As the temperature drops, we are more likely to fire up our gas furnaces and wood-burning stoves to get extra cozy this winter. However, when we use our furnaces and stoves, and spend more time indoors, we are at increased risk of exposure to carbon monoxide. Carbon monoxide is an odorless, invisible gas produced when gasoline, natural gas, propane, kerosene, and other fuels are not completely burned during use. According to the EPA, this gas is one of the leading causes of poisoning death, with more than 400 victims in the United States each year.