Does Second Hand Marijuana Smoke Show Up On A Drug Test?

A commenter asked a great question on one of our older posts.  That question was, does second hand smoke affect the result of a drug test?  It wouldn’t be fair if it did, of course.  As the commenter points out, (medical) marijuana is legal in some states, and if you are not smoking it, you should not be punished for having been around second hand smoke.

The good news is that none of our home drug test kits (hair, urine, or saliva) will pick up exposure to second hand marijuana smoke as a positive result.  Here is what the test manufacturer said on the subject:

“It [second hand marijuana smoke] would not register on our 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.”

Does second hand marijuana smoke affect our drug tests?

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.

So, even if you have been exposed to second hand smoke, if you have not yourself smoked you should be safe with our tests.  Thank you to our readers for such great questions and I look forward to more in the future!


  1. Sam says:

    I’m trying to get a job at a place that does hair tests in May. In november or december when I was drunk I took one hit. will this show up?

  2. admin says:

    Hi Mom of Three,

    Unfortunately, I don’t know of any second hand marijuana test. Our tests are designed to exclude second hand smoke. You may want to ask your doctor or another health professional if they are aware of such a thing. Thank you and again, sorry!


  3. admin says:

    Hi Sam,

    If you are talking about marijuana, one hit would probably not show up on a hair drug test. That seems highly unlikely. Also, most employers who take hair from the head only go back 90 days anyway. So your use wouldn’t be reflected. If they were taking body hair, which goes back 6 months to a year, drug use from nov/dec would be an issue. But again, if you only took one hit, it is very unlikely it would show up.

    Thank you,

  4. Personnn says:

    Will just regular smoking come up in a sports physical ???

  5. Jason says:


    I have an NCAA drug test coming up in two days. I smoked one or two hits on New Years Eve, and was in a room about two weeks ago where they were smoking a pretty sizable amount. I figured it wont show up giving my last time i smoked was almost two months ago (which was only two hits) and hot boxing a room doesnt show up. I am just worried due to the fact my scholarship rides on this.


  6. april says:

    Are you positive it doesn’t show up in a drug test?

  7. Dr. Andrew says:

    Hello ,

    For second hand marijuana smoke to be in the body one must have had constant contact with the smoke exhaled by other users. Usually in a Urine drug test, the Cannabis concentration must be below 120 ng/ml if the person has been in contact with the second hand smoke in less than 1 month and half approx. if the person has been in contact for less than 2 months approx the reading should read anywhere between 20ng/ml – 50ng/ml. The saliva cut off level is below 100 respectively.

    Dr. Andrew

  8. stevez says:

    I Tested myself the night before and, I was negative. When i took the same test at the doctors they told me i was positive? I haven’t smoked anything in Five weeks’ So, why was i Positive? I’m Still Pissed off about this. also one thing that may have changed the outcome is the person that works for my doctor us to live in one of my homes’ her boyfriend and her stopped paying me the rent so,I had to evict them. does anyone know if i may have a lawsuit? thanks stevez

  9. stevez says:

    someone i know at a party blew thc in my face . two weeks later i showed up positive on the ur test. So, i went home haven’t Smoked anything. Five weeks go buy and i go in for a secound test. before i took the test i bought a thc test kit and checked myself the night before it was negative. I go to The Doctors the next day have the test there they tell me to wait in the room. the doctor comes back and tells me it’s positive. I Freekout Telling him i didn’t Smoke anything. He asked me if i was around anyone and i said yes but i wasn’t smoking. The doctor said he was sending out the sample to a lab. Now, i got home late today bought the test kit at walgreens took the test and it’s Negative? what should i do? Sould i go to a Labcorp and pay for another test myself? and send the results to my doctor? thank you for some advise

  10. Jlav says:

    It’s been 35 days since I’ve been around marijuana smoke. After 20days I took a home test and I got a faint pink line. That test was at 50ng. 15 days later I had to take a pre employment test and I believe it has a cut off level of 15ng. I have a fast metabolism and when I did smoke it was just one time and a small amount. It was 35 days clean before test. Will I pass at 15ng

  11. Jake says:

    I was about 10 to 20 feet away from my friends when they where smoking weed and I may have a drug test at any time to determine whether or not I get the job I need. It will be a urine test and I’m just a little worried so just PLEASE help!!

