If you must smoke and fly without O2 try and refrain from doing so for a few hours prior to the flight as it will aid your body in eliminating the CO
I always thought that the bond between Hb and CO was so strong that the CO was, in effect, never released again from the Hb molecule, rendering that molecule effectively useless for oxygen transport. Until the Hb molecule is regenerated in the body - something that happens, on average, every three months. That's why it may take victims of CO poisoning up to three months to recover fully.
So by what mechanism does smoking inhibit oxygen transport, in addition to the above? And does that effect really wear off in a few hours?
I'm not a smoker (and don't intend to become one) but I'd think that if you're addicted to smoking it's better to have a smoke just beforehand and do the flight reasonably relaxed, than not having a smoke just beforehand and suffer from withdrawal effects the whole flight.
Edited: Just read the Wikipedia article and it seems the half-life of HbCO is about 320 minutes instead of the three months I believed it was. So yes, this advice makes perfect sense to me now.
Carbon monoxide poisoning - Wikipedia, the free encyclopedia