Hydrogen Sulphide

Hydrogen Sulphide (H2S)

Hydrogen sulphide is a colourless, flammable, extremely hazardous gas with a “rotten egg” smell.
It occurs naturally in crude petroleum and natural gas, and can be produced by the breakdown of
organic matter and human/ animal wastes (e.g., sewage). It is heavier than air and can collect in
low-lying and enclosed, poorly ventilated areas such as basements, manholes, sewer lines and
underground telephone/electrical vaults.



Detection by smell

Can be smelled at low levels, but with continuous low level exposure or at higher concentrations you lose your ability to smell the gas even though it is still present.
At high concentrations – your ability to smell the gas can be lost instantly.

Do not depend on your sense of smell for indicating the continuing presence of this gas or for warning of hazardous concentrations.


Heath Impacts

Health impacts can vary with how long, and at what level, someone is exposed. Asthmatics may be at greater risk.

  • Low Concentrations: Irritation of eyes, nose, throat, or respiratory system; effects can be delayed.
  • Moderate Concentrations: More severe eye and respiratory effects, headache, dizziness, nausea, coughing, vomiting and difficulty breathing.
  • High Concentrations: Shock, convulsions, unable to breathe, coma, death; effects can be extremely rapid (within a few breaths).


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