“I was just in the room where pot was being smoked”
One common myth relating to oral fluid drug testing is that exposure to second hand marijuana smoke can cause a positive test result for THC. Many people believe that the recent rise in cannabis potency makes it more likely for false positives to occur. That is not the case.
Second hand smoke, or “passive exposure” to marijuana produces THC levels that are much different than those produced under active exposure. When a smoker exhales, very low levels of THC are released back into the air. This makes it extremely unlikely under normal circumstances for a non-smoker to inhale enough THC for an oral fluid test to turn positive.
In extreme cases, positive oral fluid test results from passive exposure are possible, but still unlikely. One study concluded that with an extreme lack of ventilation it is possible to test positive for THC from exposure to second hand smoke immediately after exposure and “only under environmental circumstances where exposure is obvious.” A second study placed both smokers and non-smokers together in a smaller environment: a vehicle. The results showed that when collected properly with a waiting period before collection, the risk of a false positive THC test was “virtually eliminated”.
THC levels caused by passive exposure are about 100 times less than levels caused by active exposure to marijuana. When administered properly, oral fluid tests leave no possibility for false positives due to passive exposure to THC.