1.1 This test method covers the determination of total mercury in natural gas at concentrations down to 0.01 (mu)g/m 3 . It includes separate procedures for both sampling and the atomic absorption spectrophotometric determination of mercury. The procedure detects both inorganic and organic forms of mercury. 1.2 The values stated in SI units are to be regarded as the standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.