Hydrogen Sulphide (H2S)
Hydrogen sulphide is formed during anaerobic digestion processes and the hydrodesulphurisation of petroleum. H2S is a colourless, toxic gas with an intense stench of rotten eggs. It is extremely flammable and forms explosive mixtures with air.
Ammonia is produced, inter alia, in the decay of animal excrement. It is a colourless, toxic gas with a characteristic pungent smell. It has a low flammability and is very soluble in water. The aqueous solution reacts alkaline.