Question: is sewer gas hydrogen sulfide?
Answer: Hydrogen sulfide (also known as H2S, sewer gas, swamp gas, stink damp, and sour damp) is a colorless gas known for its pungent "rotten egg" odor at low concentrations. It is extremely flammable and highly toxic. Hydrogen sulfide also occurs naturally in sewers, manure pits, well water, oil and gas wells, and volcanoes.