Hydrogen sulfide, also known as H2S, is produced by the anaerobic decomposition of organic sulfur bearing materials. These may be related to natural gas, petroleum, wastewater sludge, pulping liquors and other organic materials. Hydrogen Sulfide is a colorless, toxic and flammable gas that is dangerous at extremely low levels. This dangerous gas is associated with oil production, refining activities, wastewater collection and treatment systems, wood pulping operations and entries into confined spaces.
29 CFR 1910.119, 1910.120, 1910.132, 1910.134, 1910.146 & The General Duty Clause NIOSH Recommendations