of course its on the internet so must take it with a grain of salt
""Second hand marijuana smoke in a car can cause you to fail the next day" (Nightbyrd). It is possible that second hand marijuana smoke will raise someone to the 50 ng/mL level; however, *extreme* exposure is required. For instance, a closed car full of pot smokers and a non-smoker may render the non-smoker positive for both urinalysis and the hair test, provided that they are sealed in the car for a while. The Army did a case study where volunteers were put in a room pumped full of smoke for an hour, five times daily. Subjects started testing positive after the second day. The non-smoker would have to take in virtually as much second hand smoke as a smoker. Non-smokers are safe in a ventilated area, as long as they don't get a hair test. According to Clinton, simply blowing crack smoke on ones hair may cause a positive hair test. Second hand pot smoke doesn't affect the hair test results as much as crack smoke does mainly because exhaled smoke contains no THC. The only pot smoke that contains THC is the smoke that hasn't entered the lungs."
"Once you've tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return."