Wood, coal, and charcoal fires always produce carbon monoxide, as do gasoline engines. Incorrectly installed venting systems and chimneys, chimneys plugged by birds nests or tree leaves, deteriorating chimneys which collapse, chimneys which are too short to vent correctly, appliances with no venting system, and house air flow patterns can all cause vent failure. Downdrafting results when air flow reverses in a vent or chimney pulling air back into the house instead of being expelled. Anything that moves air out of a house and depressurizes the house can downdraft a chimney. This includes exhaust fans, any vented heating appliance, fireplaces, and holes in the ceiling.
Tight homes can also downdraft when insufficient air is available for complete combustion.
First, the appliance must be serviced to eliminate the production of carbon monoxide. Second, the vent system must be inspected, repaired, or replaced as necessary. Carbon monoxide symptoms are similar to the flu and include headaches, fatigue, nausea, dizziness, confusion, and irritability. Continued exposure can lead to vomiting, loss of consciousness, brain damage, heart irregularity, breathing difficulties, muscle weakness, abortions and even death. Because the symptoms mimic so many illnesses, it is often misdiagnosed.