Natural gas odorization is an important safety measure, not just for gas purchasers and customers. Formerly used city or cokery gases had a strong intrinsic odor and rarely required odorization. Meanwhile, the commonly used natural gas is cleaned and almost odorless. In order to be able to immediately detect leakage in the gas network, the natural gas odorization is mandatory as a safety measure. The gases added during the odorization generate specific warning odors. This prevents the formation of explosive gas/air mixtures, which are highly dangerous.
The odorants used in the odorization of natural gas must fulfill special safety requirements. Their odor must be perceptible even at a high dilution, and unmistakably induce the association with gas leakage. The odorant must therefore smell unpleasant and distinctive.
In Germany, volatile organic sulfur compounds are frequently used as odorant. Their typical savor is evocative of the smell of rotten eggs. Often the odorless saturated sulfur heterocycle tetrahydrothiophene (THT) is used in concentrations of 12 to 25 mg/m³. Frequently, also mercaptan mixtures are in use.
There are also odorants free of sulfur. Unlike the odorization with the sulfur-containing substances THT or Mercaptan, sulfur-free odorants have the advantage that no additional sulfur oxides are formed during the combustion of natural gas. Examples of sulfur-free odorants are mixtures of ethyl acrylate (> 50%), methyl acrylate and 2-ethyl-3-methylpyrazine. These substances produce a solvent-like odor which, according to a study by the DVGW, is still associated with natural gas by operators. But, the effectiveness of these substances is still controversial.
(Source: Wikipedia.de, "Odorierung", 10/2016).
