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MOBILE SOURCE NOX MONITOR, HYDROGEN-ATOM DIRECT CHEMILUMINESCENCE METHOD
Citation:
Fontijn, A., H. Volltrauer, AND W. Frenchu. MOBILE SOURCE NOX MONITOR, HYDROGEN-ATOM DIRECT CHEMILUMINESCENCE METHOD. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-79/120.
Description:
An analyzer was developed for measuring motor vehicle NOx (NO and NO2) emissions based on the chemiluminescence reaction of NO and NO2 with hydrogen atoms. This eliminated the need for an NO2 to NO converter as required with ozone chemiluminescence for NOx analysis. The hydrogen-atom source is based on the thermal dissociation of molecular hydrogen on a hot (approximately 1900C) tungsten filament. The unit has linear response to NOx over a concentration range from 4 ppm to greater than 3000 ppm. No interferences were observed with H2O, CO, CO2, toluene, isopentane, NH3, HCN, CH3NH2, or H2 at concentrations encountered in raw automobile exhaust. Oxygen and ethylene caused minor interferences which should be inconsequential in actual application.