GAMAzine: Tight Homes Can Affect Combustion Appliances
In addition to consumer-driven energy improvements, federal and state energy codes have created tighter houses, resulting in very low air exchange rates, which requires supplemental mechanical ventilation systems, such as heat recovery ventilators. If adequate ventilation air is not provided, either naturally or mechanically, the home cannot "breathe" with the outside air. This situation is further exacerbated by consumers adding new exhaust fans (some of them continuously operating), or installing a new cooktop or range that utilizes a downdraft ventilation system.
Upsetting the delicate balance of a home's ventilation rate can result in a condition referred to as depressurization. This condition is capable of overcoming the natural draft established by combustion appliances, causing the flue gases to spill into living spaces instead of being safely vented to the outdoors.