Hydrogen sulfide

Agent Name
Hydrogen sulfide
CAS Number
Major Category
Toxic Gases & Vapors
Acide sulfhydrique [French]; Acide sulphhydrique; Dihydrogen monosulfide; Dihydrogen sulfide; Hydrogen sulfide; Hydrogen sulfide (H2S); Hydrogen sulfure [French]; Hydrogen sulfuric acid; Hydrogen sulphide; Hydrogene sulfure [French]; Hydrogene sulphure; Hydrosulfuric acid; Idrogeno solforato [Italian]; Schwefelwasserstoff [German]; Sewer gas; Siarkowodor [Polish]; Stink DAMP; Sulfur hydride; Sulfureted hydrogen; Zwavelwaterstof [Dutch]; [ChemIDplus] UN1053
Chemical Asphyxiants
Colorless gas with a strong odor of rotten eggs; Note: Sense of smell becomes rapidly fatigued & can NOT be relied upon to warn of the continuous presence of H2S; Shipped as a liquefied compressed gas; [NIOSH]
"Hydrogen sulfide is produced naturally by decaying organic matter and is released from sewage sludge, liquid manure, sulfur hot springs, and natural gas. It is a byproduct of many industrial processes including petroleum refining, tanning, mining, wood pulp processing, rayon manufacturing, sugar beet processing, and hot asphalt paving. Hydrogen sulfide is used to produce elemental sulfur, sulfuric acid, and heavy water for nuclear reactors." [ATSDR Medical Management]
"CNS injury is immediate and significant after exposure to hydrogen sulfide. At high concentrations, only a few breaths can lead to immediate loss of consciousness, coma, respiratory paralysis, seizures, and death. . . . Hydrogen sulfide is a mucous membrane and respiratory tract irritant; pulmonary edema, which may be immediate or delayed, can occur after exposure to high concentrations." [ATSDR Medical Management] Like cyanide, causes cellular asphyxiation; Also a mucous membrane irritant; IDLH = 100 ppm; Pulmonary edema at 300-500 ppm; Rapidly fatal at 600-800 ppm; [Olson, p. 271] H2S is heavier than air; it displaces air in confined spaces. 80 fatalities were recorded by OSHA from 1984-94. Prevent deaths by using H2S detection equipment, air-supplied respirators, and confined space safety training. [Fuller DC, Suruda AJ. J Occup Environ Med. 2000;42:939-942] Possible frostbite from contact with liquid; [NIOSH] The following chemicals can release H2S when spilled in water: Sulfur chlorides; Phosphorus pentasulfide; and Sodium, Potassium, Calcium & Zinc hydrosulfite. [ERG 2016] "Measuring thiosulfate in urine allows health care providers to identify nonfatal H2S exposure, allowing life-saving prevention opportunities. Measuring thiosulfate in blood is the preferred method to confirm death from H2S exposure." [PMID 24164756] See the Process, "Toxic Gas from Spilling Chemical in Water." Hydrogen sulfide is fibrogenic to the lungs in the context of an acute inhalation exposure complicated by bronchiolitis obliterans.
Biomedical References

Exposure Assessment

Skin Designation (ACGIH)
Insufficient data
1 ppm
5 ppm
Ceiling(OSHA) = 20 ppm, 50 ppm (for 10-min peak once per 8-hr shift)
5 ppm
100 ppm
Excerpts from Documentation for IDLHs
It has been reported that 170 to 300 ppm is the maximum concentration that can be endured for 1 hour without serious consequences [Henderson and Haggard 1943] and that olfactory fatigue occurs at 100 ppm [Poda 1966]. It has also been reported that 50 to 100 ppm causes mild conjunctivitis and respiratory irritation after 1 hour; 500 to 700 ppm may be dangerous in 0.5 to 1 hour; 700 to 1,000 ppm results in rapid unconsciousness, cessation of respiration, and death; and 1,000 to 2,000 ppm results in unconsciousness, cessation of respiration, and death in a few minutes [Yant 1930].
Odor Threshold Low
0.001 ppm
Odor Threshold High
0.13 ppm
Lethal Concentration
LC50 (mice) = 634 ppm/1H
Explanatory Notes
Detection odor threshold from AIHA (mean = 0.0094); Flash point = 500 deg F;
burn readily
0.1 ppm
30 ppm
100 ppm

Adverse Effects

Toxic Pneumonitis
Other Poison
Chemical Asphyxiant

Diseases, Processes, and Activities Linked to This Agent


Occupational diseases associated with exposure to this agent:


Activities with risk of exposure: