Can you get a second hand high?

Yes, you can.

Someone was smoking pot in the middle of class?
Contact high is possible, but I’ve never had it occur. And I’ve hotboxed many cars and a sauna (specifically meant for pot smoking).

How many people were smoking weed in the class at the time?

Yes, you are affected by those fumes.

Highly unlikely to get contact high. Like cash, ive been in quite a few Jamaican saunas without smoking and well, felt nothing. Where the hell was the person who was smoking?

I’m not sure where I got it, it just happened out of nowhere

If no one was smoking in the room then you couldn’t possibly get high.
Maybe it was your asthma?

Sounds more like an anxiety attack, since you weren’t actually near anyone smoking pot.

Unless someone offered you a brownie during lunch, you weren’t high. To get high without actually smoking, you’d have to be in a room filled with burning weed for a long, long time.