* H2S Occurs and we can found naturally in nature in areas like, Oil Fields, Mine, Volcanoes, produced through decay of organic matter industries like, Fishing industry, Tanneries, Manure Processing.
* The largest industrial route to H2S occurs in petroleum refineries. The hydro desulfurization process liberates sulfur from petroleum by the action of hydrogen.
* During of extraction, hydrogen sulfide may be released into the atmosphere at wellheads, pumps, piping, separation devices, oil storage tanks, water storage vessels, and during flaring operations.
* It is naturally occurring chemical produced by bacteria as it decomposes organic material and created by natural biological processes or by human activity.
http://www.ask-ehs.com/safety-training/h2s/
