Carbon monoxide (CO) is an odorless, colorless, tasteless and nonirritating gas that is a natural by-product of combustion when fuel-burning appliances are operating. These appliances can include gas furnaces, gas water heaters, fireplaces, wood-burning stoves, gas ranges or ovens, gas dryers, kerosene heaters, charcoal/gas grills, lawn mowers, snow blowers, and chain saws. A crack in the flue system, blocked chimney, appliance malfunction or car left running in an attached garage are some of the ways CO can leak indoors, making residents sick. Exposure to lower levels of CO over several hours can be just as dangerous as exposure to higher levels for a few minutes. Symptoms of carbon monoxide poisoning can mimic the flu and include headache, fatigue, sleepiness, nausea, trouble breathing, diarrhea and dizziness. Those most at risk are children, the elderly, pregnant women and people with lung or heart disease. Early detection of carbon monoxide is possible with a UL listed carbon monoxide detector placed on every level of the home. If the detector goes off, call 9-1-1, leave the house, and wait for help in a well-ventilated area. For further information, view our Carbon Monoxide Safety brochure.