How sensitive is a standard drug test to cannabinoids?

There have been reports of second hand smoke (pive inhalation) of cannabis that resulted in detectable concentrations. While it is unlikely that THC or THC-COOH (metabolite) would be detectable in blood under such conditions 3 or 4 hours later, it might be detectable in urine (the ytical chemistry and biology of this is too complicated to explain here -sorry). Under most conditions though, casual exposure to smoked weed would not result in a positive tox screen. Lab studies that "push the envelop" on this are more akin to being in a car with several people smoking with the windows closed. Not exactly casual exposure. However, here is a good standard to apply. If the exposure was sufficient that you actually felt any kind of a high, the concentrations in your system is probably high enough to be detected. Hope that helps.