hydrogen sulfide

type of colorless flammable and poisonous gas

Hydrogen sulfide (hydrogen sulphide in British English) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs and flatulence. It often results from the bacterial break down of organic matter in the absence of oxygen, such as in swamps and sewers (anaerobic digestion). It also occurs in volcanic gases, natural gas and some well waters. The odor of H2S is commonly misattributed to elemental sulfur, which is in fact odorless. Hydrogen sulfide has numerous names, some of which are archaic (see Table).
See more at Wikipedia.org...

Noun
1. a sulfide having the unpleasant smell of rotten eggs
(hypernym) sulfide, sulphide

Gas emitted during organic decomposition. Also a by-product of oil refining and burning. Smells like rotten eggs and, in heavy concentration, can kill or cause illness.

A flammable, colorless gaseous compound of Hydrogen and Sulfur (H2S) , which in small amounts has the odor of rotten eggs. Sometimes found in Petroleum, it causes the foul smell of Petroleum fractions. In dangerous concentrations, it is extremely corrosive and poisonous, causing damage to skin, eyes, breathing passages, and lungs and attacking and paralyzing the nervous system, particularly that part controlling the lungs and heart. In large amounts, it deadens the sense of smell. Also called : Hepatic Gas of Sulfureted Hydrogen