What happens when your next to someone that's smoking weed?

you should be fine dude. Unless your in an extremely smoke filled and i mean filled car if its even a small room you wont even feel a buzz. When people smoke weed they hold it in a long time so all the THC gets absorbed into the lungs, its very concentrated. So basically you will be fine unless there's more smoke than air in the room and rooms have vents that bring in and pull out air. the only way i could see it happening is in a closet or something and even then they would have to smoke allot and you would have to be in there a long time.