If you are switching from heliox to air for deco,there are far greater issues in your life than the miniscule chance of an ICD hit.
BTW what does all this have to do with the perception of narcosis?
In an earlier post, I suggested it would be a good test to see how narced one is by being on a helium mix then switching to air at depth to see the change. No one corrected me on this and I only discovered my error when I did a Trimix course and discovered Isobaric Counter Diffusion. Hence the link between the original post and the Isobaric Counter Diffusion discussion.
In hindsight not a test I would do or recommend.
"You don't know what you don't know until you get there, and often then its far too late"