  12. Lcpl Adams says:

    Im a Marine based in 29 palms. I was a security guard at cochella fest this year. I worked security in the VIP tent from 9am to 3am. There was a constant flow of people smoking weed inside the tent. I started working on friday and the last day was sunday. I came back, and we had a piss test. I popped with a THC level of 36. Now I am going to court to fight it. Is there any legal or confirmed answer in regards to popping due to second hand smoke in such small quarters and for so many hours in a row? I look forward to your reply.
    call or email, whichever is convienent. Thank you very much for your time
    Lcpl Adams. 3/4 Kilo CO. USMCB

  13. John says:

    I haven’t smoked in over a year, and I just smoked 3 or 4 hits from a joint, and a have a drug test in 4 days, am I gonna test positive or will I be ok? I keep hearing different things, also I am in good shape, and thin so that’s less of a chance from what I heard.

  14. Brian says:

    Hi, my stoopid roommate smokes weed in doors just because he think he can. So my question is if I inhaled a secondhand smoke from him, and I have to take a urine test in four days what it show up in the military urine test? that I mean by MEPS

  15. Brian says:

    Let me just add that I have inhaled one or two hits from him secondhand smoking when he was in the living room.

  16. Jessie says:

    My husband is a regular smoker and he wants to pass a drug test soon the drug test will be a swab. How long should he wait to pass it?? And if I’m smoking does it effect him when we “make out”?? Thanks!!

  17. joe blue says:

    I took 1 hit the day before the doctors not a test for 6 months then there it was and yes i tested positive for pot. My roommate smokes a ton of it, so it is constantly in the house you tell me.

  18. donna says:

    My boyfriend smokes marijuana every day but I don’t but I’m in the same room with him can I test positive I have to take a drug test Tuesday

  19. johny says:

    I was in a car with windows down and my friends light up .25 grams of weed. i had my shirt over my nose n mouth till the smoke was cleared. i have a urine drug test in a week. will i test positive?

  20. D says:

    I was around someone that smoked and I went for a drug screen and it came out positive for Marijuana………….this is sum bull crap!

  21. Anonymous says:

    I am 5′ 10”, 270 lb , female, slow metobolism, daily smoker, how long to pass pee test

  22. crazy says:

    I had a urine test at a pain management clinic today and it came back positive for THC. I took a couple hits 5 weeks ago and none at all since April and the only time im around it is when my boyfriend is smoking it in the car.. Im thinking that the amount had to be low because they gave me my meds anyways.. Is it possible to have THC show up in your urine that long after you smoke that little? I am only 110 lbs.. How much do people have in hteir systems naturally?

  23. sany says:

    My bf smoke every day and I don’t,(mj), but I do b around him when he smoke! I stoped smoking a mt ago, my test was positive,so am I gonna get clean ever if I smell that nasty second hand mj smoke?

  24. FirstTimeSmoker says:

    I inhaled a little smoke from a bong, but only twice and I didn’t hold it for very long. This was the first time I’ve ever smoked anything and I’m fairly healthy. But I’ve heard that a bong is more potent than a joint. Is this accurate and does the same time line apply in this case or would it take longer to process out of my system?

  25. dee says:

    my husband smokes weed everyday morning on my way dropping him off at wk and when he gets hm im around him all the time when he does can thc show up in my system as if im smoking too?

  26. concerned parent says:

    I have a strong suspicion tht my Ex is smoking Marijuana around my kids. If I take them to a Dr. To have them tested will there be sufficient evidence to prove they are being exposed to secondhand marijuana smoke. What is the best test to give them?

  27. Candi says:

    I have a urine test coming tom morning and the last day I smoked was last sunday. I have been drinking alot of water and over this weekend I had some mixed drinks that made me urinate alot. I am worried about passing this test. What are the chances of me failing, and if I continue to drink lots of water will I have more of a chance passing my UA? When I urinate it is clear. I would greatly appreciate some feedback.

  28. marie says:

    I smoked 2 maybe three hits barely, a week ago. For the first time in a year- year and a half. I have a job interview in a week. Will it come up positive after two weeks of not smoking? What if I drink a lot of water from now tell the Test?

