Medically Reviewed by
Jason Crawford

Article Last Updated on December 23, 2022

There are many reasons why some people avoid weed smoke apart from being nonsmokers – maybe they’re trying to cut down on their weed habits and are avoiding temptation. Maybe they have a sensitive throat, and smoke easily makes them cough. Or maybe they’re preparing for an upcoming drug testing and are avoiding weed in any form so as not to test positive.

Fortunately, the legal status of cannabis use has changed and weed enthusiasts can freely enjoy marijuana in various forms, including medical marijuana. However, there are still drug tests being performed in workplaces as many employers want to check for drug abuse. This may put stress on some cannabis users as well as non-users who are frequently around people who use marijuana.

Whether weed can get into your system by just being around it is frequently discussed, especially in the context of drug tests. If you’re trying to stay away from smoking weed for a while so you don’t get positive results on the drug test, but your friends are still puffing away on your get-togethers, you might want to know more.

In this article, we’ll discuss the effects of secondhand weed smoke and whether it can get you high, as well as whether it can be detected in your body.

What Are the Health Risks of Secondhand Smoke Exposure?

Tobacco smoke is known to carry a lot of health risks, so the debate about marijuana smoke (and its health effects) is not unexpected. Smoking marijuana involves combusting the plant material – a process that releases numerous toxins that are harmful to the lungs and overall health. Vaping is considered a healthier alternative as it doesn’t involve combustion, but it still needs to be more thoroughly examined.

Overall, smoke is the bad guy. Everyone knows how harmful smoke is for the lungs as it contains many byproducts that can cause health issues.

Can You Get High From a Secondhand Cannabis Smoke?

Feeling the psychoactive effects of marijuana from passive smoking, also known as “contact high,” is a valid concern that many people have. If you’re frequently in close proximity with a marijuana user who often smokes, you may wonder if you can actually get high by just being around them. Science has examined this phenomenon and the results are pretty interesting.

Johns Hopkins University School of Medicine conducted a clinical trial in 2015 whose objective was to examine the “physiological, subjective, and behavioral/cognitive effects of secondhand cannabis exposure, and the influence of room ventilation on these effects.” The participants were marijuana smokers and nonsmokers, and the study was done in two sessions. Each session produced different results that are key to understanding the effects of secondhand marijuana smoke.

During the first session, the participants were seated together in an unventilated room for an hour. During this time, the smokers were smoking marijuana, while the nonsmokers were passively inhaling the smoke. For the second session, the setting was exactly the same, except that it was done in a ventilated room.

Seems Like Ventilation Is the Key

The results from the first session indicated that the nonsmokers had detectable levels of THC in their blood and urine samples. Their heart rate was mildly increased and they reported feeling mild to moderate tiredness and sluggishness. Additionally, they showed mild impairment on cognitive and performance assessments that were done before and after the session for comparison.

On the other hand, the results from the second session, where there was ample ventilation, point to the opposite. Some participants had a detectable amount of THC in their blood immediately after exposure, but it was significantly lower compared to the first session, and it quickly became undetectable. None of the participants had detectable traces of cannabinoids in their urine, none reported feeling different afterward, and also their cognitive and performance assessments didn’t show any impairments.

So Then, No Contact High?

Since this study was done in controlled lab conditions, it could be said that it’s not 100% true to real-life situations, but it tells us a lot about how secondhand marijuana smoke behaves. Therefore, it’s not impossible to get a contact high. If you’re in a confined space with the windows closed, like a car or a smaller room, and you’re surrounded by at least two people who are smoking marijuana for over an hour, then it’s possible for weed to get in your system and to feel a mild buzz.

However, if you’re in an open space where people are smoking weed, or you happen to be sniffing weed from far away (or even when you’re just passing by), you’re hardly going to feel anything, let alone get high.

Will Secondhand Marijuana Smoke Show Up on a Drug Test?

Urine tests are the most frequently used tests in workplaces due to their accuracy and ease of use. They are designed to detect THC metabolites, which are byproducts that get released when the body starts to degrade THC.

From all the information above, we can conclude that it is indeed possible for secondhand weed smoke to be detected in the urine. However, in normal conditions, the THC metabolites present in urine simply won’t be high enough to cause a positive drug test result. The test would have to be able to detect even the smallest amount of THC, and standard drug tests aren’t that sensitive as they have a higher threshold.

Should I Stay Away From Secondhand Weed Smoke Before an Upcoming Drug Test?

If you’re concerned about your drug test, especially if you’re a regular marijuana smoker who’s abstaining due to the upcoming drug testing, then keeping yourself away from secondhand smoke is the safest option. Even though it probably wouldn’t make that much of a difference, it will help you be less anxious about it.

If you’re a non-user and need to get tested at work, then it’s highly unlikely that you’ll have detectable levels of THC in your urine if you’ve been exposed to secondhand smoke.

Bottom Line

Having concerns about secondhand weed smoke exposure is common, especially before an upcoming drug test. So far, science has shown that only in extreme conditions can weed smoke be detectable on a drug test and cause a contact high. However, in real-life conditions, this is highly unlikely. Room ventilation seems to have the biggest influence on whether weed smoke would affect you in any way. When there is ample ventilation, it should be undetectable.

Additional Resources

Ribeiro, L. I., & Ind, P. W. (2016). Effect of cannabis smoking on lung function and respiratory symptoms: a structured literature review. NPJ primary care respiratory medicine, 26, 16071. https://doi.org/10.1038/npjpcrm.2016.71

Tashkin D. P. (2013). Effects of marijuana smoking on the lung. Annals of the American Thoracic Society, 10(3), 239–247. https://doi.org/10.1513/AnnalsATS.201212-127FR

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.