Carbon monoxide sources include: Heaters, fireplaces, furnaces, appliances, and cooking sources that use coal, wood, petroleum products, and other fuels. Petroleum products include, but are not limited to, kerosene, natural gas, and propane. Equipment powered by internal combustion engines, such as cars, portable generators, lawnmowers, and power washers, emit carbon monoxide. Attached garages with doors, ductwork, or ventilation shafts that are connected directly to a living space are also considered "carbon monoxide sources".