Fuel burning appliances which do not draw combustion air from outside the home are subject to back drafting, which occurs when flue gases, including CO, are drawn back through the flue into the living space in the home. This occurs because of an air pressure drop in the home resulting from high wind conditions or in tight homes when local exhaust fans are used without adequate make-up air. Blocked or partially blocked flues may also cause back drafting. Flues should be inspected regularly. If you suspect back drafting contact your furnace service representative or your fuel supplier.
Power outages are a time of higher risk.
During power outages, people often resort to the use of kerosene space heaters, fireplaces, gas ranges, and even barbecues to heat homes. Do not use barbecues or gas ranges for a heat source. If unvented fuel burning space heaters are used for warmth, be sure that windows are opened slightly to provide fresh air into the living areas. Additionally, gas ranges should not be used without local exhaust, such as exhaust fans or vented hoods that are exhausted to the outside. Combustion Tobacco smoke, including second hand smoke, is a large source of CO in homes with smokers.