United States
                  Environmental Protection
                  Agency	
Environmental Monitoring
Systems Laboratory
Research Triangle Park, NC 27711
                  Research and Development
EPA/600/S4-88/017 July 1988
f/EPA        Project Summary
                  Sampling/Analytical Method
                  Evaluation  for  Ethylene  Oxide
                  Emission  and Control  Unit
                  Efficiency Determinations
                  Joette Steger and William Gergen
                    The U.S. Environmental Protection
                  Agency   (EPA)  is   currently
                  considering  the  development of
                  regulations to control ethytene oxide
                  (EO) emissions  from  commercial
                  sterilization facilities. Therefore,  a
                  reliable sampling and analysis
                  method for measuring EO emissions
                  must be established. The method
                  must be capable of measuring total
                  EO emissions  and  must  be
                  applicable to determining  the
                  efficiency of EO control devices.
                    Measurement  of EO emissions
                  from  commercial  sterilization
                  facilities is not  a straightforward
                  process. The EO is emitted from the
                  chamber  or  control  unit  inter-
                  mittently, and the  emissions vary in
                  intensity and EO content. This report
                  describes  the results of a field
                  evaluation of a  semi-continuous
                  direct sampling procedure applicable
                  to commercial sterilization facilities.
                    The facility  chosen  for the  test
                  used  a mixture of  12/88  (w/w)
                  EO/dichlorodifluoromethane  (CFC-
                  12) as the sterilizing gas. Ethylene
                  oxide emissions to the  atmosphere
                  were  controlled using a  com-
                  mercially  available  aqueous
                  absorption-hydrolysis system.
                    Samples of the exhausted  gas
                  were  continually removed from
                  sample ports  located  before  and
                  after the EO  control unit. Ethylene
                  oxide and CFC-12 concentrations
                  were analyzed at regular intervals
                  using an on-line gas chromatograph
equipped with dual gas sampling
valves, columns, and flame ionization
detectors.  In addition, the oxygen
content of the gas exiting the control
device was measured at  selected
intervals.
  The volumetric flow rate from the
control device was  determined from
differential  pressure measurements
across two restricted orifice plates
Installed in parallel on the control
unit stack.
  The  method  was evaluated for
repeatability, precision,  and use-
fulness in determining the efficiency
of an aqueous  absorption-hydro-
lysis control system.
  This  Project Summary was
developed  by EPA's Environmenta/
Monitoring Systems  Laboratory,
Research  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
  A method for sampling and analyzing
ethylene oxide (EO) in the vent stream
from a sterilization chamber and a dilute
acid scrubber was field evaluated and the
method's usefulness for measuring
control unit  efficiency was determined.
The  U.S. Environmental Protection
Agency  listed  EO as a  possible
hazardous air pollutant, creating a need
for standardized sampling and analytical
method to consistently determine control

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equipment  efficiency.  The  evaluated
procedure used semi-continuous  direct
sampling  with on-line  gas  chro-
matographic analysis.
   Using  measured EO  mass flow rates
into and  out of the scrubber, scrubber
efficiencies  were  calculated.   A
throughput  efficiency was calculated
using the EO mass flow rates measured
at the inlet  and  outlet of the control unit
and a recovery  that was equated  to the
control unit efficiency  was  calculated
from the  weight of  EO charged into the
chamber  and the measured EO emission
at the outlet of the control unit.

