wilson, IMC) that
                manufactures  polyester-resin-rein-
                forced shower  stalls and  bathtubs  by
                spraying styrene-based  resins onto
                molds in vented, open, spray booths.
                Styrene emissions were characterized
                for the three stages of manufacture by
                measuring  styrene  concentrations at
                the vents of spray booths  used in each
                part of the process. In addition, sty-
                rene concentrations were  measured at
                each ventilation fan exhaust. Emission
                levels were determined  using EPA
                Method  18 to obtain integrated emis-
                sions samples  and  total  hydrocarbon
                analyzers to measure continuous emis-
                sions levels during the EPA Method 18
                sampling.
  Analysis of the  EPA  Reference
 Method data indicates that: (1) styrene
 monomer is the only volatile organic
 compound released in this process; (2)
 overall, approximately 4% of all mate-
 rial sprayed is lost to atmospheric emis-
 sions as styrene (approximately 19%
 of styrene sprayed); and (3) emissions
 vary for each phase  of manufacture,
 with post-spraying emissions of sty-
 rene (from curing molds) constituting a
 large part,  approximately 29%, of  all
 emissions.
   This Project Summary was developed
 by EPA's National Risk Management
 Research  Laboratory's  Air Pollution
 Prevention  and Control Division, Re-
 search Triangle Park, NC, to announce
 key findings of the  research project
 that is fully documented in a separate
 report of the  same title (see Project
 Report ordering information at back).

 Introduction
  Current EPA emission factors (AP-42)
 for styrene emissions from the production
 of polyester-resin-reinforced plastic prod-
 ucts do not specifically  account for post-
 spraying emissions (from curing molds)
 from shower stall/bathtub manufacturing
 plants that use compressed-air-powered
 spray guns to apply catalyzed styrene res-
 ins to prepared molds. Because each step
 of manufacture creates large surface  ar-
 eas from which volatile  styrene monomer
 can  evaporate, post-spraying emissions
 can constitute a large fraction of the sty-
 rene emitted to the atmosphere. Thus, it
 is of interest to quantify the level of spray-
 ing and post-spraying  styrene emissions
 characteristic of this industry to validate
 current emission factors for spraying,  as
 well  as to  develop emission factors  for
 post-spraying emissions.

