AS 4670:2018 Commercial propane and commercial butane for heating purposes
A.2  Radioactivity
Sources of commercial propane and commercial butane (natural gas and crude oil) may contain radioactive substances such as radon. Processing of these sources may increase the concentration of radioactive components in the final product.
Radon-222 ( 222 Rn) has a half-life of 3.8 days and quickly decays, via a series of short lived isotopes, to the radioactive isotope lead-210 ( 210 Pb), which has a relatively long half-life of 22 years. Where vapour is drawn off and the storage vessel (tank) is successively refilled with liquid product over an extended period this could result in a build-up of lead ( 210 Pb) within the storage vessel.
Radon from fuel gases is generally not of any concern to the consumer, because the indoor concentrations from these sources are much lower than the levels that typically result from other sources; ground emissions and building materials in particular. It is again not envisaged, nor ever recorded, that lead ( 210 Pb) presents any danger to the consumer as this material is not only low in concentration, it is also more prone to coat the inside of containers and pipes and to concentrate in powdery residues that collect in the bottom of tanks and cylinders.
The areas of concern when dealing with potential lead ( 210 Pb) contamination are the tanks that are large enough to be fitted with access panels. When inspecting these pressure vessels, the hazard assessment and developed controls need to account for the hazard posed by radioactive dust. Where selected controls include personal protective equipment, this should include respiratory protection, either supplied air respirators or powered respirators. Samples of the residue taken from the tank should be analysed for their lead ( 210 Pb) content and the residue disposed of according to the prevailing regulations.
Advice should be sought from the local radiological authorities. The recommended maximum concentration of radon in natural gas in AS 4564 is 600 Bq/m 3 . However, because of the usage pattern of LP Gas (storage) and the 3.8-day half-life of radon, it is not practicable to specify a radon level for LP Gas in a manner analogous to that of flowing natural gas. Attempts to correlate the level of lead ( 210 Pb) in residual material taken from tanks during cleaning, with the service history and radon concentrations in the feed natural gas used to produce commercial propane have proven unsuccessful.