In answer to your first question I assume you mean the 'blowing off' of carbon Monoxide (CO).
CO is a product of incomplete combustion of any flammable product, and is what kills you in gas/exhaust/fires.
CO is bound more strongly to haemoglobin (Hb) than oxygen, and displaces it from same. When the source of CO is removed, it takes some time for the CO to be removed, but a measurable effect on Hb-CO levels could theoretically be seen after 20 minutes (but unlikely). Once you are again exposed to CO, then you bind up your Hb, until it is able to unload it again.
It takes ~ 240 minutes for half of the CO bound to Hb to be eliminated, in room air.
Smokers can have up to 10% Hb bound to CO. Death usually occurs from ~>40% Hb binding.
As for your lungs, I can sometimes tell if someone once smoked by listening to their lungs, and the changes that occur on XRay are generally permanent.
About half of long-term smokers (and a significant proportion of social/2nd. hand smokers) will suffer from chronic changes of smoking (emphysema, cancer etc).
Once the damge is done to the lung, it is irreversible.
Some good news though - if you stop, then then damge need not progress, and from a heart point-of-view, your risk of heart attack and stoke rapidly decrreases.
Hope this helps. Try and keep off the evil weed.
RD.