Page 258 - Fundamentals of Air Pollution

II. Mobile Monitoring and Surveillance 219

Fig. 15-1. California South Coast Air Basin stationary monitoring locations operating
during 1991. (L.A., Los Angeles). Source: California Air Resources Board, "Summary of 1991
Air Quality Data, Gaseous and Particulate Pollutants," Vol. 23, 1991.

and stationary fixed monitors. The major disadvantage is the sparsity of
suitable instrumentation that operates properly in the mobile platform envi-
ronment. Limitations of existing instrumentation for use on movable plat-
forms are inadequate temperature and pressure compensation; incompati-
ble power, size, and weight requirements; and excessive response time.
Most movable platforms are helicopters, airplanes, trucks, or vans. These
platforms do not provide the relatively constant-temperature environment
required by most air quality instrumentation. Equipment mounted in air-
craft is subject to large pressure variations with changing altitude. Most
instrumentation is designed to operate with alternating current (AC) electri-
cal power, whereas relatively low amounts of direct current (DC) power
are available in aircraft or vans. Space is at a premium, and response times