Contact highs are horse shit. You'd have to be locked in a very small closet with ten people smoking weed at a ridiculous pace to get high from second hand smoke.
In my youth I got a DUI and the first thing my PO told me? If you smoke weed you better stop,and dont try and say it was second hand smoke. So if weed cant be detected in a drug screen from second hand smoke it surely not enough to get you high.
Adding to that,during my probation period I didnt smoke pot yet I was around it a lot and never got a contact high and never failed a whiz quiz.
So yes,contact highs are horse shit.