Hydrogen Sulfide

Hydrogen sulfide (H₂S) is a colourless, chalcogen hydride gas with a pungent odor like rotten eggs. It is a highly corrosive, flammable and toxic gas and is also a potent neurotoxin.
This gas is formed due to microbial breakdown of organic substances in the absence of oxygen. This gas is mainly used in textile industry and some other industrial sectors.
This gas is found in the atmosphere in swampy areas, volcanic and natural gases, unrefined petroleum and some sources of wells or hot springs. The human body also produces small amounts of hydrogen sulfide, which is used as a signaling molecule.
High concentration of this gas in the human body can cause difficulty in breathing, unconsciousness, organ damage and even death. This gas is denser and heavier than air, but it is soluble in water.