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DEVELOPMENT OF A MONITOR FOR HCN IN MOBILE SOURCE EMISSIONS
Citation:
Burch, D., P. Davila, F. Gates, AND J. Pembrook. DEVELOPMENT OF A MONITOR FOR HCN IN MOBILE SOURCE EMISSIONS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-79/113.
Description:
Three real-time monitors for measurement of HCN concentrations in mobile source emissions have been designed, built, tested, and delivered to the Environmental Protection Agency (EPA). The important design parameters for these identical instruments were determined during the first phase of the program of performing tests with a versatile gas-filter correlation spectrometer built previously in our laboratory for EPA. The instruments employ a gas-filter cell to provide sensitivity to HCN while discriminating against other infrared active gases such as H2O, CO2, NH3 and many hydrocarbons that occur in mobile source emissions. These gases absorb near 3 micrometers, the approximate center of the narrow spectral band employed by the instrument. Samples are contained in a temperature-controlled cell that uses a 20-pass optical system with an optical path length of 15.5 m. An H2O monitor built as an integral part of the instrument measures the H2O concentration, making it possible to account for a small amount of interference by this gas in the sample. The rms noise-equivalent-concentration of HCN is less than 0.02 ppm. The combined error after accounting for H2O interference for most dilute samples is less than 0.1 ppm HCN.