Will Secondhand Cannabis Smoke Show on a Drug Test?

Will Secondhand Cannabis Smoke Show on a Drug Test?

Most states−even those that have decriminalized or legalized cannabis−require drug tests in certain situations. Jobs for the Federal government or contractors to the Federal government override state regulations. Jobs where safety risks are high, such as operating heavy machinery or driving vehicles, will require drug tests for employment and, perhaps, periodically after that.

Drug testing has become more sophisticated, so even if you do not use cannabis, you need to know if secondhand cannabis smoke show in your drug test results?

Who is testing?

Thanks to the legalization of marijuana, drug use is at an all-time high. However, in most states, fewer than 2% of jobs require pre-employment testing, and fewer yet disclose that they may require testing later.

The following areas of employment are more likely to insist on pre-employment screening:

  • Aerospace

  • Health & Care Hospitals

  • Automotive

  • Information Technology

  • Construction

  • Logistics & Transportation

  • Defense

  • Manufacturing

  • Education & School Employment

  • Private Security

  • Government


 These positions involve handling heavy or sensitive machinery, working responsibly with people, and performing sensitive work. The jobs mandate clear focus, craft skills, and public compliance.

In addition, athletes competing in collegiate or professional sports will undergo periodic testing to ensure good health and competitive fairness.

How do they test these days?

Organizations administer a range of tests, some light and some in-depth. They are looking for the appearance of:

  • amphetamines

  • methadone

  • barbiturates

  • methamphetamines

  • benzodiazepines

  • opioids

  • cocaine

  • PCP

  • marijuana


The usual urine test requires you to pee in a cup which a lab assistant, nurse, or tech will then label and process. Most urine tests today produce positive or negative results immediately. They are testing for a cutoff point rather than the percentage presence of each drug.

On the other hand, a toxicology test uses urine, blood, saliva, or hair for a more thorough reading of each drug and its percentage content. In addition to the previously listed drugs, toxicology forensics may test for:

  • alcohol

  • oxycodone

  • codeine

  • THC (tetrahydrocannabinol)

  • heroin


A 10-panel drug screen is the most thorough and will reveal the presence of:

  • amphetamines: speed, crank, meth, Adderall, Ritalin, and more

  • barbiturates: amobarbital, pentobarbital, phenobarbital, and Tuinal

  • benzodiazepines: Ativan, Librium, Xanax, and Valium

  • cannabis: weed, hash, hash oil, and synthetic cannabis

  • cocaine: coke, crack cocaine, and rocks

  • methaqualone: Quaaludes

  • methadone: dollies, amidine, and red rock

  • opioids: heroin, opium, codeine, or morphine

  • phencyclidine: PCP and Angel Dust

  • propoxyphene: Darvon and PP-Cap

Organizations choose their testing protocol based on the sensitivity of the job accountabilities and the cost of the exam.

Will secondhand cannabis show up in the test results?

The effects of secondhand cannabis smoke may or may not show up in your drug test. If you have been occasionally or casually affected by cannabis smoke, cannabis properties will not likely show up in a urine test.

If you have experienced extreme exposure, secondhand cannabis smoke may be in your system and produce an undesired test result. For instance, if your roommate uses cannabis heavily and frequently, that smoke surrounds you and saturates everything around you. Even when the roommate is out of the room, you breathe its air. It can, therefore, enter your bloodstream enough to test positive for cannabis. Research studies suggest the average non-smoker would not tolerate such extreme exposure to smoke.

At Johns Hopkins University (2015), researchers paired non-smokers with marijuana smokers in a sealed room. They used different cannabis strains with varying levels of THC. In one session, they used a room without ventilation.

The non-smoking participants were urine tested almost 15 times in 34 hours. Only one of the participants tested above the preferred THC level. After 24 hours, no one tested positive for THC despite exposure to dense smoking environments.

A later Canadian study (2017) found, “Tetrahydrocannabinol metabolites are retained in the body upward of 4 hours, and people report the experience of psychoactive effects after exposure to secondhand smoke." However, testing does not detect the influences, nor do the effects test above acceptable levels.

What to do if you are worried?

If you do not use cannabis but have exposure to secondhand cannabis smoke, research indicates you need not worry about a drug test. Still, people do worry.

There are a few things you can do to reduce the anxiety:

  • Avoid situations where there is heavy exposure to cannabis smoke. If you join three or four frat brothers smoking in one room, you may walk away with a touch of a secondhand high. To be safe, you should avoid smoking circles in rooms with poor ventilation.

  • Hydrate heavily. You can wash any influences from your system with heavy water consumption. Drink eight large glasses of water before the exposure and for at least 24 hours after.

  • Take Zinc. Zinc supplements available at any pharmacy or health food store will reduce the presence of THC. Take Zinc as indicated on the label over 24 hours following the exposure.

What is your takeaway!

Casual or occasional exposure to secondhand cannabis smoke will not affect your drug test results. Heavy exposure to intensive cannabis smoke may not be healthy, but it is not likely to hurt your test results after 24 hours. This news applies to urine, blood, hair, and saliva tests.

However, frequent exposure to heavy secondhand cannabis smoke presents much the same risk as exposure to secondhand tobacco smoke. At the very least, you would benefit from a well-ventilated location.