Uploaded April 2019 | Updated September 2026, 1 week ago
Most people have at one time or another stepped into a home or building and were overwhelmed by an obnoxious odor, often smelling like rotten eggs. Ask an indoor environmental quality (IEQ) professional about that smell and many will say it is quite likely due to sewer gas, a common cause of indoor air quality (IAQ) and mystery odor complaints.
What causes sewer gas to stink so badly?
According to the Wisconsin Department of Health Services, sewer gas is a complex mixture of toxic and nontoxic gases that can be present at varying levels depending upon the source. It is formed during the decay of household and industrial waste. Highly toxic components of sewer gas include hydrogen sulfide and ammonia. Sewer gas also contains methane, carbon dioxide, sulfur dioxide and nitrous oxides. The agency reports that chlorine bleaches, industrial solvents and gasoline are also frequently present in municipal and privately owned sewage treatment systems.
What are some of the health effects of sewer gas exposure?
Sewer gas is a concern due to its unpleasant odor and potential health effects associated with exposure to toxic gases. As reported by the Wisconsin Department of Health Services, exposure to low levels of hydrogen sulfide can cause irritation of the eyes and respiratory tract. Other symptoms include nervousness, dizziness, nausea, headache and drowsiness. Indoor exposure to elevated concentrations of other sewer gases, such as methane and ammonia, can also lead to health concerns.
In extreme cases, not typically encountered in most homes or buildings, very high concentrations of sewer gas could lead to loss of consciousness and death or become a potential explosion and fire hazard.
How does sewer gas enter a home or building?
Sewer gas can enter a home or building through a dry, damaged or improperly designed drain; from a leaking or blocked plumbing roof vent; or (if the gases are in the soil adjacent to the building) through cracks in the foundation. To help prevent exposure to sewer gas, flush floor and sink drains and other plumbing fixtures with water to prevent the traps in the pipes from drying out. There are products available that are designed specifically to help prevent rarely used drains from drying out. Also occasionally check the roof plumbing vents for any signs of blockage (caused by debris such as leaves or bird nests) and make sure that these exhaust vents are not located too closely to air intakes or windows used for ventilation.
Indoor environmental quality and building science professionals can test for sewer gases and check to see if the building is under negative air pressure which could be contributing to the problem.
These are just a few things to know about sewer gas and how it can impact the indoor environment. To learn more about this or other building science, environmental, indoor air quality, occupational, health or safety issues, please visit the websites shown below.
Clark Seif Clark csceng.com
EMSL Analytical, Inc. emsl.com
LA Testing latesting.com
Zimmetry Environmental zimmetry.com
Sewer Gas Solutions sewergassolutions.com
Healthy Indoors Magazine healthyindoors.com
Most people have at one time or another stepped into a home or building and were overwhelmed by an obnoxious odor, often smelling like rotten eggs. Ask an indoor environmental quality (IEQ) professional about that smell and many will say it is quite likely due to sewer gas, a common cause of indoor air quality (IAQ) and mystery odor complaints.
What causes sewer gas to stink so badly?
According to the Wisconsin Department of Health Services, sewer gas is a complex mixture of toxic and nontoxic gases that can be present at varying levels depending upon the source. It is formed during the decay of household and industrial waste. Highly toxic components of sewer gas include hydrogen sulfide and ammonia. Sewer gas also contains methane, carbon dioxide, sulfur dioxide and nitrous oxides. The agency reports that chlorine bleaches, industrial solvents and gasoline are also frequently present in municipal and privately owned sewage treatment systems.
What are some of the health effects of sewer gas exposure?
Sewer gas is a concern due to its unpleasant odor and potential health effects associated with exposure to toxic gases. As reported by the Wisconsin Department of Health Services, exposure to low levels of hydrogen sulfide can cause irritation of the eyes and respiratory tract. Other symptoms include nervousness, dizziness, nausea, headache and drowsiness. Indoor exposure to elevated concentrations of other sewer gases, such as methane and ammonia, can also lead to health concerns.
In extreme cases, not typically encountered in most homes or buildings, very high concentrations of sewer gas could lead to loss of consciousness and death or become a potential explosion and fire hazard.
How does sewer gas enter a home or building?
Sewer gas can enter a home or building through a dry, damaged or improperly designed drain; from a leaking or blocked plumbing roof vent; or (if the gases are in the soil adjacent to the building) through cracks in the foundation. To help prevent exposure to sewer gas, flush floor and sink drains and other plumbing fixtures with water to prevent the traps in the pipes from drying out. There are products available that are designed specifically to help prevent rarely used drains from drying out. Also occasionally check the roof plumbing vents for any signs of blockage (caused by debris such as leaves or bird nests) and make sure that these exhaust vents are not located too closely to air intakes or windows used for ventilation.
Indoor environmental quality and building science professionals can test for sewer gases and check to see if the building is under negative air pressure which could be contributing to the problem.
These are just a few things to know about sewer gas and how it can impact the indoor environment. To learn more about this or other building science, environmental, indoor air quality, occupational, health or safety issues, please visit the websites shown below.
Clark Seif Clark csceng.com
EMSL Analytical, Inc. emsl.com
LA Testing latesting.com
Zimmetry Environmental zimmetry.com
Sewer Gas Solutions sewergassolutions.com
Healthy Indoors Magazine healthyindoors.com