  29. Tgod says:

    Was and usually around marijuana second hand smoke in a small room but with a ventilation(fan) would I show positive on a urine test?

  30. […] Kitchen Some Google searches seem to confirm that second hand smoke will not sure up on a test: Does Second Hand Marijuana Smoke Show Up On A Drug Test? | Home Health Testing Second-hand marijuana smoke and drug tests | Go Ask Alice! The second one suggests that the […]

  31. Dawn whitt says:

    Im living proof you can test positive from second hand smoke!

  32. Kara says:

    I had to take a drug test yesterday, and I tested positive for THC, and I’ve never smoked a day in my life! I was around it a couple days before my drug test, but didn’t think it would register. Well, it did, and I was denied the position because of second-hand smoke! So I, as well as Dawn, are living proof you can test positive from second hand smoke!

  33. […] level of 15 ng/ml, you would still not test positive for marijuana due to second hand smoke.…n-a-drug-test/ __________________ Czech/Prague […]

  34. Joshua fender says:

    This is NOT true. I failed a instant test for thc and I dont smoke at all. Instant test will pick it up. DO NOT BE FOOLED BY THIS PUBLICATION. It is false, I am living proof that just being in the room is enough to fail

  35. tc253 says:

    i say it is true because i went to the probation office and failed a drug test the other day. they told me that i HAD to have smoked but i really havent. ive been in a few cars where it was being smoked though so i am also living proof that thc WILL be in your system even if you havent smoked

  36. Abby says:

    Hey! I’m not a smoker, but my parents do. I can tell when they have been because I can smell it almost emedietly every time after they do it. I got a drug test at school, and all of the bars were dark except for the Marajuana one… I’m sure you can sense my panic because I don’t smoke.. Nor have I injested any “special” foods. I passed my drug test because there was still a visible line, but it was very faint. Is it possible that my parents second hand smoke showed up in my tests? even a little bit?

  37. Ricky says:

    I am a medical marijuana smoker recently I got charged with a bogus charge and now am on pre trial services something like probation it has been 40 days since I last smoked. I dropped yesterday and now am being threaten with jail time, I really don’t know how that is even a fact. I weight 156 5’10 and workout every other day. Can you please tell me what’s up with that ? thanx.

  38. mike says:

    I was in a room where a buddy was smoking and i had to take a test the next day for my AODA program an they are telling me it came back possitive. Is this true?

  39. admin says:

    The intensity of the color of a line on the drug test does not mean anything and should not be interpreted as a measure of the amount of drugs. A faint line on a drug test is still a line, so if you have a faint line in the “T” area of the test then you have a negative drug screen.

  40. Bobby says:

    I was exposed to second hand marijuana smoke today and have a drug test tomorrow. The exposure was in a room where my friends smoked one joint and the door was open and the window was cracked. I haven’t smoked in 6 weeks and have passed a home drug test as well as a lab test a week or so ago. Do I run a risk of failing tomorrow due to my exposure?

  41. Andri says:

    My father and stepmother smoke around 7-10 joints in the house every day and I fear that I will test positive when I go to MEPS. The smell of it is disgusting and overwhelming and it makes very angry. When they smoke they have the windows closed but the a/c flowing, which pumps all the smell in to my room. Could I test positive from being in this situation?

  42. Mitch says:

    What about someone exhaling into your mouth, essentially transferring the smoke? I’m just curious, because what you exhale and the smoke being produced should be relatively the same, but I wonder if you would be able in intake enough thc for it to show up, even though its prob. enough to get you stoned.

  43. nicole says:

    Hey so I’ve been sentenced to a year of drug program by court order or I go to jail… question is this I’ve not smoked in bout week program is aware of the last day I smoked so they know it will take 3 to 4 weeks to leave my system…..I’m 40 been smoking regularly since I was 15 and now that I stopped I’m expected to be clean in a few weeks…….My boyfriend smoke everyday 4 to 5 times a day sometimes I’m in room with him will being around him and the second hand smoke effect the amount of time for the thc to pass out of my system please help I need to be clean in 3 weeks

  44. admin says:

    Research shows that THC lingers in your system for many weeks and if small additional amounts are added from second hand smoke it could make it take longer for it to fully leave your system. While it is difficult for a non-smoker to test positive from second hand smoke, that is not the case for someone who already has THC stored in their body.