Laser photoacoustic spectrometer for remote monitoring of atmospheric pollutants.

An acoustically resonant CO(2) laser photoacoustic (PA) spectrometer for remote or in situ monitoring of air pollutants has been designed. The salient features of this PA system, along with the optimization tests of various operating parameters that affect the PA signal (buffer-gas pressure, type of buffer gas, laser power, gas concentration, and acoustic modes), are described. The system has been applied for the detection of pollutants emitted from the exhaust of a car located at a remote distance. Also, an alarm system based on the PA detection technique has been built for leak detection of toxic gases at industrial complexes. The minimum detectable concentration of C(2) H(4) and SO(2) with this system is 50 parts in 10(12) by volume and 50 parts in 10(9) by volume, respectively.