In the earth's womb in the composition of gases, there is sometimes hydrogen sulphide - a substance without color and with a sharp, suffocating smell. Hydrogen sulphide is an active substance with a strong corrosion effect. Its removal from the natural gas composition takes place in the purification plants.

Before passing through the gas pipelines, natural gas is also subjected to drying to remove the accompanying quantities of water. Drying takes place in installations where the gas is treated with diethylene glycol.

Since natural gas is colorless and odorless in order to detect its leakage, it is odorized before it is fed into the distribution networks. After purification and drying, 16 g of ethyl mercaptan per 1000 m3 of gas are added.