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  Shower stalls and  bathtubs are among
the many products fabricated from liquid
polyester resin that have been  extended
with various inorganic filler  materials and
reinforced with glass fibers. These com-
posite materials are often referred to col-
lectively as fiberglass-reinforced plastic or
"fiberglass." Depending on the size, shape,
and  intended  use,  any  one of several
manufacturing processes can be used for
fabrication. For the manufacture of shower
stalls  and  bathtubs,  the preferred tech-
nique is  spray lay-up or sprayup.  All of
these processes involve the application of
a liquid resin that  is mixed with a catalyst
to initiate polymerization. In polymeriza-
tion, a liquid unsaturated polyester is cross-
linked with a vinyl-type monomer, usually
styrene, by the action of the catalyst. Com-
mon catalysts are organic peroxides, typi-
cally methyl ethyl  ketone peroxide or ben-
zoyl peroxide. Resins may contain inhibi-
tors to avoid self-curing during  resin stor-
age, and promoters to allow polymeriza-
tion to occur at lower temperatures.
  In the  production of fiberglass shower
stalls  and bathtubs  exhaust air from the
spray booths used for mold-coating and
plant ventilation air  outlets  represent the
major point sources of VOC emissions.
Thus, at a particular facility, the number of
manufacturing steps that involve the spray-
ing  of styrene-based resins, the amount
of styrene sprayed in each step of manu-
facture, and the amount of styrene that is
volatilized during the spraying and curing
of molds  determine the amount of styrene
emitted to the atmosphere.
  This study was undertaken to quantify
styrene emission factors at a shower stall/
bathtub  manufacturing plant determined
by the EPA to be  a representative facility.
Once  styrene emissions were measured,
the emissions  measurements  and raw
material usage data  from the plant were
used  to  determine  emission factors for
each phase in the manufacturing process.
  Testing was  carried out  at Eljer
Plumbingware, Wilson, NC,  and was part
of a larger effort that  also  involved  the
evaluation of a pilot-scale liquid chemical
scrubber  for styrene  removal.  Styrene
emissions measurements were originally
scheduled for the  week of June  14, 1993,
and the liquid chemical scrubber evalua-
tion was originally scheduled for the fol-
lowing week.  Because  the plant was op-
erating on a 4-day production week dur-
ing this time (Monday through Thursday),
instead of the 5-day production week that
had been expected, emissions testing had
to be extended through Monday, June 21,
1993, to obtain a suitable set of emissions
data. A full  day of testing  could  not be
carried out on Monday because portions
of that day had to be devoted to preparing
for the upcoming liquid chemical scrubber
evaluation.
  Section 2 of the  full project report con-
tains a detailed description of the facility
and sampling locations. Detailed descrip-
tions  of  the  sampling  methodology  are
presented in Section  3  and the results of
this evaluation along  with a discussion of
these results are presented in Section 4.
  The quality assurance and  quality con-
trol  measures taken  during this evalua-
tion,  as well as the results of these mea-
sures, are contained  in the Quality Con-
trol Evaluation Report as Appendix A. This
project summary  briefly  addresses  the
methodology and  emission  rate conclu-
sions from the study. More detailed infor-
mation can  be  obtained from the report
sections described  above.
  Two methods were  used to measure
styrene emissions.  A heated Tedlar™ bag
sampler was used  to  obtain an integrated
sample of the contaminated air exiting  a
representative point in  each process ex-
haust vent.  Concurrently,  styrene  emis-
sions were measured on a  continuous ba-
sis using a total hydrocarbon  (THC) ana-
lyzer equipped  with flame  ionization  de-
tectors. Sample times ranged from 40 to
45 minutes,  typically the time required to
spray eight  to ten  molds.  Sample times
were dictated by the plant production rate
and the time available for sampling during
a particular period  of spraying.
  Table 1 presents average styrene emis-
sions as  a  function of the area sprayed,
the total mass that was sprayed, and the
total  amount of styrene that was sprayed.
Styrene  emissions based  on  measure-
ments with  the THC analyzers were gen-
erally greater than those  determined by
Method 18. This result is somewhat unex-
pected because one might suspect that
some styrene would  be lost  in the long
heated sampling lines used to convey the
ventilation air samples to the THC analyz-
ers. Apparently, that was not the case for
these measurements. However, as Table
1 shows,  within the  uncertainty of the data,
styrene  emissions as  determined from
THC data and  from  Method  18 data do
overlap. It should be emphasized that be-
cause of the lack of multiple  measure-
ments, no uncertainty could be determined
for styrene  emissions  not captured by
spray booth exhaust fans (based on THC
analyzer  data).  Therefore,  the uncertain-
ties in Table 1 are minimum values. The
lack  of multiple  measurements for such
emissions is especially unfortunate  be-
cause styrene emissions not captured by
active spray booth  exhaust fans are one
of the  largest  sources  of styrene emis-
sions.
  Research conducted subsequent to the
above  analysis of test results has also
shown  differences between EPA Method
18 measurements of styrene emissions
and those using  THC  analyzers. How-
ever, the  reason for  these  differences
remains the subject of research.  It  has
been suggested that in the  Method  18
procedure styrene can  polymerize  be-
fore analysis and may also have a very
low vapor pressure at stack or instru-
ment conditions.  Both of these condi-
tions would  result in a lower measure-
ment for styrene.
  Although it is not  specifically noted in
AP-42,  it is  reasonable to assume that
styrene emission factors cited in this stan-
dard for polyester resin plastics products
fabrication include emissions not captured
by active spray booths. Thus, in order to
compare the results obtained  in this study
with those cited in AP-42, it is necessary
to apportion non-spray booth emissions
to those parts  of the process associated
with spraying operations: gel coating,  lay-
up, and back-up. When such an appor-
tionment is  carried  out,  with  the  data
obtained at Eljer, the following emission
factors are obtained:
  • Gel Coat - 47.5% of the styrene
    sprayed in that phase of manufac-
    ture
  • Lay-Up -  20.0%  of the  styrene
    sprayed in that phase of manufac-
    ture
  • Back-Up  -  12.1%  of the  styrene
    sprayed in that phase of manufac-
    ture
  These data  suggest that spray booth
emissions are  higher than those cited in
AP-42  for gel  coating  and spray lay-up.
AP-42  cites a value from 26% to 35% of
styrene monomer being emitted  for gel
coat that contains no vapor suppressing
additives (as was the case at Eljer). Like-
wise, these results show that when non-
spraying emissions  are apportioned to
each part of the manufacturing  process
nearly 48% of the styrene in the gel coat
mix is lost to the atmosphere.
  As might be  expected AP-42 makes no
distinction between styrene emissions from
lay-up  booths  or from back-up booths,
and indicates that with vapor suppressing
additives in the mix, from 3% to 9% of the
styrene sprayed in this operation is emit-
ted. If vapor-suppressing additives are not
added  to the mix, emissions  rise to from
9% to  13%  of the styrene sprayed. At
Eljer, vapor suppressants  are added to
the lay-up and back-up mix. However,

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Table 1. Styrene Emissions for Each Part of the Manufacturing Process

