TITLE
Stability of Air Toxic Gases Listed in Title III Clean Air Act
Amendments

AUTHOR(S)
R.K.M. Jayanty, L.B. Jaffe, J.R. Albritton,  M.D. Jackson and M.R.
Midgett

PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
Research Triangle Park, NC 27709

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

ABSTRACT
     A repository of 59 organic compounds has been established by
the U.S. Environmental Protection Agency (EPA) for use as gas
standards in performance audits during field validation of emission
concentrations from stationary sources.  These compounds are listed
in Title III of the 1990 Clean Air Act Amendment.  The compounds
are prepared in compressed gas cylinders and recyclable aluminum
containers.  Three concentration ranges were selected: low (20 to
200 ppb), mid-level (0.5 to 5 ppm), and high (5 to 50 ppm).  The
recyclable aluminum containers were only prepared in the low range,
and pressures were generally below 400 psig.  The compressed gas
cylinders contained pressures up to 2000 psig. In this program to
ensure that the concentration of each gas standard had not changed,
each standard was analyzed periodically for stability.  The gas
mixtures were analyzed by the manufacturer before shipment.  They
were then analyzed upon receipt, and reanalyzed periodically to
determine any change in concentration.  The stability data obtained
to date indicates that many compounds are stable in the compressed
gas cylinders; however, some of the compounds in the recyclable
containers are not stable.