Healthy indoor air quality
Carbon Monoxide Poisoning and Prevention: How to Protect Indoor Air Quality in Homes from CO Contamination
...Heating systems: Gas or oil furnaces, boilers, and wood-burning stoves are the most common interior sources, especially if heat exchangers are cracked or flues are blocked.
Water heaters: Natural gas or propane-fired water heaters can backdraft CO into the living space if venting systems are improperly sized or obstruc...
