TITLE
Evaluation of Precision of EPA Methods 3A, 6C, and 7E

AUTHOR(S)
Thomas J. Logan, Wayne E. Reynolds, W. Cary Eaton, Elliot Lieberman

PERFORMING ORGANIZATION NAME AND ADDRESS
W. Cary Eaton
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, NC 27709

SPONSORING AGENCY NAME AND ADDRESS
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711

ABSTRACT
The U.S. EPA sponsored a study to estimate the precision
(repeatability and reproducibility) and systematic error of EPA
Test Methods 3A, 6C, and 7E.  These are instrumental methods for
concentration determinations of diluent gases (oxygen [O2] and
carbon dioxide [CO2]), sulfur dioxide (SO2), and nitrogen oxides
(NOx).  The four-laboratory collaborative study was conducted at a
500-megawatt, coal-fired power plant.  Reproducibility estimates,
based on relative standard deviation (RSD), from simultaneous stack
gas measurements by the four test laboratories were approximately
1 1/2% for SO2 measurements and approximately 3% for NOx and oxygen
(O2).  Reproducibility and repeatability estimates from
measurements of audit gases were all equal to or less than 1 1/2%
RSD.  Average systematic errors for individual labs, relative to
NIST traceable audit gases, were all less than 3%.  Systematic
errors are approximately the same as the expected accuracy of
calibration gases.