Attached garages are very convenient, but there is mounting evidence that they are responsible for negatively affecting indoor air quality. That’s because much of what we use our garages for (cars, mowers, paints, lubricants) contains or generates substances that are considered toxic. Once the toxic substances become airborne, they can easily migrate indoors.
It’s a bit ironic that we keep a floor mat by the door leading from the garage to the house so that shoe bottoms can be cleaned of largely nontoxic items like dirt, yet we often take no such preventative measures regarding the air.
Car exhaust, toxic chemicals and volatile organic compounds are present in almost all garages at least some of the time. And they can find their way into the house very easily through open doors, gaps around closed doors, ducts and other wall and ceiling penetrations.
There is scientific proof to back up this claim. A study involving 100 houses conducted by Health Canada found that those with attached garages had measurable quantities of benzene inside the house, while houses without attached garages had little if any benzene. Benzene is a gasoline-related pollutant. The study found similar results with other pollutants.
According to the U.S. Occupational Safety and Health Administration (OSHA), long-term exposure to benzene can affect bone marrow and blood production. Short-term exposure to high levels can cause drowsiness, dizziness, unconsciousness and death.
A survey of Minnesota houses during the winter of 1996-1997 found that 74 percent of homes with carbon monoxide (CO) detectors that went off were triggered by CO leaking in from the garage. Other studies from Iowa, Colorado and Alaska have found substantial evidence of garage-generated CO leaking into houses.
Nobody wants to breathe toxic pollutants, especially at home. Fortunately, there are a series of steps you can take to keep your indoor air quality something you need not worry about inhaling. Here are some tips:
- Keep the garage air clean. Avoid running the car, motorcycle, chain saw or lawn mower any longer than absolutely necessary while in the garage. Avoid placing mechanical systems such as water heaters and furnaces in the garage.
- Seal the gaps. Make sure the door leading from the garage into the house closes tightly and has proper weatherstripping applied. Seal all penetrations (ducts, wiring, etc.) leading into the house or the ceiling above the garage. Spray foam and caulk are good products for sealing these types of gaps.
- Finish the walls and ceilings. In new houses it is not uncommon for the garage to be left with open walls or with drywall attached but the joints not finished. Either of these conditions allow garage pollutants to easily find their way inside. Garage walls and ceilings that are completely covered with drywall, with joints properly sealed with tape and compound, and with the surface primed and painted are much less likely to leak. They are also much more attractive. (See How To Install Drywall Like a Pro.)
- Keep the door shut. Often you find yourself with full arms when entering the house from the garage. The result can be that the door remains open until you set the groceries down somewhere. Or maybe you or the kids simply forget to close the door, or fail to close it all the way. This can allow nasty fumes from the garage to enter the house quickly and easily. You can avoid this problem by installing a self-closing door.
- Keep the door open. Never start your car or any other internal combustion engine while the garage door is closed. And when you do start the engine after the door has been opened, move it outside as soon as possible and shut the door to prevent exhaust fumes from floating back into the garage. When you pull your car into the garage, shut it off as soon as possible and leave the door open for a few minutes to clear the air.
- Put a lid on it. Make sure all containers of potentially toxic items are sealed. Don’t let cans of paint thinner, solvents and other liquids sit uncovered.
- Vent it outdoors. If you spend a lot of time in the garage working with chemicals, paints, wood finishes, combustion engines and other such items, consider installing an exhaust fan that sends the smells and fumes to the outdoors. A decent bathroom or kitchen fan will be sufficient.
If you are planning to build a new house or garage, give some thought to making the garage fully detached from the house. In addition to largely eliminating garage pollutants from migrating inside the house, here are some other benefits of a detached garage.
Finally, make sure your home has at least one CO detector mounted probably. And, if you are curious about the CO levels in your garage, go ahead and mount one out there, at least temporarily, to see if it goes off on a regular basis. Though it might be irritating, it could be educational to learn that the air you are breathing in that space contains a toxic substance.
Photo courtesy flickr/Creative Commons