Does your home have an attached, enclosed garage? You may want to reconsider parking your car inside. A study by Health Canada looked at the indoor air quality of 100 homes. Those with an attached garages had higher levels of benzene, and those that did not have attached garage had little to no readings. Why does this matter? Because benzene is a toxic chemical that's related to gasoline. But if you want to park your car indoors, do this: Leave the garage door open for a few minutes after you get home. This will help flush out the toxic chemicals to keep your indoor air clean.