Home and Garden

Known carbon monoxide (CO) risks include by-product emissions from a gas furnace or stove located inside your home. But dangers may be lurking in your attached garage, too.

Often, CO released from a running vehicle enters the home when someone simply opens the door. CO poses significant risks to the health of home occupants, causing problems ranging from headaches to flu symptoms, even death. Other times, the season and the seal of the shared wall create conditions that make CO seepage into the home more likely.

The proof

A study by the Canada Mortgage Housing Corporation shows that homes with attached garages have much higher CO concentrations than homes without, turning a convenient, must-have garage into a deadly weapon.

The unavoidable reality of CO emissions from a car are not the only factor that increase concentrations of it in a home. Weather conditions also contribute, and two factors make it possible:

• air movement. The wall of a garage (and perhaps the ceiling if the home is positioned above it) can weaken over time, developing tiny cracks and crevices that allow air and any CO present to move into the home. Further tests conducted by the CMHC revealed that significant leaks occur in the shared house-to-garage wall and is no less prone to leakage than rest of the home's structure.

• pressurization. Colder weather scenarios make the possibility of CO movement even more likely. As the temperature drops and homeowners run their vented heating systems, the home becomes depressurized. Even in mild climates and temperatures, running exhaust fans can cause the home's pressure to drop, too. Once the home is depressurized or it holds a lower pressure than the outdoors, the force of the pressure pulls outside air (and higher-pressured air that exists in a garage) into the home, bringing any CO that exists in the garage air along with it.