(a) Styrene Emissions per Unit Area of Mold Sprayed
                                                       THC Analyzer
                                                                                                    EPA Method 18
Emissions from:
Gel Coat Booths
Lay-Up Booths
Back-Up Booths
Non-Spray Booth Emissions
All Emissions
Styrene (g/m2)
  110.5
  116.0
   68.7
   83.7
  378.9
Pop. Std. Dev. (g/m2)
      21.2
      43.1
       3.8
     N/A
      48.1*
Styrene (g/m2)
   69.5
   85.5
   51.9
   83.7
  290.6
Pop. Std. Dev. (g/m2)
     26.4
     28.3
     12.6
     N/A
     40.7*
(b) Percent of Total Mass Used in Each Stage of Manufacture That Was Emitted as Styrene
                                                       THC Analyzer
                                                       EPA Method 18
Emissions from:
Gel Coat Booths
Lay-Up Booths
Back-Up Booths
Non-Spray Booth Emissions
All Emissions
Styrene (%)
14.3
3.4
2.4
1.2
5.4
Rel. Std. Dev. (%)
2.7
1.3
1.5
N/A
0.7*
Sytrene (%)
9.0
2.5
1.8
1.2
4.2
Rel. Std. Dev. (%)
3.4
0.8
0.4
N/A
0.6*
c) Percent of Styrene Used in Each Stage of Manufacture That Was Emitted
	THC Analyzer
                                                       EPA Method 18
Emissions from:
Gel Coat Booths
Lay-Up Booths
Back-Up Booths
Non-Spray Booth Emissions
All Emissions
Styrene (%)
   44.4
   16.1
   11.4
    5.3
   24.2
Rel. Std. Dev.
       8.5
       6.0
       0.6
     N/A
       3.3*
Styrene (
   27.9
   11.9
    8.6
    5.3
   18.6
Rel. Std. Dev. (%)
      10.6
       3.9
       2.1
    N/A
       2.8*
'Minimum estimate. Assumes each process independent with no contribution from the non-spraying emissions component.

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the levels of styrene emissions measured
there suggest that the emissions levels
are probably higher than what AP-42 cites
as typical for non-vapor suppressed emis-
sions, particularly for the lay-up phase of
manufacture.  Thus, results calculated ac-
cording  to the above apportioning proce-
dure show that styrene emissions to the
atmosphere averaged 20% of the styrene
sprayed in  the lay-up booths and 12% of
the styrene sprayed in  the single back-up
booth.
  These generally higher-than-expected
emission levels may be  due,  at  least in
part, to  the nature of the process. At the
Eljer facility (determined by the EPA to be
a representative facility) molds that have
been sprayed  are  frequently left  near the
mouths of spray booths where spraying is
in  progress. Hence, styrene evolved from
a  curing mold can  be captured  by an
adjacent spray booth. While this practice
is  not common in the gel coat booths
(because of limited space  in front of the
booths at the Eljer facility), this practice is
an integral  part of the manufacturing pro-
cess for the latter two stages of spraying.
In  fact,  at any one time, it is common for
as many 15 molds to be in various stages
of manufacture in the  general vicinity of
the lay-up and  back-up booths. Also, molds
are generally  left  in a lay-up booth  be-
tween sprayings where the surface of the
mold  is rolled flat. In AP-42 it  is noted
that styrene emissions are  increased by
such  manual rolling.
  Finally, AP-42 provides no separate es-
timate  of styrene emissions not captured
by spray  booths. While such  emissions
are certainly a function of ventilation sys-
tem design and the specific equipment at
a given facility, at Eljer it was found that
6% of all the styrene sprayed  exits  the
facility  through openings other than spray
booth exhausts.  As noted in Table 2, this
corresponds to from 22 to  29% (depend-
ing  on the measurement method) of  all
styrene emitted to the atmosphere; thus,
styrene emissions not captured by spray
booths represent a source of styrene emis-
sions as great as (or possibly greater than)
styrene emissions associated with any one
of the spraying operations.
Table 2. Distribution of Styrene Emissions from Each Part of the Manufacturing Process, Including Styrene Emissions Not Captured by Spray Booths
Date
                        From THC Analyzer Measurements
                Gel               Back-
                Coat     Lay-Up   Up       Non-      All
                Booths   Booths   Booths   Spraying   Sources
                                      From Method 18 Measurements
                            Gel                  Back-
                            Coat       Lay-Up    Up       Non-
                            Booths     Booths    Booths   Spraying
                         All
                         Sources
6/15/93
6/16/93
6/17/93
Average
29.9
29.2
29.2
29.4
30.2
30.5
30.6
30.5
17.9
18.1
18.2
18.0
22.0
22.2
22.0
22.1
100.0
100.0
100.0
100.0
24.5
24.0
24.0
24.2
29.1
29.3
29.5
29.3
17.6
17.8
17.9
17.7
28.8
28.9
28.6
28.8
100.0
100.0
100.0
100.0

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 Larry Felix, Randy Merritt, and Ashley Williamson are with  Southern Research
   Institute, Birmingham, AL 35255.
 Bobby E. Daniel is the EPA Project Officer (see below).
 The complete report, entitled "Evaluation ofStyrene Emissions from a Shower Stall/
   Bathtub Manufacturing Facility,"(Order No. PB97-125439; Cost: $21.50, subject to
   change) will be available only from:
         National Technical Information Service
         5285 Port Royal Road
         Springfield, VA 22161
         Telephone: 703-487-4650
 The EPA Project Officer can be contacted at:
         Air Pollution Prevention and Control Division
         National Risk Management Research Laboratory
         U. S. Environmental Protection Agency
         Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati,  OH 45268

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