Sewer gas is a mixture of various gases that can form when household waste or other waste decomposes. Some of the gases that typically make up sewer gas, such as ammonia and hydrogen sulfide, are dangerously toxic. Sewer gas can accumulate in septic tanks, municipal sewers, and manure tanks. Sometimes, it can leak into the home through blocked or leaking drains, vents, and sewage pipes. When sewer gas contaminates the inside air of a home, it can present a number of health risks, and can even be fatal in large amounts.
The mixture of gases commonly known as sewer gas is usually a by-product of industrial or human waste decay. Hydrogen sulfide and ammonia may be the most toxic gases present in any given sewer area. Other gases that can occur as a by-product of waste decay include carbon dioxide, nitrous oxide, methane, and sulfur dioxide. Industrial waste may produce gaseous by-products such as chlorine during decomposition.
Exposure to toxic gas can cause a range of health problems and can even be fatal. Small amounts of sewer gas in indoor air can cause irritation of the eyes, sore throat, cough, and pulmonary edema. Low appetite, headaches, fatigue, dizziness, memory problems, and irritability may occur in those exposed to low levels of these gases for a longer period. Strong concentrations of this gas can lead to unconsciousness and eventually prove fatal.
Sewer gas can generally be identified by its smell, which is said to be reminiscent of rotten eggs. Strong concentrations of these gases can, however, impair the sense of smell, making the stench of the gases impossible to detect. These gases are also generally extremely flammable.
Those who work in maintaining and cleaning sewers, septic tanks, or manure tanks may be most likely to be exposed to dangerous gas. This mixture of gases can leak into the indoor air of a home if the home's plumbing pipes, drains, and vents are poorly maintained.
Most homes have plumbing vents on the roof that allow gas to escape from the home's plumbing system. Keeping these vents clear can help keep sewer gas from leaking into the home. Properly maintaining and cleaning drains and pipes within the home can also stop the leakage of dangerous gases.
Homeowners who suspect a sewer gas leak are generally advised not to occupy their homes until the leak is resolved. Public health authorities and local fire departments may need to be notified of the problem. A professional plumber can usually be contracted to resolve the situation.