Can Secondhand Weed Smoke Cause You to Fail a Drug Test?

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You’ve been aware of an upcoming drug test for a while so when you’re in a smoke circle with friends and a joint’s been passed along to you, you’ve been good about not taking a hit. Good for you.

But will that secondhand smoke exposure cause you to fail the drug test?

What is Secondhand Smoke?

Secondhand smoke is the inhalation of smoke–and for the purposes of this discussion, marijuana smoke–by persons not smoking themselves. Typically, they are inhaling the exhaled smoke from smokers in close proximity.

Weed smoke contains more than 100 different types of chemicals most of which are toxic. It also contains delta-9-tetrahydrocannabinol best known as THC, the cannabinoid in weed that brings about the “high” in users.

Effects of Exposure to Secondhand Smoke

The effects of exposure vary largely depending on the potency of the weed, the amount of ventilation and the length of time one has been exposed to it. In some cases, a person exposed to marijuana smoke in an enclosed vehicle or other tight, poorly ventilated area may experience a contact high and become mildly impaired by said exposure.

A study of nonsmokers exposed to secondhand marijuana smoke for three hours found that THC showed up in small amounts in their blood tests even though their exposure had been in a well-ventilated area. However, the amount of THC did not meet the threshold to fail a drug test.

Cropped view of mature woman holding joint with weed and lighter

However, another study on nonsmokers exposed to potent marijuana having 11.3 percent THC for an hour in an unventilated space netted less encouraging results. When urine samples of the study subjects were tested immediately following the exposure, their test results came back positive for the marijuana metabolite 9-carboxy-THC.

Additionally, a follow-up study exposing nonsmokers to high-THC smoke found the test subjects experienced mild motor skill impairment.

Studies have also found that marijuana smoke can be absorbed through both the skin and hair.

Tests found that when it comes to hair follicle testing, darker-haired individuals are at a disadvantage to their blonder friends as their hair holds in more THC. Blondes, brunettes, and redheads, however, are at an equal advantage when it comes to topical creams applied to the skin.

Skin will absorb cannabinoids, but they don’t get into the bloodstream. Limited research has been done on the health hazards of being exposed to secondhand cannabis smoke.

A 2014 test on rodents found it caused reduced blood vessel function. And another test in 2016 on lab rats found signs of short-term lung impairment. Those poor rats!

But how secondhand marijuana smoke impacts human health is still yet to be determined. Because smoke of any kind is unhealthy for the lungs, the general belief is that those with lung and respiratory ailments, children, and other vulnerable populations should avoid exposing themselves to marijuana smoke.

Treatment For Secondhand Smoke

There is no treatment for secondhand smoke, but you can take preventive measures by limiting your exposure to it:

  1. Avoid confined areas where others are smoking or where there is poor ventilation.
  2. That COVID-19 mask with nose clips you’ve been wearing for months? Don’t be afraid to wear it when you’re at a party or other events where you’re likely to have a lot of exposure to marijuana smoke.
  3. Practice a healthy regimen by eating well, exercising frequently, and drinking plenty of water daily to keep you hydrated.
  4. Take zinc tablets as they could be effective in reducing the detection of THC metabolites for 12 to 18 hours.

Military Drug Test For Secondhand Smoke

The likelihood of failing a military drug test due to exposure to secondhand marijuana smoke is low, as in most cases the THC metabolites the military tests for would be too low to be traced.

However, many strains of marijuana in recent years have been developed to produce a higher THC content in the dry weed smoked. Therefore, if you’re planning on joining the military and have a drug test coming up, the best way to pass it is to refrain from smoking and avoid hanging out with your weed-smoking friends for a day or two before.

Don’t worry! They’ll understand.

By the way, don’t think that temporarily switching to edibles is a good solution. While there are many uses for your decarbed weed, the potent THC in your favorite brownie or cookie recipe will end up in your bloodstream.

Drug testing kits are also available for purchase online. If you test yourself and fail, they provide measures to follow to help you ensure your official test will have a positive – and by that, we mean “negative” – result.

Secondhand Smoke Laws In Texas

Several municipal ordinances prohibit the smoking of tobacco products in public places.

In addition, the Texas Public Housing Authority bans lit tobacco products inside the units and within 25 feet of any HUD housing. This includes cigarettes, cigars, pipes, and hookahs.

However, no such laws against marijuana smoking have been implemented for multi-unit residential settings in Texas.

Close up of dried marijuana leaves and joint

Whether tenants smoke tobacco or weed, the secondhand smoke from their units can spread throughout the buildings into other people’s living spaces. And multi-unit property owners have the legal right to prohibit smoking of any kind on their properties.

For those who have prescriptions for medical marijuana, the question often arises if they have the right to a “reasonable accommodation” under the federal Fair Housing Act.

This is a challenging situation for any state government that permits the use of medical marijuana. Because the U. S. Fair Housing Act states emphatically that a handicap “does not include current, illegal use of or addiction to a controlled substance,” no accommodation is required by multi-unit property owners for tenants who smoke medical marijuana.

Under federal law, marijuana continues to be categorized as a Schedule 1 drug, thereby identifying it as a drug with a high potential for abuse and of no medical use.


How Long Can Secondhand Smoke Stay In Your System?

How long the ingredients you’ve been exposed to in secondhand smoke will stay in your system can vary depending on the potency of the weed you’ve been exposed to, the length of time you’ve been exposed, and the ventilation in the area it was being smoked.

If you’ve been exposed to secondhand marijuana smoke, the THC metabolites in a urine sample will be present on average from two to five hours after the exposure. For blood tests, THC will be present for one to two days afterward.

A saliva test will detect THC anywhere from one to twelve hours after exposure.

How To Pass A Secondhand Smoke Drug Test?

Again, the best way to pass a drug test is to avoid being in the presence of anyone smoking weed for at least a couple of days before your test. If you are exposed, drink plenty of water and amp up your exercise routine to increase your metabolism rate.

Take a zinc tablet, too, for good measure as that can help suppress THC metabolites from showing up in your test. They are available at most local pharmacies.

Handsome man smoking weed

If you don’t have tablets, however, fill up on zinc-rich foods like bananas or chocolate or better yet, chocolate-covered bananas!

Are There Any Exceptions?

If your secondhand smoke exposure has been minimal, what little THC metabolites are in your system will be unlikely to reach the threshold that will cause you to fail your test. An exception might be if the THC in the weed you were exposed to was extremely potent.

If you’re worried about passing your test and you have time, it might be helpful to purchase a drug testing kit and test yourself at home. More likely than not, the results will put your mind at ease.


If you smoke weed and have an upcoming drug test for employment, entering the military, or any other reason, and you’ve quit for the time being, then good for you! But because secondhand smoke from other users around you can potentially give you a positive test result, you should also try to limit your exposure to it.

Healthy eating, drinking plenty of water, and adding more exercise to your daily regimen can help, as can taking a zinc tablet before your test.

However, studies have found that concentrations of THC in blood and urine don’t stay in the system all that long for those simply exposed to secondhand smoke. For the most part, steering clear of your weed-smoking friends for a couple of days should leave you also in the clear.