Facility  Description
   The field evaluation was  conducted at
a commercial medical supply sterilization
facility  that has three 28  cubic  meter
chambers that use 12/88  sterilant gas.
The initial EO charge to the  chamber was
calculated using the weight  of the  supply
cylinders  before and  after  charging the
chamber.
   The sterilizer exhaust is  controlled  by
a  Chemrox DEOXX™ system,  a dilute
acid scrubber that hydrolyzes the EO to
ethylene  glycol. During the tests  the
scrubber  contained a mixture of dilute
phosphoric and sulfuric acid.
   Each chamber is equipped with a total
recirculating  pump with  a  gas/liquid
separator that  emits the  gas  to  the
DEOXX  system and recirculates  the
liquid to  the pump inlet. All of the tests
were  conducted  using  chambers
equipped with  oil-sealed pumps.
   The sterilization cycle is  automatically
controlled by a programmable  micro-
processor system that has  the capability
to control  and record the chamber
temperature,  chamber pressure, and
elapsed time from the start of the cycle.
The tested sterilization  cycles were
scheduled  so  that only one sterilizer
vented at a  time.
   Before the start of nine of the tests,
the chamber was evacuated to 2 pounds
per square  inch absolute (psia) and then
pressurized to 3.1  psia with steam. Next,
the chamber was  charged  to 23.9 psia
with 12/88  gas. During  each evacuation
and air in-bleed cycle, the  chamber was
evacuated to 2 psia and pressurized with
air to 13.9 psia.  For one test the chamber
was initially  evacuated  to  7 psia,
pressurized to 32.9 psia with 12/88 gas,
and  cycled between 7  and 13.9 psia
during each evacuation  and air  in-bleed.

Sampling Locations
   Samples were  acquired before and
after the  control unit. The scrubber inlet
sampling location, used  to obtain a
continuous sample of sterilizer chamber
exhaust, was midway  between  the
sterilizer outlet and  the  scrubber  inlet.
The exhaust was transferred from the
chamber outlet to the scrubber inlet via a
6-in.  diameter poly vinyl  chloride  (PVC)
duct. Sample was acquired with 3/16-in.
Teflon probe.  No  direct  flow  mea-
surements were made at this location.
   A  continuous sample of scrubber
exhaust was  obtained  and  volumetric
flow  measurements  were made  at the
scrubber outlet.  Exhaust  exited  the
scrubber  vertically through  a  6-in.
diameter  PVC ductwork  that exhausted
1.5 m  above roof  level. To measure
volumetric flow,  the  stack was modified
by installing  6-in.  diameter  PVC
ductwork and  two  butterfly valves to
divert the scrubber exhaust through one
of the parallel ducts, a 48-mm sampling
probe, two orifice plates in parallel, 1.9 m
[12.7  duct  diameters]  downstream of
their  respective  butterfly  valves, and 40
cm [2.7 duct diameters] upstream of
their  respective 90°  bends, and wet and
dry bulb temperature probes.

Procedures

Sampling Procedures
   Samples were  taken  simultaneously
from both sampling locations.

Ethylene Oxide Sampling
   Sample was  withdrawn into heated,
64-mm I.D., Teflon  lines using  Teflon-
lined diaphragm pumps. A 15-m  line
was used on  the inlet port  and a  30-m
line  was  used  on the outlet  port.
Stainless steel,  64-mm  tees were used
prior to the pumps to remove slipstreams
from  the  main  sampling  lines.  The
slipstreams were routed through heated,
6-port, gas sampling valves that  were
used to introduce the samples onto the
GC columns.  Prior to  the 6-port  valves
were  pumps  with   Teflon-lined
diaphragms and  stainless steel,  64-mm
I.D.,  toggle operated shut-off valves.
Stainless steel fine metering valves and
rotameters  were used after  the  6-port
valves  to control  the flow rates  of the
slipstreams.  Before  exhausting  to the
atmosphere, the slipstreams and  main
sample streams were  routed  through
dilute acid scrubbers to remove the EO.
   Testing  began  when the  DEOXX
scrubber  started to  exhaust  in
preparation for the  initial chamber
evacuation. Each test consisted of seven
evacuations,  the  initial chamber
evacuation, and pump down and  six air
in-bleeds and  subsequent evacuations.
Testing stopped  at the start of thdl
seventh air in-bleed. The start time and
end  time  of  the evacuations  were
identified by flow  or lack of flow across
the orifice plates.
   The sampling  lines were  continually
flushed with sample throughout the test
day.  Flow rates through  the slipstreams
that flushed the gas sampling loops were
maintained at 100 ml/min. Samples were
isolated in the 6-port valves  by closing
the  shut-off  valves  simultaneously.
When the rotameters indicated no flow,
the sample  loops were  at atmospheric
pressure, and the  samples were injected
into the GC.

   After the  first sample, samples were
acquired at three or four  minute intervals
until  the end of the  first  evacuation. For
the  second  through   the  seventh
evacuations  the first  sample  was
acquired at either  one, two or  three
minutes after the start of the evacuation.
Again, samples were acquired at three  to
four intervals.


