Gas kitchen ranges releasing unvented combustion products into the kitchen are common in many homes. Studies show carbon monoxide concentrations in the kitchen are elevated when the stove is used without using the range hood.
What pollutants are released from a kitchen range? The main pollutants are carbon monoxide, carbon dioxide, nitrogen dioxide, and water vapor.
How serious is carbon monoxide from kitchen ranges? Carbon monoxide is a deadly toxin. In one study, 51 percent of kitchen ranges tested raised CO concentrations in the room above the EPA standard of 9 parts per million. Five percent had carbon monoxide levels above 200 parts per million.
How serious are the other pollutants? Nitrogen dioxide is a respiratory irritant produced when the nitrogen in the air combines with oxygen in the burner. The high number of gas ranges, the tightening of homes, the use of gas ranges to heat the home, and the increased incidence of asthma in the U.S. suggests a link between unvented gas heaters and health problems.
What about carbon dioxide and water vapor? Carbon dioxide is a non-toxic gas produced during complete combustion. At higher concentrations CO2 can cause drowsiness, headache, and lead to a “stuffy” feeling in a home. Excess water vapor can lead to problems with mold, wood rot, and peeling paint.
How much carbon monoxide is produced by a kitchen range? Carbon monoxide from kitchen ranges is a common reason for elevated concentrations of CO in homes. Kitchen ranges are required to produce no more than 800 parts per million (ppm) carbon monoxide in an air-free sample of the flue gases. Continued operation of a kitchen range producing 800 ppm in a tight house without extra ventilation will cause carbon monoxide levels to rise quickly to unacceptable levels. Field technicians report most kitchen ranges can be tuned to produce less than 50 ppm.
How can the adverse health effects from using a gas range be reduced?
- Have the furnace tuned for combustion safety by a qualified specialist.
- Follow operating instructions carefully:
- Do not block air vent holes.
- Do not cover the vent holes on the bottom of the oven with foil.
- Keep the unit clean.
- Do not operate with the oven door open.
- NEVER USE A KITCHEN RANGE TO HEAT THE HOME!
- Always use the kitchen range hood fan, vented to the outside, when operating the kitchen range.
- Have the range serviced when:
- Burner flames are not blue.
- The burners do not light properly.
- The burners or pilot produce soot.
- Carbon monoxide concentrations in the house increase during operation of the range.
- Evacuate the house, and call for assistance from outside the house if there is a smell of natural gas or LPG.
- Install a fire extinguisher, smoke detector, and carbon monoxide detector in the home.
How important is installation and use of an exhaust hood vented to the outdoors? Very. Even when the kitchen range is properly tuned, there will be some carbon monoxide produced along with carbon dioxide, nitrogen dioxide, and water vapor. Kitchen range manufacturers recommend installation of a range hood to exhaust the combustion products along with cooking odors, grease, and moisture produced during cooking. Failure to use the range hood exhaust fans results in indoor air pollution.
What should be considered when purchasing an exhaust hood? It must seal tightly and vent to the outdoors, operate quietly, and have sufficient capacity to remove cooking fumes. A caution: exhaust fans depressurize the house and may cause downdrafting of vented furnaces, water heaters, boilers, fireplaces, and vented room heaters. Adequate make-up air into the house must be provided for the kitchen exhaust hood. Have a qualified heating contractor install the exhaust hood and run a “worst case” downdrafting test to ensure that all the systems work correctly.
Why can’t the oven door be opened to heat the kitchen?
- The broiler and oven burners are designed to burn with the door closed.
- Opening the oven door disrupts the air flow pattern, and high concentrations of carbon monoxide may be produced.
- The oven burner is not designed to operate continuously, and can overheat.
- Kitchen ranges are designed for intermittent operation. Range standards allow concentrations of carbon monoxide that, under continuous operation, could create serious health problems. The longer the range operates, the more carbon monoxide produced.
- When the oven door is open, heat from the oven flows out the front, and can melt the control knobs or damage the controls.
I have an older kitchen range that sets off my carbon monoxide detector. Will buying a new range correct the problem? Since 1926 kitchen ranges have been allowed to emit up to 800 ppm of CO. A new range may emit as much or more than the old range. Have the old range inspected and tuned by a qualified contractor, one with instruments which measure for carbon monoxide in the flue gases. If you replace the range, have the new range adjusted for low carbon monoxide emissions after installation in your home!
How are ranges modified to burn natural gas or LP? By changing the gas regulator and orifices. Natural gas and LP have drastically different burning characteristics. If the changes are not correct, extremely high levels of carbon monoxide will be produced along with an increased risk of fire or explosion. Conversion should be made ONLY by a qualified contractor, with proper equipment, training, and parts. For a safe conversion, the contractor must measure for carbon monoxide and tune the range for minimum carbon monoxide production after conversion.
What about electric ranges? The electric elements in electric ranges do not produce combustion pollutants. Burning food produces smoke and carbon monoxide, and can cause smoke detectors and carbon monoxide detectors to alarm. So can self cleaning ovens during the clean cycle. Carbon monoxide is toxic, so if CO reaches concentrations high enough to set off an alarm, the alarm should be taken seriously. Open windows and leave the house until concentrations drop. If anyone experiences health problems, medical attention should be sought.
T.H. Greiner, Ph.D., P.E.
Extension Agricultural Engineer
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