Hydrogen sulfide is of two types: (1) atmospheric; and (2) soluble (dissolved in water).
The limit: The King County limit for atmospheric hydrogen sulfide is 10 parts-per-million-volume (ppmv) measured at a designated monitoring manhole. King County also may restrict discharges of soluble sulfide on a case-by-case basis.
King County may restrict discharges of soluble sulfide on a case-by-case basis. For guidance, King County has a screening limit of 0.1 mg/liter.
About hydrogen sulfide
Hydrogen sulfide gas can be dangerous to breathe and presents serious odor problems (the smell of rotten eggs). It also reacts with water to form sulfuric acid, which corrodes sewer lines.
Sewer pipes may be destroyed by corrosion caused by sulfuric acid.