US Drug Test Centers Blog/News

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

Posted: Feb 28 2018

By: Jane Schwab

There’s a common myth that if you’re surrounded by enough marijuana smoke, the THC lingering in the air is enough to cause you to fail a drug test. It doesn’t help in clearing up this concern that cannabis is seeing a rise in potency, as certain strains of marijuana are being bred to hold more THC. What’s more, studies from the 1980s found that second-hand smoke could lead to a failed drug test.

Fortunately, these studies were inherently flawed, and exposure to second-hand smoke — or what many people refer to as a “contact high” — is not enough for you to test positive for marijuana.

Here’s what you need to know about second-hand smoke and drug test results.

Passive Exposure, and Why It’s Not Enough

When you take a urine test for marijuana, the test is looking for bodily byproducts of THC, which is the chemical that is largely responsible for producing the psychoactive effects associated with marijuana or THC related products. The misconception arises because people are under the impression that a contact high is enough for THC to show up in your urine.

Second-hand smoke is what some refer to as “passive exposure” — meaning you’re not actively inhaling any amount of THC directly from the source. This is important because the THC levels present in second-hand smoke are vastly different than the ones produced in active exposure. The amount of THC you might inhale through second-hand smoke is minimal — to be more precise, about 100 times less potent than THC levels from active exposure. Therefore, assuming you yourself haven’t been smoking, testing positive for THC just from second-hand smoke shouldn’t be a concern.

Are There Any Exceptions?

Is it possible to fail a drug test due to second-hand smoke exposure? Yes. Does that mean it’s likely or probable? Not at all. Research has found that even when you place smokers and non-smokers together in a car, even just the brief period before the drug test made the chance of a false positive THC test nearly impossible. Research further points out that you would need to be in a severely unventilated area to inhale so much second-hand smoke that you fail a drug test.

These conditions are extreme and not representative of the environment we typically find ourselves in. Furthermore, a drug test would have to be administered within hours of this type of exposure to have a significant influence on results.

The takeaway is simple: if you’re around people who are smoking and have concerns that THC might show up in your urine, rest assured that all you must do is refrain from smoking, and you’ll likely be just fine.

man with smoke

The Importance of a Comprehensive Workplace Drug Policy

In the event of a positive test, no matter the cause, it’s important to have a thoroughly documented drug-free workplace policy in place to establish how and when consequences are enforced. On the employer side, a comprehensive policy can provide protection if and when an employee is tested and/or reprimanded for a positive drug test result. On the employee side, a clear policy helps you understand what's expected of you and what the potential consequences are of breaking the rules. 

Especially in today's age of the widespread legalization of marijuana — not to mention our nation's opioid problem — having a policy is absolutely vital. US Drug Test Centers can help. We offer several drug and alcohol testing panels, we can customize a panel for you, and we even offer instant drug testing. With more than 20,000 locations across the United States, we're never far away. Call (866) 566-0261 or email info@usdrugtestcenters.com to get started. 


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