Volumetric Flow Rate
Measurement
   Volumetric flow rate measurements  of
scrubber exhaust  were performed at the
scrubber  outlet  location  using  two
standard, squared-edged orifice  plates
with  standard pipe taps mounted  in
parallel ducts. The orifice diameters used
were 1.763-in. (4.48-cm) and 2.591-
in.  (6.58-cm).  Temperatures  were
measured using  a thermocouple  and a
pyrometer.

Moisture  Determination
   The percent moisture of the stack gas
was  determined by the wet bulb/dry bulb
method. Wet and dry  bulb  temperature
measurements were recorded at  least
once during each exhaust episode.

Molecular Weight Determination
   Nitrogen, oxygen,  water,  EO,  and
CFC-12  were considered  the  main
components of the sterilizer exhaust gas.
The  emissions of EO and CFC-12 were
continuously  monitored by  GC/FID.
Oxygen emissions were  measured with
Fyrite  oxygen indicator. The nitrogen
concentration was  determined  by
difference.

   Percent levels of oxygen were usually
measured once during each  evacuation.
For  several of the runs oxygen  was
determined  at 1- or 2-min  intervals  to
determine  the  dead  volume  of the

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scrubber system. Sample was removed
from the stack  upstream of  the  orifice
plates using an aspirator  bulb to pull the
sample from the stack.

Analytical Procedures
   The analytical method used for the
measurement of the EO and  CFC-12
was gas chromatography with  flame
ionization detection  (GC/FID). The dual
FID Varian 3400 GC was equipped with a
Nutech heated valve box containing two
6-port valves. An 0.25 ml loop was used
on the inlet sample line and a loop of 2
ml was  used  on the outlet sample line.
The analytical columns were 10 ft (3 m) x
1/8 in.  (3  mm) O.D. stainless  steel
columns containing 5% Fluorcol on 60/80
Carbopack  B.  The  FID electrometers
were  connected to Shimadzu  CR1-A
integrators.
   The GC  column  oven was operated
isothermally at 100°C, the injector oven
at 175"C, and the detector oven at
200 °C.  Nitrogen carrier  gas  flow rates
were 30 ml/min on the outlet channel and
60 ml/min on the inlet channel. Detector
support gas  flow rates of 30  ml/min  for
hydrogen and 300  ml/min for air were
used.
   The same FID electrometer range was
used for the  EO and CFC-12 on  the inlet
channel but the range  used varied from
10'9 to 10'11  depending on the inlet
sample concentration.   The FID
electrometer range was programmed on
the outlet channel. A range  of  10'1° to
10'12 was used for the EO and  10-8 to
10-1° was used for the  CFC-12. The
electrometer range was programmed to
switch  at 1.1  min  during  the first
evacuations and at  1.55  min  during the
second  through seventh  evacuations  for
optimum quantitation of both EO  and
CFC-12.
   Both  channels of  the  chromatograph
were  calibrated for  EO  and  CFC-12 at
the beginning  and  end  of the  day. At
least  one standard was  also analyzed
between tests.  Standards  were
purchased from Scott  Specialty  Gases,
Scientific  Gas Products,  and  MG
Industries  and   ranged  in  EO
concentration  of less than 1 ppmv to
20%  vol and in CFC-I2  concentration
from   1200  ppmv  to  62.5%  vol.
Calibration  curves consisted   of  a
minimum of three standards.

