For an alternative meaning for H₂S, see H2S radar.

The chemical compound hydrogen sulfide (Hydrogen sulphide in British English) H₂S is a sulfide compound that has an unpleasant smell; it is responsible for the smell of rotten eggs. This gas can suffocate sewer workers and is often associated with other decay smells in swamps. Hydrogen sulfide is produced by the breakdown of sulfur-containing proteins and is responsible for much of the foul odor of feces and flatulence.

Hydrogen sulfide occurs naturally in crude petroleum, natural gas, volcanic gases, and hot springs. It can also result from bacterial breakdown of organic matter. It is also produced by human and animal wastes.

Hydrogen sulfide can also result from industrial activities, such as food processing, sewage treatment, coke ovens, paper mills, tanneries, and petroleum refineries..

It is an acidic gas which reacts with alkali and metals such as silver. This is the reason why silver jewellery turns black when exposed to polluted atmosphere for a long duration. The silver sulfide resulting from the reaction is black in colour.

Health effects

Hydrogen sulfide is considered a broad-spectrum poison, meaning it can poison several different systems in the body. Breathing high levels of hydrogen sulfide may kill the olfactory nerve (making it impossible to smell the gas) and can cause death within just a few breaths. There could be loss of consciousness after one or more breaths.

Exposure to lower concentrations can result in eye irritation, a sore throat and cough, shortness of breath, and fluid in the lungs. These symptoms usually go away in a few weeks. Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness.

Animal studies showed that pigs that ate food containing hydrogen sulfide had diarrhea after a few days and weight loss after about 105 days.