What is sour gas?
Sour gas is natural gas that contains measurable amounts of hydrogen sulphide (H
2
S), a colourless substance that is poisonous to humans and animals. Also known as hydrosulphuric acid, sewer gas, and stink damp, it is recognizable by its rotten egg smell at very low concentrations (0.01 – 0.3 parts per million). Exposure at higher concentrations of H
2
S affects a person's sense of smell and, as a result, there is no perceptible odour. Exposure to high concentrations of H
2
S (150 - 750 parts per million) can cause a loss of consciousness and possible death.
Effects of hydrogen sulphide (H
2
S) on people
| Parts per million (approximate ranges) |
| 0.01-0.3 | Odour is detectable |
| 1-10 | Moderate to strong odour. People may experience nausea, tearing of the eyes, headaches and loss of sleep following prolonged exposure. The effects appear to be reversible and not serious for the general population, although more susceptible individuals may respond more severely. |
| 10-150 | Increasing degree of irritation to eyes and lungs. |
| 150-750 | Severe health effects which may lead to death, become more likely as concentration and exposure time increase. |
| greater than 750 | Death may occur in minutes or less. |
In addition to existing in natural gas, H
2
S can be found in sour crude oil, sulphur hot springs, sewage, swamps, manure piles in stockyards, landfills, and the holds of fishing ships, as well as in the processing of leather, pulp and paper, and rayon textiles.
Sour gas deposits are found in several regions throughout Alberta, with the majority in central and western Alberta.
How is sour gas formed?
Hydrogen sulphide occurs naturally in crude petroleum, volcanic gases, and hot springs. It can also form when organic materials, such as plants or human and animal wastes decompose in an oxygen-free environment, a process known as anaerobic decomposition. This process can occur in sewers, manure piles, swamps, and composts.
