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Hydrogen sulfide, commonly known as H2S, is a toxic and extremely hazardous compound.

Occurring naturally in coal pits, sulfur springs, and gas wells, H2S is a particular hazard in oilfield environments. The hazard extends even to core samples taken for laboratory analysis.

In terms of working alone and worker protection plans, the possible presence of H2S radically changes safety management programs.

That "Rotten Egg Smell" and H2S

At low concentrations - well under 1 part per million (ppm) - H2S is detected by a strong rotten egg odor.

Around 30 ppm to 100 ppm, hydrogen sulfide can have a sickly sweet odor.

However, hydrogen sulfide in concentrations over 100 ppm causes rapid paralysis of the olfactory nerves and is therefore not detectable by odor. This means H2S is undetectable by smell at killing concentrations.

Exposure

Exposure to H2S blocks cellular oxygen similar to carbon monoxide. Exposure results in these effects:

  1 - 10 ppm - Irritation of eyes, nose and throat

  10 - 50 ppm - Headache, dizziness, coughing, shortness of breath, nausea, and vomiting

  50 - 200 ppm - Coma, convulsions, biological shock, severe respiratory distress and possible death

Characteristics

Hydrogen sulfide is 20% heavier than air. This means H2S will collect in low areas and in confined spaces.

H2S exposure often results in multiple deaths because unprotected co-workers cannot safely rescue victims. Without protection, rescuers can easily succumb to the same environmental conditions that took their co-workers.