How do dive computers calculate nitrogen absorbtion and clearance when using nitrox?

[dmaziuk]

I've wondered if people ever do that--breathe O2 or Nitrox on the surface after a dive. Even if there's no easy way to calculate how much it shortens your required surface interval, it could add a margin of safety with repetitive dives that are pushing the limits.

Pulmonary toxicity doesn't go away, although at <40% O2 at 1 bar and healthy lungs it'd probably take days for any problems to develop. The interesting question is what if you're diving nitrox and breathing high % O2 at SIs for several days straight: do you really want to trade irritated lungs and lots of free radicals for some sub-clinical "decompression stress"? Which one takes longer to heal? Which one leaves less lasting damage?