scope:

This Standard sets out a method for determining methane and non-methane organic compounds in ambient air using a direct-reading instrument. The method applies to the determination of hydrocarbons in ambient air within the concentration range 0 to 20 p.p.m.C. by volume.

The methane and non-methane organic compound content of the air is most commonly measured using an automatic or intermittent sampling direct-reading instrument containing a flame ionization detector (FID) and the results obtained are reported as a methane equivalent response. The analysis is sensitive to all hydrocarbons, but will also respond to almost all organic compounds and will yield responses more or less depending on the number of carbon to hydrogen bonds in the compound. Empirical data generally show that the relative sensitivity to various hydrocarbons is approximately equal on a carbon mass basis. Unsaturated, oxygenated and halogenated compounds give a lower response.