Myth 13: Passive inhalation is a legitimate defense for a positive marijuana test.

Fact: The 15 nanograms per milliliter limit is so high that youd have to stay locked in a closet with Cheech and Chong while the smoked a dozen joints. Riding in a car with someone who is smoking grass wont expose you to enough to make you pop positive, Gustafson said, and the lab guys will testify to that. Can your lawyer get you off anyway? Depends. You've seen CSI.