Calculations
   The data were reduced using LOTUS*
1-2-3  software.  Rounding  was
performed  at  the completion  of the
calculations.
   Ethylene  oxide  and  CFC-12
calibration  curves were  prepared  by
taking the logarithm of the peak area and
plotting that  logarithm  versus  the
logarithm of the  concentration. The EO
and CFC-12 concentrations were  inter-
polated  at  10-sec intervals  for the first
evacuations. Usually,  the  concentrations
were  assumed  to  increase linearly,
plateauing  at a maximum determined by
an average of  the data points after the
concentration versus  time curve leveled
off. In some cases the concentration was
assumed  to  decrease  linearly  after
reaching a  maximum  and  in other cases
the concentration was  assumed  to  be
constant throughout the evacuation.
   For  the second  evacuations  the
concentrations  were  assumed  to
decrease  linearly where enough data
were present to validate that assumption.
In most cases  an average concentration
was  used. In  all cases for  the third
through seventh  evacuations  average
concentrations were used.
   The  molecular weight of  the vent
stream  was the  sum of  the molecular
weight of each component multiplied by
the mole fraction of  that  component in
the vent stream. For the first evacuations
the oxygen was assumed to  decrease
exponentially from 20% to  0%  vol. In
several cases for the second evacuations
the oxygen was assumed  to increase
linearly; however, in  most cases either
the average of all measurements  was
used  or  a value of  19%  vol was
assumed.  For the third  through seventh
evacuations the measured value  was
used or, if  no measurements were taken,
a value of 20% vol was assumed.
   The EO mass flow rate into the control
unit was calculated based on the number
of moles  of gas  exiting  the  chamber
during each 2-min interval.  Using the
chamber pressure   and  jacket
temperature, the moles of  gas  leaving
the chamber were calculated  from the
ideal gas law, assuming that the chamber
gas did not significantly deviate from
ideal behavior at the chamber conditions
tested.
   The weight of EO entering the control
unit during  each time interval was given
by multiplying the moles of gas leaving
the chamber during each time interval by
the molecular weight of EO and the mole
fraction  of  EO in the gas. Summation of
the weights of EO entering the control
unit  during  each  time  interval
provided the total weight of EO entering
the control unit during the test period.
   The EO emission out  of  the control
unit was calculated based  on the pounds
of gas exiting the control unit during each
10-sec  interval. The weight  of EO
leaving the control unit during each  time
interval was given by multiplying the time
interval by the mass flow rate of EO
leaving the  scrubber  during  that  time
interval. The total weight  of  EO leaving
the control  unit  during  the  test  was
provided  by adding the weights  of EO
leaving the  scrubber  during each  time
interval.
   The total mass flow rate of gas was
calculated from the pressure drop across
standard  orifices  using equations taken
from the American Society of Mechanical
Engineers Research Committee on Fluid
Meters  Report   "Fluid   Meters—Their
Theory and  Application,"  6th ed.  1971
Values for  the specific heat ratio were
obtained  form Perry's  Chemical
Engineers' Handbook.
   A Houston  Instrument  Digitizer  was
used  to  convert the stripchart  lines
representing  continuous pressure
readings  across  the orifice plates  into
numerical values.
   The mass rate of EO flow out of the
control unit was then given by:

    m = 60 X w X (PEO X MWEOVMWav   (1)

where:
    m = mass flow rate of EO, Ib/min,
    w = total gas flow rate, Ib/s,
  PEO  = EO concentration, percent by
        volume  = ppmv/106,
MWav = molecular weight of the vent
        gas, and
MWEO = molecular weight  of EO

   A throughput efficiency  was calculated
using the emissions into and out of the
control unit. The throughput  efficiency
(ET) is given by:
     = lOOx(W,n-Wout)/Wu
(2)
   A recovery  efficiency was calculated
using the weight  of  the original  EO
charge and the measured EO emissions
at the  outlet of the control unit.  The
weight  of  EO  originally  charged  to  the
chamber was obtained by multiplying the
weight of 12/88 gas by 0.12. No analysis
was  performed on the sterilant gas  to
verify the EO concentration. A correction
was  made for  the  EO remaining in  the
chamber (WR)  which was determined
using the ideal gas law. The mole fraction
of EO left  in the chamber was  obtained
from samples  taken after Evacuation 7

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either before or after the chamber had
been  refilled. The  recovery  efficiency
(ER) is then given by:

   ER = 100 x(Wc-WR-Wout)/(Wc-WR)    (3)

where Wc  is  the weight of EO originally
charged to the chamber.

