E2658-H2S
Rev 12.03.2021
Hydrogen Sulfide
Colorless toxic, corrosive and flammable gas with a smell of rotten eggs. Occurs in natural
gas, volcanic gases, petroleum, and some sources of well water. It results from the
anaerobic decay of sulfur-containing proteins, e.g. in sewers.
Synonyms: Hydrosulfuric acid, Sewer gas, Sulfuretted hydrogen.
Chemical formula
H
2
S
Molar weight
34
Conversion
1 ppm = 1.40 mg/m
3
Relative gas density (to air)
1.17
Boiling point
−60 °C
Low explosive limit (LEL), % vol.
in air
4.0
Upper explosive limit (UEL), %
vol. in air
44.0
Odor
The characteristic smell of rotten eggs. Above 30 ppm, the odor is
described as sweet or sickeningly sweet.
Odor threshold
0.01-1.5 ppm
Note: Sense of smell becomes rapidly fatigued and can NOT be
relied upon to warn of the continuous presence of H
2
S.
Hazards
Highly flammable, explosive gas.
Broad-spectrum poison, mostly affecting the nervous system. At
low concentrations causes eye irritation, a sore throat and cough,
nausea, shortness of breath, and pulmonary edema. Long-term,
low-level exposure results in fatigue, loss of appetite, headache,
poor memory, irritability, and dizziness. Exposure to high levels
can induce immediate collapse, with loss of breathing and a high
probability of death.
Exposure
limits
(Commission
Directive
2009/161/EU)
TWA
7 mg/mm
3
/ 5 ppm
STEL
14 mg/mm
3
/ 10 ppm
IDLH
(NIOSH)
140 mg/mm
3
/ 100 ppm
Conversion of ppm to mg/m
3
is calculated for 25°C and 1 atm.
3
