Hydrogen Sulfide (H2S)
Hydrogen sulfide is a toxic, flammable gas that forms when organic material breaks down. It smells like rotten eggs at low levels, but at dangerous levels it knocks out your sense of smell, so you may think it’s gone.
- Oil & Gas
- Utilities
- General Industry
Where it’s found
- Sewers, manholes, lift stations and wastewater treatment plants
- Oil and gas wells, tanks and pipelines (“sour” gas and crude)
- Pulp and paper mills, tanneries, refineries
- Manure pits, swamps and landfills
Health effects
- Low levels: eye and throat irritation, headache, nausea.
- Around 100 ppm: loss of smell. This is immediately dangerous to life and health.
- High levels: rapid collapse, stopped breathing and death, sometimes after one or two breaths.
It’s heavier than air and collects in low areas, pits and confined spaces.
Protect yourself
- Get H2S awareness training before working where it may be present.
- Wear a personal H2S monitor and know its alarm levels.
- Test the air before entering pits, tanks and confined spaces. See Confined Spaces.
- Know the wind direction and your escape route (upwind and uphill).
- Use supplied-air respirators or SCBA where levels may be high.
Never attempt a rescue without supplied air. Many H2S deaths are coworkers who went in to help. Call for trained rescuers.
Standards & references
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