Results and Discussion
   The sampling method was evaluated
using a gas cylinder containing known
concentrations of EO and CFC-12. The
gas cylinder was first analyzed  on the
GC. Then  the gas  cylinder was  treated
as a sample  by  installing a tee between
the cylinder and the sampling line. The
flow rate of the  gas out of the cylinder
was adjusted  so that there was  always
excess flow past the tee during sampling.
Response of the cylinder sample through
the sample line was compared  to the
response of  the  cylinder sample
analyzed directly.
   The inlet sampling bias was measured
twice using a 2,508 ppmv EO and 6,022
ppmv  CFC-12  standard.  The  total
sampling and analytical bias  in the EO
measurement ranged  from  0-7% with
an average of 3.5 percent. The sampling
bias in the EO measurement ranged from
0.2 to  11.9% with an  average  of  6
percent. In both  cases the sampling was
biased positively for  EO indicating that
the method would  tend to overestimate
EO emissions. The total  sampling and
analytical  bias   in  the   CFC-12
measurement ranged from 4.3 to 12.5%
with  an average of  8.4  percent. The
sampling  bias   in  the   CFC-12
measurement ranged from 0 to 15.2%
with an average of 7.6 percent.
   The  outlet  sampling  bias  was
measured three times using a 502.4
ppmv  EO and  1,200  ppmv  CFC-12
standard. The  total  sampling and
analytical bias in  EO measurement
ranged  from 1.9  to  12.9% with  an
average of 7.4  percent. The  sampling
bias in the EO measurement ranged from
-7.5  to  7.1% with  an average of  +1.3
percent.  The  total  sampling  and
analytical   bias   in   the   CFC-12
measurement ranged  from  -  9.5  to
4.8% with an average  of -2.4 percent.
The  sampling bias  in the  CFC-I2
measurement averaged  11 percent.
   The analytical method  was evaluated
using a gas  cylinder  containing  known
concentrations of EO and CFC-12. The
gas  cylinder  was analyzed on the GC
using the same procedure as  for the
standard cylinders.  Using the response
of the cylinder sample and the prepared
calibration  curve,  a  measured
concentration of the cylinder sample was
calculated. The measured concentration
was compared to the expected or known
concentration of the gas cylinder.
   The inlet analysis bias was measured
twice using a 2508 ppmv EO and 6022
ppmv CFC-I2 standard.  The analytical
bias in the EO measurement ranged from
-0.2 to -4.4%  with an average of -2.3
percent. In both cases the analytical bias
was negative. The analytical bias in the
CFC-12  measurement  ranged  from
-2.4% to 4.3% with  an average of  1
percent.
   The  outlet  analysis  bias  was
measured three  times using a  502.4
ppmv  EO  and  1200  ppmv CFC-12
standard. The analytical bias in the EO
measurement ranged form 0.3 to 10.1%
with  an average  of 6.2  percent.  In  all
cases  the  analytical  bias  in the  EO
measurement  was  positive.  The
analytical bias in  the CFC-12  mea-
surement ranged from  -5.6 to -18.5%
with  an average  of -12  percent.  In  all
cases the analytical bias in the CFC-12
measurement was  negative,  indicating
that the column may be overloaded  by
the combination of the 2-ml sample size
and the high CFC-12 concentration.
   The  utility  of the   method  in
determining emissions  was evaluated  by
comparing the  measured  EO emissions
for the six empty chamber tests on the
assumption that  the  control device
efficiency did not change with time.

