Second-hand marijuana smoke and drug tests

Originally Published: March 20, 1998 - Last Updated / Reviewed On: April 12, 2012
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Dear Reader,

At ease. Most likely if you didn't smoke anything, you don't have to worry about your drug test. Second-hand marijuana smoke — buzz producing, or not — can leave traces of the chemical tetrahydrocannabinol (THC) in your urine for a day or so after breathing the smoke. However, the amount is usually not enough to make you test positive. Most drug tests have intentionally high standards to avoid false positive results due to incidental ingestion of second-hand smoke.

Hair testing (which is rarely done because the results are not as reliable as results from urine tests) can give information about someone's drug use over a longer time period, say a month or so, rather than just a few days (for most drugs), or a few weeks (with heavy marijuana smoking, for example).

By the way, in order for you to test positive for THC, the marijuana smoke would have to be so thick that it would irritate the eyes of smokers and passive smoke breathers alike. Avoiding smoke-filled cars, unventilated rooms, and other enclosed smoky spaces can help ensure that you can hang out while your friends toke and still be clean for bugle call in the morning.