it depends on the standards of the lab
like some labs only test for a certain level of THC but many employers are asking for more stringent testing so the permissible amount of THC allowed can be lower than the lab's normal standard.
I remember this from when I was screened almost 2 years ago.

Granted you would have to be stuck in a hotbox to inhale that much THC but depending on who's doing the testing, it might just be enough to come back with an "inconclusive" result which opens you up to further testing.