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AMBIENT AIR NON-METHANE HYDROCARBON MONITOR
Citation:
Burch, D. AMBIENT AIR NON-METHANE HYDROCARBON MONITOR. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-80/201.
Description:
A monitor has been developed with adequate sensitivity and accuracy to measure continuously the concentration of non-methane hydrocarbons (NMHC) in ambient air. The monitor consists of pump and manifold system along with two basic instruments, a methane monitor and a flame-ionization detector (FID). The methane monitor, which employs gas-filter correlation techniques, makes use of the infrared absorption characteristics of methane to measure its concentration. A slight interference in the measurement of methane by H2O vapor in the sample air is accounted for from the simultaneous measurement of the H2O concentration. The flame-ionization detector measures the concentration of the total hydrocarbons (THC), including methane. The concentration of non-methane hydrocarbons is found by subtracting the methane concentration from the THC concentration. The noise-equivalent concentrations (peak-to-peak) of the methane monitor and the FID are approximately 50 ppb and 5 ppb of carbon, respectively. The estimated uncertainty in the measurement of a typical low-level NMHC concentration is between 20 ppb and 50 ppb. Concentrations as high as approximately 70 ppm can be measured.