TABLE 11.1 Reference and Equivalent Methods Designated by the U.S. Environmental Protection Agency for Monitoring Criteria Gaseous Air Pollutants

Gas Reference or equivalent method

N02 Ozone chemiluminescence

Differential optical absorption spectrometry Sodium arsenite

03 UV absorption

Chemiluminescence Differential optical absorption spectrometry

CO Nondispersive infrared

S02 UV fluorescence

Differential optical absorption spectrometry Pararosaniline

The principles behind these and other techniques used to measure a variety of trace gases in the atmosphere, including the criteria pollutants and free radicals such as N03, OH, H02, and R02, are described in the following sections. In addition, typical tropospheric concentrations in regions from remote to urban areas are given.

In the second section of this chapter, techniques for measuring and characterizing particles are described.

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