Add delay to knock out gas (N2O) kicking in?

[Zafhset]

The effects of gasses is already pretty easy to invalidate with internals, you don't need to weaken it even further. N2O is also a bit rarer and not as commonly available as the other gasses.

the slight inconvenience of having to refill O2 (which is already super easy with O2 vendors and various cans) isn't a counter point - in the first place you should not be breathing off purely on internals.