Can You Fail a Drug Test From Second-Hand Smoke?

Daniel Miller
Daniel Miller, Ph.D, Drug Testing Specialist

Last updated on Apr 9, 2024

The search for methods that work in passing scheduled urine drug tests is a real struggle among stoners. There’s a reason to worry, too, even if you’ve never puffed a joint in your life, but you are always amidst marijuana smokers whether in dorms, concerts, clubs, or your apartment.

The word on the internet is that inhaling secondhand smoke can get you high and even lead to a failed urine test.

So, how true is that? Is that a cause for alarm? To answer these questions, we need to understand whether exhaled cannabis smoke has THC or THC metabolites.

If so, we also need to determine whether it’s in levels that can get you stoned and later get excreted through urine.

Meet Ross Rebagliati

Ross Rebagliati is a Canadian pro snowboarder who was the first-ever to win a gold medal in men’s snowboarding.

We could also refer to Ross as the ‘father’ of the hypothesis that secondhand marijuana smoke can lead to a failed drug test.

This was his argument in 1998 when his win was automatically disqualified after THC was found in his blood system (this decision was later overturned, though).

Although most people didn’t buy his argument then, it brought about the need for deeper studies around this issue. And it’s not until recently that it was found out that Ross might have had a point all along.

You could get HIGH from second-hand smoke.

There are lots of studies that have been carried out around this topic, and they all claim that secondhand smoke can cause a contact high and can even lead to a failed drug test.

The most cited of these is a study conducted by Johns Hopkins Medicine and recorded in the Journal of Drugs and Alcohol Dependence.

In this study, researchers recruited seven smokers who said they had a joint at least twice per week and tested positive for cannabis but negative for other drugs.

12 others within the same age bracket said they had not stoned for the last six months and tested negative for cannabis and other drugs.

In the first session, one group consisting of 6 smokers and six nonsmokers was placed in a 10ft by 13ft acrylic-walled room side by side. The smokers were given ten high-potency cannabis cigarettes to smoke for one hour with the fans turned on.

In the second session, the other group consisting of 6 smokers and six nonsmokers was put in a similar room side by side where the smokers were asked to smoke ten joints for an hour but with the fans turned off. As you can imagine, the room in the second scenario was smoke-filled.

Blood, saliva, urine, and hair specimens were obtained from the 2 groups and tested for THC at regular intervals after the exposures.

There were detectable THC levels in the urine and blood samples from all the nonsmokers who were exposed to secondhand smoke in the unventilated room. THC in blood was observed immediately after the exposure and up to 3 hours later.

Between 2 and 22 hours after the end of the exposure, 4 of the 6 urine samples from the unventilated exposure tested positive for THC using a lower cutoff level of 20 ng/ml but negative for the 50 ng/ml that is used by most laboratories.

4 hours after the experiment, only 1 urine sample tested positive using the 50 ng/m cutoff level.

All the non-smokers exposed to secondhand smoke in the unventilated room reported that they felt a ‘pleasant’ feeling and felt ‘tired’ and less alert.

The researchers also found out that the subjects from the unventilated session responded faster when asked to perform a basic numbers drill. Still, they also made more mistakes than they made before the exposure.

Nonsmokers from the ventilated exposure passed the test using 50 ng/ml and 20 ng/ml cutoff levels and didn’t report any strange feeling besides being hungry.

Failing a urine test from secondary smoke? Not so easy!

Going by the results from the study above, it is evident that exhaled cannabis smoke does have some traces of THC.

This is proved by yet another study carried out in a similar design by the University of Calgary’s Cummings School of Medicine.

It showed that THC had reached detectable levels in the blood of non-smokers in 15 minutes of being exposed to cannabis smoke in a poorly ventilated room.

Besides, the cases of slight impairment observed with the non-smokers in the unventilated setup are clear indications that you can actually get HIGH from secondary smoke.

However, as Evan S. Herrmann, one of the researchers in the Johns Hopkins study, says, this study demonstrated the ‘worst scenario’- being in an unventilated room with 10 smokers doing it heavily for 1 hour. This is what the stoning community refers to as a ‘Hotbox.’

Herrmann continues to say that this is a situation that you’ll only find yourself in if you really want to. The scenario of the non-smokers in the ventilated room is a realistic simulation of most of the conditions that you are likely to find yourself in, let’s say in a concert or if you share a room with a heavy smoker.

Although exhaled cannabis smoke has traces of THC, the level is so low to cause a significant concentration that would lead to a failed drug test unless you are in a hotbox.

In the scenario above, the fact that the non-smokers passed the test with both the 20 ng/ml and 50 ng/ml cutoff levels indicates the low amounts of secondary THC concentration that make it to your blood system in a ventilated room.

This is to say that you shouldn’t worry so much if you recently got exposed to cannabis smoke in the days leading to a test.

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The information on this website about detox products and synthetic urines is for educational purposes only. We do not endorse or condone their illegal use. Always consider the laws in your area and the potential legal consequences. Consult with a healthcare professional before using any products. Your responsibility and well-being are paramount.