Normally, your home breathes in air from the outside to replace air being used by combustion appliances. If your home is too well-sealed, these appliances may become starved for the air that allows them to operate properly. When that happens, vent reversal may occur. In other words, if the burners become starved for oxygen, carbon monoxide can be introduced into the home. But even older, less insulated homes can be vulnerable to the threat of carbon monoxide poisoning, particularly if the appliances have been improperly installed or not maintained.
Prevention is the most important step.
Taking proper safety measures will reduce your risk of carbon monoxide poisoning. Because vehicles are a major cause of carbon monoxide poisoning, always back your car out of the garage to let it warm up. Never leave it running in the confined space of a garage, particularly if the garage is attached to the home. The same holds true for lawn mowers or snowmobiles. Never use ovens or grills for heating devices.