Gas distribution companies worldwide are required to survey their networks on a periodic basis. Depending on the country and type of gas, this can range from every six months to every three years, or longer. Additionally, new safety regulations in Europe put gas companies under an increasing obligation to guarantee traceability of their surveys by providing precise location and dating of gas concentrations measured. Systematic leak detection is therefore part of the overall safety policy of gas distribution companies. Planned periodic detection programs also allow gas companies to understand their network conditions and to define economical maintenance, equipment and systems renewal policies. Aimed at the early identification of any network deterioration, systematic leak detection enables timely remedial action. As such, network leak surveys are part of any maintenance policy with the dual aim of increasing safety and maximizing efficiency. The main goals of gas leak detection are to identify potential gas leaks, confirm actual leaks and select those leaks that represent a threat to public safety and therefore require immediate repairs. Leak detection also strives to detect leaks at an early stage and prevent gas concentrations in air reaching the lower explosive limit (LEL) of 4.4% volume gas in air or 44 000 parts per million (ppm). At that level, the gas (usually methane) will ignite in the presence of a spark or flame.

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