Hydrogen sulphide gas, also known as sewer gas, is the result of bacterial breakdown of organic material, such as human and animal waste. It can also result from industrial processes, such as food processing, leather tanning and the refinement of petroleum. Low-level exposure to sewer gas can make you sick and high-level exposure can kill you.

Hydrogen sulphide is a colourless, flammable gas. At low levels, it smells like rotten eggs. At high levels, it quickly destroys the sense of smell, so victims may no longer recognise an odour.

Symptoms of low-level exposure to sewer gas include extreme fatigue, dizziness, headaches, irritability and memory loss. Runny eyes and a runny nose are also common.

Exposure to high levels of sewer gas can lead to a loss of consciousness, coma, seizures and even death. The level exposure necessary to create these symptoms is rarely possible in a home. It is almost always related to an industrial setting.

In some cases, victims may experience central nervous stimulation after exposure to sewer gas. Symptoms include excitation, rapid breathing and headaches.

In the home, most exposure is the result of faulty plumbing. Dry traps allow sewer gas to enter a home. Flush unused traps with water weekly. When doing plumbing repairs, stuff a damp rag in open drain pipes to prevent sewer gas from entering the house.