Oooor... 1) You realize hydroponics has nothing to do with growing pot. 100 % of pot growers breath air. You don't use that to single them out. 2) You make su

Oooor... 1) You realize hydroponics has nothing to do with growing pot. 100 % of pot growers breath air. You don't use that to single them out. 2) You make sure the tested substance is actually pot. No test can be perfect, but it can be a LOT better than "sometimes it works". 3) You don't pretend you are military. Just knock the door, have chat with the white couple instead of pushing their face into the floor, pet the dog instead of shooting it, and have a look around for the pot growing operation instead of searching the entire house for something else.