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Fact Sheet

April 2010

EPA Sampling Completed in Sedgwick and Surrounding Counties, Sedgwick County Carbon Dioxide Site, Sedgwick County, Kansas


Last November, EPA Region 7 collected groundwater and soil vapor samples at 18 properties located in Sedgwick and surrounding counties. See sampling map (1 pg, 323K, About PDF) EPA collected the samples from residences where oxygen depletion had occurred in basements during major rainfall events in the area. The samples were analyzed to determine if any hazardous substance was present at a level of concern. EPA did not detect any hazardous substance at a level above health-based standards.

At three properties, EPA did detect methane at elevated concentrations. However, the levels of methane detected fell below the Lower Explosive Limit (LEL). There is no groundwater or other obvious chemical source for the methane detected in soil gas. Methane also occurs naturally and the detection may be the result of natural biological activities.  Follow up screening by Kansas Gas Service at those residences did not detect any elevated methane readings. EPA is mailing sample result letters to all residents whose properties were included in this sampling effort.


During the second week of September 2008, the greater Wichita metropolitan area experienced record rainfall and flooding. Some residents living in the area reported pilot light outages which occurred during the heavy rains. Local responders conducted air monitoring in the residential areas which reported the pilot light outages. Underground gases such as carbon dioxide and methane may have seeped into the basements during the heavy rainfall. These gases can reduce oxygen levels and may have caused the pilot lights to extinguish.

When carbon dioxide and methane concentrations rise too high within buildings, oxygen levels can fall dangerously low. This presents a health danger to the residents living in these homes. EPA Region 7 personnel conducted the recent sampling event to determine whether chemical contamination was the cause of the gas intrusion event.

Last October, the city of Wichita requested the assistance of an EPA research lab located in Ada, Oklahoma, to evaluate the oxygen depletion event which had affected some area residences during heavy rain. The EPA lab agreed to work with the city on a long-term study in an effort to identify the potential source of the gas intrusion that occurred last September.


Carbon dioxide is a nonflammable, colorless and odorless gas. It is removed from the body via the lungs in the exhaled air. Carbon dioxide is also produced when fossil fuels are burned. Surface soils can sometimes contain high concentrations of this gas from decaying vegetation or chemical changes in the bedrock. Because carbon dioxide is colorless and odorless, families living in homes affected by high concentrations typically aren't aware of the problem immediately. An area is considered oxygen deficient when the oxygen content goes below 19.5 percent. This means that the carbon dioxide concentration has exceeded the amount of normal air. Carbon dioxide can be dangerous in concentrations higher than 0.035 percent of normal air.


The amount of carbon dioxide in a building is usually related to how much fresh air is being brought into the building. In general, the higher the carbon dioxide level in a building, the lower the amount of fresh air exchange. Examining carbon dioxide levels in indoor air can reveal if heating, ventilation and air conditioning systems are operating within guidelines.

During periods of extremely heavy rainfall and flooding, the surface of the ground can become sealed off with water. This creates a blanket on top of the soil and does not allow soil vapors to escape through the soil. Soil gases that would normally seep into the air outside can instead be forced into basements through cracks in walls, floors or foundations, or service lines. Under these conditions, the level of oxygen can be reduced by the rising levels of soil gases.   


Methane is an odorless and colorless gas emitted from a variety of both human-related and natural sources. Human-related sources of methane include fossil fuel production, livestock and manure management, and landfills. Natural sources of methane include wetlands, gas hydrates, termites, non-wetland soils and other sources such as wildfires.


Methane is not toxic; however, when methane is present in the air at higher concentrations, it can displace oxygen and lead to oxygen deprivation. During periods of extremely heavy rainfall and flooding, methane may seep into basements and lower oxygen levels. If methane is present in sufficient concentration, a hazardous explosive atmosphere may also be created in the home.


When carbon dioxide and/or methane concentrations rise too high within buildings, oxygen levels can fall dangerously low. Exposure to high levels of carbon dioxide and/or methane can produce a variety of symptoms associated with oxygen deficiency. These symptoms may include headaches, dizziness, restlessness, a tingling or pins and needles feeling, difficulty breathing, sweating, tiredness, increased heart rate, and elevated blood pressure.


Do not sleep in basements that are experiencing even mild flooding. During flooding conditions, open windows or doors to allow circulation of fresh outdoor air into the basement. Use fans to direct outside air into the home.

Residents can fill cracks, joints, and gaps in walls, floors, and around service lines with an impermeable seal such as polyurethane caulk or hydraulic cement. This can help keep soil gases out of the basement.

Residents may also purchase an oxygen monitor to keep tabs on oxygen levels in the basement, especially during heavy rain events and flooding.
It is possible that installation of a radon reduction system could remove gases other than radon such as methane and carbon dioxide from residential basements. A radon reduction system draws outside fresh air and forces it under the basement slab. This increases the air pressure around a building foundation and drives the soil gases away from the building. This method is still being evaluated to determine its effectiveness in addressing methane and carbon dioxide.


If you would like more information on decreased oxygen levels in residences or other indoor environmental quality subjects, you can call the City of Wichita Office of Environmental Health at 316-268-8351.

If you have questions about EPA's ongoing sampling activities for the Sedgwick County Carbon Dioxide Site, you may contact

Dianna Whitaker
Community Involvement Coordinator
EPA Region 7
901 North 5th Street
Kansas City, KS 66101
913-551-7598, Toll-free 1-800-223-0425
E-mail: whitaker.dianna@epa.gov

Katy Miley
On-Scene Coordinator
EPA Region 7
901 North 5th Street
Kansas City, KS 66101
913-551-7916, Toll-free 1-800-223-0425
E-mail: miley.katy@epa.gov

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