**2.3. NORM in natural gas**

Radon is a radioactive noble gas, present in varying level in natural gas in oil and gas forma‐ tions. In the absence of natural gas, radon easily dissolves in the light hydrocarbon. Radon usually follows the gas stream when produced with the oil and gas. If the natural gas is fractionated, higher percentage of radon can concentrate in the propane streams and lower degree in the ethane streams. Most of the radon decay products are found in ambient aerosols, airborne particulates, or surfaces. Most radon progeny are short-lived, with the exception of Po210 and Pb210, which have relatively long half-lives of 138 days and 22.6 years, respectively. Formation of thin radioactive films on the inner surfaces of gas-processing equipments, such as scrubbers, compressors, reflux pumps, control valves, and product lines, due to the release of daughters of radon.
