A HYDROCARBON DETECTOR FOR THE REMOTE-SENSING OF VEHICLE EXHAUST EMISSIONS

A new remote sensor for measuring on-road carbon monoxide, carbon dioxide, and hydrocarbon exhaust emissions in under 1 s from vehicles passing the sensor is described. The new design adds the capability for measuring exhaust hydrocarbons and eliminates the need for liquid-nitrogen-cooled detectors while improving upon the overall signal to noise. Under typical field operating conditions, sensitivity to 0.05% propane with a precision of 0.014% propane is observed. Two types of water interferences important to the measurement of exhaust hydrocarbons are reported. The water vapor present in all auto exhaust causes a small positive bias dependent on the analytical wavelength chosen. A much larger interference is caused by liquid water (often called "steam") plumes seen behind cold vehicles at low temperatures. © 1995 American Institute of Physics.