Federal regulations (49 CFR Part 192.625) state: “A combustible gas in a distribution line must contain a natural odorant or be odorized so that at a concentration in air of one-fifth of the lower explosive limit, the gas is readily detectable by a person with a normal sense of smell.” These regulations state further that “each operator shall conduct periodic sampling of combustible gases to assure the proper concentration of odorant in accordance with this section.” Additionally, a number of states have enacted legislation that requires natural gas to be odorized so that it is detectable at concentrations less than one fifth of the lower explosive limit. See note Note 1. While regulations do not specify the exact method for determining compliance, it has been documented that compliance testing must be olfactory in nature.

Note 1—For example, Massachusetts Section 192.625 MFS Standards requires that “... a concentration of fifteen hundredths of one percent gas in the air is readily perceptible to the normal or average olfactory senses of a person ... .”

These test methods cover procedures to measure the odor level of natural gas by way of olfactory determination. No direct correlation may be ascertained between these test methods and those methods available or under development that quantitatively measure the concentration of sulfur compounds in natural gas.

These test methods outline general procedures to measure the odor detection levels of natural gas. It is the responsibility of persons using these test methods to develop and maintain equipment and specific operating procedures to ensure public safety and compliance with all appropriate regulations.

1.1 These test methods cover the procedures for determining the odor intensity of natural gas through the use of instruments that dilute and mix the sampled natural gas with air. The mixed gas stream is then sniffed by the operator for the purpose of determining the threshold detection level or the readily detection level, or both, for odorant in the natural gas stream.

1.2 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.