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Updated on October 17, 2021

Can You Fail a Drug Test From Secondhand Smoke?

Can You Get ‘High’ From Secondhand Marijuana Smoke?

The simple answer is yes.

However, the ‘high’ you get from secondhand smoke is not the same as the one produced from physically ingesting marijuana.

Every time someone smokes a substance (e.g., tobacco or marijuana), the exhaled smoke contains traces of the active ingredients. 

In the case of marijuana, secondhand smoke contains residual THC, CBD, and other cannabinoids. 

If you are exposed to secondhand mariuana smoke, THC (marijuana’s active ingredient) may be found in your blood. But the amount of THC is much less than it would be if you smoked or ingested marijuana yourself. The levels also won’t trigger a failed drug test. 

Secondhand marijuana smoke contains residual amounts of THC. The lungs won’t absorb the THC—but you can still get high.

Hotboxing & Secondhand Marijuana ‘High’

Some marijuana users practice ‘hotboxing’ to enhance the effects. A hotbox is when people gather in a small room (sometimes a vehicle) with the doors and windows closed. This produces a stronger high than smoking alone because every inhalation contains marijuana smoke.

Although it’s possible to get high from secondhand cannabis smoke using a method like hotboxing, it doesn’t mean it’s easy. This is because the amount of smoke needed to achieve the desired—or undesired result—is significant.  

In most cases, simply being in a room with someone isn’t going to produce a significant contact high. If you aren’t a regular marijuana user, you’re likely to have a more intense experience from a contact high.

Secondhand marijuana smoke does not significantly raise THC levels in the body. But there are still concerns about the health and safety of passive smoking. 

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Can You Fail a Drug Test From Secondhand Smoke?

You’re unlikely to fail a drug test from secondhand smoke. However, it is possible depending on how much secondhand smoke you were exposed to and how ventilated the space was.

Drug tests have a cut-off level. This is the maximum concentration of THC the test allows in a sample. 

If your sample’s concentration is greater than the maximum concentration amount, you’ll fail the test. People exposed to secondhand smoke rarely reach this level, but it can happen.

According to a 2015 study from Johns Hopkins University, smokers and non-smokers were paired together in both ventilated and “hotbox” spaces.2 

The smokers were told to smoke 10 joints each for an hour. Following the hour, each group was drug tested using blood and urine samples.2

The non-smokers in the ventilated room felt no intoxicating effects and tested negative for THC. The non-smokers in the unventilated room felt intoxicated and tested positive for trace amounts of THC.2

But this trace amount of THC doesn’t remain in the system for very long. 

Unless you are spending time in a hotbox shortly before a drug test, you’ll likely pass a drug test even if you were recently exposed to secondhand smoke. 

What Current Research Says About Secondhand Smoke & Drug Tests

Several studies confirm the circumstances under which secondhand smoke produces trace amounts of THC in a drug test.

According to the first study, secondhand exposure to marijuana can show up on a drug test.1 

The goal of the study was to understand the health effects passive exposure had on non-smokers. The study reviewed 15 existing experimental studies to determine if THC could be detected in bodily fluids after exposure to secondhand smoke.1 

In addition to there being detectable levels of THC in the blood and urine of non-smokers, those exposed to secondhand smoke also reported feeling the psychoactive effects of the drug. 

However, the level of intoxication was weaker for non-smokers than for smokers.1

A second study showed that exposure to secondhand cannabis smoke leads to cannabinoid metabolites in bodily fluids. Study subjects also reported feeling the psychoactive effects of marijuana.2 

A third study conducted on lab rats showed that just a minute of exposure to marijuana substantially impairs endothelial function in the test subjects for at least 90 minutes. The endothelium is a thin membrane that lines the inside of the blood vessels and heart.

The study concluded that exposure could cause a similar adverse cardiovascular effect on people exposed to smoke (regardless of whether it came from tobacco or marijuana).3

Finally, a systematic study showed that extreme exposure to secondhand smoke can produce a positive urine test. These positive tests are rare and “occur only under environmental circumstances where exposure is obvious.”4

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How Long Does THC Stay in Your System?

The length of time THC remains in your system depends on how much you smoke and/or how much you were exposed to. 

THC’s metabolites remain in your body for much longer than the duration of effects. This means that, long after the high has worn off, a drug test could still detect recent marijuana use.  

In some cases, evidence of the drug can be detected for weeks or months after the last use. 

Determining how long the drug can trigger a positive drug test result is also based on the type of drug test being used. 

For example:

Blood Test

The body rapidly metabolizes THC, which means it will only remain detectable in the blood for a few hours or up to two days after a single use.

For heavy marijuana users, blood tests detect THC in the bloodstream for as long as one week.

Saliva Test 

THC appears in saliva about an hour after use and remains detectable for up to approximately one to two days after use. 

What you eat, how much you drink, brushing your teeth, or using mouthwash might speed the removal of THC from saliva. It’s for this reason that these types of tests are considered unreliable for marijuana testing.

Urine Test

This is the most common type of drug test for marijuana. THC is detectable for a longer period in urine (several weeks after use). The exact amount of time it’s detectable in urine depends on how often you use the drug. 

Additionally, frequency of use plays a role. Frequent/daily users can test positive for up to 65 days after the last use.

Hair Test

THC metabolites remain in the hair for longer than any other system in the body. 

The average length of time evidence remains present is about three months. However, people with longer hair test positive for THC longer than those with short hair.

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  1. Holitzki, Hannah, et al. “Health Effects of Exposure to Second- and Third-Hand Marijuana Smoke: A Systematic Review.” CMAJ Open, vol. 5, no. 4, 24 Nov. 2017, pp. E814–E822, 10.9778/cmajo.20170112.
  2. Secondhand Marijuana Smoke Can Cause Range of Detectable Effects, Study Finds.” The Hub, 15 May 2015.
  3. Wang, Xiaoyin, et al. “One Minute of Marijuana Secondhand Smoke Exposure Substantially Impairs Vascular Endothelial Function.” Journal of the American Heart Association, vol. 5, no. 8, 8 Aug. 2016, 10.1161/jaha.116.003858.
  4. Cone, Edward J., et al. “Non-Smoker Exposure to Secondhand Cannabis Smoke. I. Urine Screening and Confirmation Results.” Journal of Analytical Toxicology, vol. 39, no. 1, 17 Oct. 2014, pp. 1–12, 10.1093/jat/bku116.
  5. Secondhand Smoke and Cancer.” National Cancer Institute,, 2009. National Institute on Drug Abuse. “What Are the Effects of Secondhand Exposure to Marijuana Smoke?”, 2018.

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