I might be weird, but I’ve never air tested my Nox 600.
I learned from my other detectors that there is no perfect detector in every one of the possible configurations I could create, so I chose to not learn any shortcomings that it might have. I just get out as often as I can and am thankful for the great performance of the machine. There is so much that is positive with these machines, that to vilify a machine for something that was a man made scenario, is nit picking at its finest. Perhaps those chastising the machine for not being able to do something they may have expected it to do, would consider having their spouse do an exhaustive evaluation of said spouse's expectations of them when they first married, then voice those deficiencies on social media, while ignoring all the positive traits of the critiqued spouse.
To focus on deficiencies while ignoring the positive attributes is a recipe for disaster in any relationship...human or with a machine. You’ll always be thinking that you’re going to miss something because your self inflicted scenario that may or may not ever occur for you. You need to sell me your machine for $100 and go buy a machine that will meet your created air test scenario. Otherwise, you’ll always have that "what if" floating in the back of your mind.
I might go $150 if the machine is clean...after all, it’s already proven defective.