They test you for tox where you are?
Harsh man, harsh.
Unless there is a stipulation that you cannot hang with guys who puff pot than you should be fine with smokin it.
Here anyway( canada) a positive tox screen for pot is not considered proof of consumption if you counter with a claim that it is second hand smoke.
haha remember the olympics?
Also it depends on what method of test they are gonna use.
Blood, urine,hair, all hold traces at different amounts for different lengths of time.