Can You Fail a Drug Test from Secondhand Smoke? Passive Smoking Myths Debunked

Can you get a secondhand high?

If you’ve ever been exposed to it, you may have wondered if you can get high from secondhand smoke. The answer is no, you probably don’t get high from someone else’s smoke.

The common phrase “contact high” implies that if you breathe in secondhand smoke from cannabis, you may feel a buzz (e.g., your thinking may become fuzzy or you may become sleepy). According to some studies, in circumstances when lots of cannabis smoke is blown straight into someone’s face, they may feel a secondhand high, and cannabis may be detected in a urine drug test. However, this occurrence isn’t normal.

Research studies show that when a cannabis smoker exhales, they breathe a very small amount of tetrahydrocannabinol (THC) back in the air. The amount of THC is so little that even if you’re in a room for an hour with people smoking about four joints (cannabis cigarettes), you may not get a secondhand high.

In order to get a secondhand high, you would need to confine yourself in a room with secondhand smoke from at least 16 joints.

One study found that people in an enclosed space with others smoking high-THC-content joints developed a mild contact high and experienced a mild impairment in their motor skills.

Can you fail a drug test from secondhand smoke?

You probably won’t fail a drug test from secondhand smoke. Since cannabis smokers exhale a very small quantity of THC, it would take a lot of exposure to fail a drug test from secondhand smoke.

Researchers have studied the effect of secondhand cannabis smoke on nonsmokers. During the study, the nonsmokers and smokers were placed together in a well-ventilated room for three hours. The researchers tested the nonsmokers’ urine and blood. Although the samples did contain THC, it wasn’t enough to fail a drug test.

Another study measured secondhand smoke exposure and varied the levels of cannabis potency and the ventilation levels of the room. Some nonsmokers who were exposed to high-THC secondhand smoke (11.3 percent) in a poorly ventilated room tested positive for the drug directly after the exposure.

The ventilation of a room may make a big difference. If you’re in an unventilated room and someone breathes secondhand cannabis smoke into your face, you may get high. If the room is well-ventilated, you may not get a buzz, but you could still fail a drug test from secondhand smoke. These are unlikely scenarios, though, and the effects may only be detectable in the hours immediately after exposure.

How long does THC stay in your system when taken directly?

THC is detectable in your system (in body fluids such as urine, saliva, and blood) for up to 30 days. It can stay in your hair for a few months. The amount of time that THC stays in your system depends on how much you took and how frequently. Generally, using it more frequently and in higher doses increases the amount of time it stays in your system.

Drug tests can detect cannabis in your urine according to the following timelines:

• Occasional users (three times a week) — detectable up to 3 days after use
• Moderate users (four times a week) — detectable up to 5–7 days after use
• Chronic users (daily) — detectable up to 10–15 days after use
• Chronic heavy users (multiple times a day) — detectable up to a month or more after use 

Drug tests can detect cannabis in your blood for one to two days. The metabolites of cannabis can stay in your blood for several days.

Drug tests can detect cannabis in your saliva according to the following timelines:

• Occasional users — detectable 1–3 days after use
• Chronic users — detectable 1–29 days after use

Tests of hair follicles can detect cannabis for up to three months. Cannabis can reach your hair follicles through tiny blood vessels. It can stay in your hair in trace amounts.

If you’re exposed to secondhand cannabis smoke, THC will be absorbed in your system. However, concentration is rather small. Drug tests can detect THC from secondhand smoke in blood samples taken a few hours after exposure, but it isn’t detectable after six hours.

In summary

Can you get high from secondhand smoke? Probably not. In order to get a secondhand high, you’d need to sit in a poorly ventilated room and breathe the secondhand smoke from at least 16 joints. Can you fail a drug test from secondhand smoke? In very rare cases and immediately after exposure, you could fail a drug test from secondhand cannabis smoke, but the likelihood is low.