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USA Mobile Drug Testing of Central Long Island 516-802-3546 Legal NYS DNA Paternity Testing

Can Secondhand Smoke Cause a Positive Drug Test for Marijuana?

We get asked this question a lot at USA Mobile Drug Testing, so I did some researching for facts.If you are even slightly concerned about receiving a positive drug test, call our offices at 516-802-3546 or email and we can arrange for you to pre-test. We have mobile collectors to come to you or can arrange use of an affiliated walk in collection site.  Now the answer is: In rare occurrences, secondhand marijuana smoke can cause you to fail your drug test on

It is possible that secondhand marijuana smoke will raise someone to the 50 ng/mL level. However, extreme secondhand exposure is required. For instance, being in a closed car full of pot smokers for several hours might cause someone to test positive in a drug test the very next day. Non-smokers are safe in a ventilated area such as an average living room or garage where party-goers are smoking pot.

Another site said:

“It [second hand marijuana smoke] would not register on our instant tests.  We had a test where someone was placed in a isolated room with THC smoke was being pumped in for 24 hours straight and the person did not  register.  On a lab test it did pick up about 3 or 4 nanograms but as you know instant tests are set at 50ng/ml.”  Even at the confirmatory GC/MS lab urine drug test level of 15 ng/ml, you would still not test positive for marijuana due to second hand smoke.  

The cutoff level for the saliva drug test is 100 ng/ml (so again, second hand smoke would not produce a positive).  When it comes to hair, the manner in which the lab analyzes your sample makes external contamination impossible.  Hair drug testing labs only detect the metabolite of marijuana, THC-COOH.  This is only produced when marijuana directly enters the body (and not through someone’s second hand smoke, which is indirect) and is broken down by the body.  The hair test will not pick up contaminants from the outside.

And from yet another: It may concern anyone going on a job interview or visiting a probation department that he/she may or may not pass a drug test, especially after exposure to second-hand smoke.First, most nonsmokers have nothing to worry about. Second, marijuana smoke inhaled second hand, whether or not it produces a buzz, can leave traces of tetrahydrocannabinol (THC) in urine for about 1-2 days after smoke is inhaled, depending on body mass and activity. Third, most immunoassay drug tests, including standard EMIT, ELISA and RIA tests, are set at high thresholds intentionally to avoid false-positive results due to incidental ingestions of second-hand smoke. So the amount breathed in is not usually enough to produce a positive test. Next, the lungs do not filter THC out of smoke; they absorb it in small amounts. Smoke inhaled secondarily must infiltrate the lungs in heavy concentrations in order to produce clinically positive tests. Smoke exhaled by one person and inhaled by another or smoke that floats in a space may not contain the original high concentrations of THC; hence a small-to-zero likelihood that drug tests could read positive.Another point: tests for marijuana screen for THC metabolites; they do not test directly for THC. THC is fat-soluble and is released into the blood stream, exiting the body when broken down by liver enzymes via oxidation and metabolization over time. So, unless a urine sample is taken right at the time a large amount of THC is inhaled, a drug test should remain negative.

****So the consensus is NO, but if you are worried, stay away from people smoking dope, they can only entice you to engage also.


What About Other Drugs? How Long Do They Stay In My System?

According to a survey by Quest Diagnostics, 50% of all drug test positives are for marijuana. What about the other 50%? The table below shows how long drugs other than marijuana typically stay in your system:






Marijuana- Single Use 1-7 + days 12-24 hours Doubtful

Not validated.
Estimated 0-24 hours

Marijuana – Regular Use 7-100 days 2-7 days


Amphetamines 1-3 days 24 hours
Cocaine 1-3 days 1-3 days
Heroin, Opiates 1-4 days 1-3 days
PCP 3-7 days 1-3 days

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2 thoughts on “Can Secondhand Smoke Cause a Positive Drug Test for Marijuana?

  1. I was around a smoker outside i dont smoke i only smelled it then quickly moved away i took a drug test this morning will it come back positive.

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