if your in a room with a bunch of people who are smoking weed would you end up showing positive if you were drug tested.
There are several published studies that do demonstrate low level positive drug urine and blood drug tests after passive exposure to HIGH levels of marijuana smoke. This is one of those studies:
In this case, individuals who spent time in a small unventilated room in which 16 joints were smoked were found to have low levels of marijuana for short periods of time.
HOWEVER, this type of exposure is not really realistic to the claim that someone was accidentally exposed without their knowledge (since you would essentially have to be in a complete cloud of smoke). Multiple studies have been conducted with more realistic levels of exposure and they have NOT found positives with a more typical "passive" exposure above the threshold used in your test. This is the most recent of those studies.