   The expected quantity of EO entering
the control unit  during the six empty
chamber tests  ranged  form 41 to 44 Ib
and averaged 42 Ib, based on 12% of the
total  weight of the 12/88  charge. The
measured quantity  of  EO  entering  the
control unit during these same six tests
ranged from 24 to 62 Ib and averaged 47
Ib. In the one test  where  the measured
weight of EO entering  the scrubber was
24 Ib,  the  inlet sampling pump leaked
during  the first 10  minutes of  the
evacuation  and the  FID  flame  was
extinguished during portions of the third
and  fourth  evacuations.  The two tests
where the  measured weight  of  EO
entering the scrubber  was above 60 Ib
were performed on a day when the EO
standard  calibration  curve  for  inlet
samples  was lower than  on other test
days.
   The  absolute difference  between
measured  emissions  and  expected
emissions was  > 40% for three tests and
was  < 10% for only one test. In five of
the six tests the measured  emissions
were larger than the expected emissions.
   The measured quantity of EO emitted!
to  the atmosphere from the control unit
during the six empty chamber  tests
ranged  from  0.011  to  0.043 Ib  and
averaged 0.022 Ib. The relative standard
deviation (rsd) in  these  six  mea-
surements was twice the  rsd for the inlet
measurements indicating  that  more
variation is associated with the scrubbing
process  than  with  the sterilization
chamber.
   Most of the error in  EO emission
measurement  probably  resulted  from
errors in the  interpolation of the  flow
rate/concentration profile. Ethylene  oxide
emissions were measured with  greater
precision at the scrubber  inlet than at the
scrubber outlet as was expected because
of  the higher concentrations at the inlet.
Part of this  loss of  precision in EO
emission measurement may  be due to
difficulty in identifying the EO  peak in the
chromatogram  because of EO retention
times  that shifted  as  the  EO  con-
centration decreased.
   The  utility  of   the method  in
determining control unit  efficiency  was
evaluated  by  comparing the  measured
throughput efficiencies obtained from the
six empty  chamber tests  on  the
assumption that the control unit efficiency
did not change with time.  All of the
empty chamber tests  were performed on
the same  chamber. The  measured
efficiency  using the throughput  method
with the data from the six  empty chamber
tests ranged from 99.82  to 99.98% and
averaged 94  percent.  The median
efficiency was 99.96  percent. Efficiency
values were above 99.95% in five of the
six tests.  The  one  test in  which the
efficiency was below 99.9%  was where
sampling and  analytical  problems were
encountered as described earlier.
   Comparisons of  the throughput and
recovery efficiencies  were  done  by  a
one-way  analysis of  variance (ANOVA)
with sampling-calculational  procedures
as  a  fixed factor. The interaction term
between the calculational  procedures was
tested to determine if  there was  a
significant effect on   efficiency results
based on the  calculational   procedure
used. A probability  (P)  that  the
calculational method  used has no  effect
was calculated. If P   <  0.05, then the
effect is  taken to be significant. A  one-
way ANOVA resulted  in  a P of 0.86 for
the tests using chambers which did not
contain  product and  0.32 for the tests
using  chambers which did contain
product; therefore, the procedure used to
calculate  the efficiency  does not
significantly  affect the   efficiency
determined.

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  The efficiency results from the tests
where product  was  present  in  the
chamber  were  compared with  the
efficiency  results from  the  tests where
product was not present in the chamber
using a fixed factor ANOVA. A probability
that  the independent variable does not
effect the efficiency was calculated. If P
<  0.05, then the effect was taken to be
significant.  The  ANOVA  calculation
resulted in a P of 0.59 for the interaction
between the calculational procedures; a
P of 0.37 for the interaction  between the
chamber conditions;  and a P of 0.79 for
the  combined  interaction  of  the
calculational  procedure and  chamber
condition.
  Since none of the dependent variables
tested had  a P  s  0.05, there was
significant effect  on  the efficiency
measurement due to  the  presence of
product in  the chamber. Furthermore,
there was no  interaction between the
calculational method  used  and  the
presence or absence of product in the
chamber.  Thus,  the  efficiency  results
were within random  error of the  overall
mean efficiency.
  Several  outlet EO emissions  were
calculated using  the  chamber pressure
and  temperature  data  used to calculate
inlet flow rates. No correction was made
for  the change in the gas  composition
that  occurred  while  the gas was the
scrubber.  The largest change  in  gas
composition  occurs  during  the first
evacuation  when the  gas composition
changes from 30/70  % vol  EO/CFC- 12
entering the scrubber to <1/>99 % vol
EO/CFC-12 exiting  the  scrubber. This
meant that during the  first evacuation
approximately 30% of the moles  of gas
entering the control unit  did not  exit the
control unit. Thus, the  actual flow  rate
coming out of the  control unit was
probably less  than  the flow  rate
calculated by this method. This  method
should over-estimate  EO  emissions,
resulting  in  an under-estimation  of the
control unit efficiency.
  Statistical comparison of data based
on  estimated flows  with data base  on
orifice plate measurements using  a
one-way ANOVA with  flow  calculational
procedures as a fixed factor showed that
the  EO emissions from the scrubber
calculated using orifice plate data were
not  significantly different from  the EO
emissions  estimated using chamber
temperatures and  pressures. The
probability that there was no difference in
the  calculated EO emissions was  0.35; in
the  calculated throughput  efficiencies
0.59;  and  in the  calculated recovery
efficiencies, 0.25. A probability  of 0.05
indicated a significant  difference.  The
calculated efficiencies  were  not
significantly different due to the high
efficiency  of  the  EO  control  unit.
Therefore, in  tests performed on units
that are closed  systems;  therefore,  flow
estimation may be a possible alternative
to orifice plate installation.

