Michael Lebowitz
Michael Lebowitz answered

Hair labs use extensive washing procedures that rinse out external contamination that might occur from 2nd hand smoke. These washing procedures are delicate enough to make sure that actual toxins deposited into the hair through the bloodstream are not washed away.

Read more here Hair Drug Test 2nd Hand Smoke

Rooster Cogburn
Rooster Cogburn answered N. Harmonik's question

I had an employee once that had one in his car after a couple of D.U.I.'s .I wouldn't let him drink any after work but he did tell me that another person could sit in his car and blow in it and start it and he could drive. I needed him at work and that's … Read more