H2S is a gas generated from the processing of crude oil containing sulfur. H2S is generated in conversion units cracking feed stock containing sulfur and from hydrotreaters that specifically focus on removing sulfur by creating H2S.

H2S is highly toxic and generates highly polluting sulfur oxides if burned. Consequently, almost all H2S is extracted in the amine unit and sent to the sulfur plant for conversion into solid elemental sulfur.