Conclusions and
Recommendations
   Six  conclusions  were  based  on the
field   test  results.  First,   the
sampling/analytical  method  adequately
determined the  EO mass flow rate into
the control unit.  Most  of the error
resulted from error in the  interpolation  of
the flow rate/concentration profile.
   Second, the  sampling/analytical
method  adequately determined  EO
emissions at the  outlet of  the dilute  acid
scrubber,  but identification  of the EO
peak  in  the  chromatogram  was
complicated by  EO  retention times that
shifted  as the EO  concentration
decreased. The EO retention  time  shift
was magnified due  to the  large range  of
EO concentrations.  The bias  in  the
sampling/analytical  method averaged
7.4%  for EO and -2.4% for CFC-12.
   Third, the sampling/analytical  method
adequately determined  the efficiency  of
the dilute  acid scrubber.  Measured
efficiency  calculated  by the  throughput
method for empty chamber tests ranged
from  99.82 to  99.98% and  averaged
99.94 percent.
   Fourth,  the   recovery method  of
determining control  unit efficiency  was
comparable to the throughput method  at
this site. Efficiencies calculated  empty
chamber tests by the throughput  method
ranged from  99.82 to  99.98%  and
averaged  99.94 percent. Efficiencies
calculated for empty chamber tests by
the recovery method  ranged from 99.90
to 99.97% and averaged  99.95 percent.
A  one-way  analysis  of  variance
(ANOVA) performed on  the data for the
empty chamber  tests showed that the
methods were not different. The sterilizer
chamber/control unit tested was a closed
system (i.e.  leak-free)  so  this  con-
clusion  may not be  valid at an older
facility where more EO may be lost from
the system as fugitive emissions.
   Fifth, the presence of  product in the
chamber did  not affect  the scrubber
efficiency measurement. The efficiencies
calculated for empty chamber tests by
the throughput  method  ranged  from
99.82 to 99.98% and  averaged 99.94
percent. The efficiencies  calculated  for
full  chamber tests  by the throughput
method  ranged from 99.92 to 99.98%
and averaged 99.96 percent.
  Sixth, EO emissions and control unit
efficiencies calculated using  flow  rates
based on orifice plate data did not differ
significantly for EO emissions and control
unit efficiencies   calculated  using
estimates  based   on  chamber
temperatures and pressures. Ethylene
oxide emissions for empty chamber tests
based on orifice plate data ranged from
0.011 to 0.043 Ib and averaged 0.024 Ib.
Estimated  EO emissions  for the same
tests ranged from 0.006 to 0.036  Ib and
averaged  0.017  Ib.  Throughput
efficiencies based on  orifice plate data
ranged from  99.82  to 99.98% and av-
eraged  99.93 percent.  Throughput
efficiencies based on estimated flows for
the  same  tests ranged  from 99.85 to
99.99%  and averaged 99.95  percent.
Again, the sterilizer chamber/control unit
tested  was  a closed system so  this
conclusion may not  be valid at an older
facility where more EO may be lost from
the  system as fugitive emissions.

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  Joette Steger and  William Gergen  are  with Radian  Corporation, Research
        Triangle Park, NC 27709.
  John H. Margeson is the EPA Project Officer (see below).
  The complete report, entitled  "Sampling/Analytical  Method Evaluation for
        Ethylene Oxide  Emission and  Control Unit  Efficiency  Determinations."
        (Order No.  PB 88-204 235/AS; Cost: $19.95, 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:
            Environmental Monitoring Systems Laboratory
            U.S. Environmental Protection Agency
            Research Triangle Park, NC27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300

EPA/600/S4-88/017
                   080C3Z9   PS
                                                  «GENCI

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