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Sewer Gas

Health & Human Service  /  Public Health  /  Environmental Health  /  Air Quality  /  Sewer Gas

Sewer Gas

Sewer gas is a complex mix of toxic and nontoxic gases that forms when household and industrial waste decay. The concentration of sewer gas typically varies depending on the source. Highly toxic components of sewer gas include hydrogen sulfide and ammonia.

Sewer gas also contains

  • Carbon dioxide.
  • Methane.
  • Nitrous oxides.
  • Sulfur dioxide.

Municipal and privately owned treatment systems can also contain:

  • Chlorine bleaches.
  • Gasoline.
  •  Industrial solvents.

What should I do if I suspect a problem?

First, try to follow the odor. Locate the point of entry, if possible, such as a basement floor drain. Then, check for a blocked rooftop plumbing gas vent. By adding water to the floor drain or removing debris from a vent, you may be able to prevent sewer gas from entering your home.

If the leak is behind the wall, you may need to hire a plumber to find the source and fix it. Some local public health departments offer home inspections.

Certain symptoms suggest exposure to gases like methane or carbon monoxide, which are odorless, or hydrogen sulfide, which smells like rotten eggs.

sewer smell flyer

These symptoms include:

  • Headaches
  • Dizziness
  • Drowsiness
  • Nausea
  • Nervousness

Hydrogen sulfide poisoning: Hydrogen sulfide smells like rotten eggs, even in low concentrations. Exposure to low levels of hydrogen sulfide can cause eye and respiratory irritation.

Suffocation: High concentrations of methane in enclosed areas decrease the amount of oxygen in the air and can cause suffocation. Very low oxygen concentration levels (less than 12%) can cause unconsciousness and death very quickly and without warning. The most concentrated levels of sewer gas collect where it’s entering the home, which is often in basements.

Explosion and fire: Methane and hydrogen sulfide gases are both flammable and highly explosive.

If you experience these symptoms and suspect a sewer gas leak in your home, see a doctor.

If you believe there are high concentrations of sewer gas in an enclosed space, evacuate the building and call the fire department for help. Also, avoid creating an ignition source, such as a spark from an electrical appliance, match, or cigarette lighter.

For more information on sewer gas, please click one of the links below:

WI DHS Sewer Gas

Hydrogen Sulfide