I am a smoker. Recently my roommate was placed on probation. We live in a hotel room and I have continued to smoke with him in the room. I make sure the heat/ac unit is running and the fan in the bathroom. I also use a filter to exhale through. Due to the precautions I am taqking, could he still fail a drug screen?

Urine drug screens are usually not influenced by secondhand or sidestream smoke.

Hair drug testing is another story. It is very possible to obtain a positive on a hair test due to second-hand or sidestream burn of smoked drugs. (Most research involves marijuana).

Exhaling through a filter is probably beneficial as chemical residue attaches to clothing, furniture, etc and the content of crack varies by batch. No one knows how the elements could become incorporated into the body via external contamination.