United States
Environmental Protection
Agency
Environmental Monitoring Systems «.
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S4-81-029 July 1981
Project Summary
A Summary of the EPA
National Source Performance
Audit Program - 1979
R. G. Fuerst, E. W. Streib and M. R. Midgett
A national quality assurance audit
program for methods used in
stationary source tests was conducted
in 1979 by the Quality Assurance
Division of the Environmental
Monitoring Systems Laboratory, U.S.
Environmental Protection Agency,
Research Triangle Park, North
Carolina. In this program, quality
assurance materials were sent to
interested participants for the
measurement of a gas volume
(Method 5, dry gas meter only) or the
analysis of liquid samples simulating
collected sulfur dioxide and nitrogen
oxides (Methods 6 and 7, respective-
ly). Each participant returned the
analytical results to the Source
Branch, Quality Assurance Division,
for evaluation. An individual report
was returned to each participant after
processing.
The Project Report summarizes the
audit results of 1979 for those three
source test methods.
Thisf Project Summary was
developed by EPA's Environmental
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
One of the fundamental responsibil-
ities of laboratory management is the
establishment of a continuing program
to insure the reliability and validity of
generated data. This is accomplished by
a strong quality assurance program.
To assist in this type of program, the
Environmental Monitoring Systems
Laboratory (EMSL) of EPA in 1977
established a nationwide performance
audit program to insure that source
emission data collected for compliance
determination purposes are accurate
and reliable. This program had three
main purposes:
• to verify that the analytical and
computational parts of the specific
reference methods were being
proerly used,
properly used,
• to assist wherever possible to
improve the quality of the meas-
urement being made,
• to aid the participating labora-
tories in assessing their analytical
performance relative to that of
other laboratories conducting
similar analyses.
These goals were realized by sending
specific performance materials to
interested laboratories for analysis.
EPA's National Quality Assurance
Audit Program for Stationary Source
Test Methods was conducted in the
spring and fall of 1979. The methods
examined were Methods (dry gas meter
only), Method 6 (S02) and Method 7
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(NOx). The audits were conducted by the
Quality Assurance Division (QAD) of
EPA's Environmental Monitoring
Systems Laboratory located at Research
Triangle Park, North Carolina. They
involved laboratories from industry,
contracting firms, universities, foreign
countries, and governmental agencies.
Audit Participants
Invitations to participate in the
semiannual source audit program for
spring and fall of 1979 were sent to all
volunteers who had previously
participated in the audit program. Other
laboratories were added to the master
list through their direct contact with the
Source Branch, QAD, or the Regional
Quality Control Coordinator (RQCC).
Audit Materials
To provide a check on the calibration
of the dry gas meter used in the Method
5 stack sampling train, a critical orifice
device was developed to pass a certain
flow rate of air through the dry gas
meter when the measured vacuum on
the orifice was at least 16 inches of
mercury. This device allows an analyst
to compare a volume measured at his
location with one measured at an EPA
location. Volumes measured at both
locations are compared to the original
calibration of the device, compensated
for the effect of ambient temperature
and pressure on the measurement at
both locations.
For the audits of Methods 6 and 7, five
different concentration levels of
simulated source sulfur dioxide (SO2)
and nitrogen oxides (NOx) samples were
prepared. These solutions enabled the
participants to analyze and calculate
different concentration levels of SO 2
and NOx, using Methods 6 and 7. The
true values of these samples were
based on theoretical concentrations
calculated from gravimetric
preparations and certain assumed
volume measurements.
Results
A summary of the Method 5 data
shows that an average of 77% of the
247 laboratories that requested
samples returned data for the spring
and fall studies. Comparing the reported
results from these laboratories to the
2% Federal Register specification for dry
gas meter accuracy, we find that in
Audit 0379, 34% of the laboratories
came within 2% of the EPA value, while
in Audit 0879, 43% of the laboratories
were able to do so.
A summary of Method 6 data shows
an average of 72% of the 244
laboratories requesting samples
returned data for the spring and fall
studies. Of those laboratories reporting
data, 50% of the laboratories came
within an average of 1.7% of the EPA
value for Audit 0379. For Audit 0979
they came within 2.1%.
A summary of Method 7 data shows
an average of 64% of the 203
laboratories requesting samples
returned data for the spring and fall
audits. Of those laboratories returning
data 50% were able to come within an
average of 7.8% of the EPA value for
Audit 0379, while in Audit 1079 they
came within 7.0%.
To examine previous audit data for
trends, a certain degree of accuracy was
chosen and plotted for each method.
They were: 2% accuracy for Methods 5
and 6, and 5% accuracy for Method 7.
Use was made throughout this reporIB
of an outlier test (Chauvenet's Criterion)
to determine the values that lie outside
the bulk of the collected data.
Recommendations
To create a sample repository, the
Quality Assurance Division of the
Environmental Monitoring Systems
Laboratory intentionally produced an
over-supply of samples for the audits of
EPA Methods 6 and 7 discussed in this
report. These stable samples are
available to any laboratory having a
legitimate need for them, such as
training new analysts and conducting
periodic external quality control checks
of the laboratory. Included with these
practice samples is a statement of true
concentration with no requirement for
return of data to EPA. We recommend
that all participants make use of this
sample repository, to increase their
overall analytical skills with typical
Methods 6 and 7 samples.
I
The EPA authors R. G. Fuerst, E. W. Streib, and M. R. Midgett are with the
Environmental Monitoring Systems Laboratory, Research Triangle Park, NC
27711.
R. G. Fuerst is the EPA Project Officer (see below).
The complete report, entitled "A Summary of the EPA National Source Perform-
ance A udit Program - 1979." (Order No. PB 81-199 366; Cost: $8.00, 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. NC 27711
* US GOVERNMENT PRINTING OFFICE; 1«81-757-012/7161
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