Kalhoun,
Since you have not responded to my request on which part of my post you disbelieve I will have to guess.
I mentioned three aspects of smoking which have some effect on the aircraft.
I said that some part of the cabin air is re-circulated, on a modern Boeing (737,757,767) typically this would be 50%. This site illustrates how one modern aircraft, the B767 50% of air is re-circulated
http://www.forces-nl.org/vliegen/DOT/summary.html
“Data on nicotine exposures, cotinine (a major metaoblite of nicotine) excretion levels, and acute symptoms from a subsequent study of passive smoking on commercial airliner flights showed that a total separation of smoking and nonsmoking sections was not achieved (Mattson et al. 1989). The study was conducted with 9 subjects on tour flights lasting approximately 4 hours each. Two of the four flights were on aircraft with 100 percent outside air ventilation (Boeing 727) and the other two were on aircraft with 50 percent recirculation (Boeing 767). The observed nicotine levels were similar to those measured in the Oldnker and Conrad study: 13.6 +_ 23.0 ug/m3 in the boundary region of no-smoking sections and 16.5 +_ 7.1 ug/m3 in smoking sections. Aircraft with no recirculation had significantly lower nicotine concentrations than those with recirculation. Urinary cotinine levels were related to nicotine exposure for the subjects – those with the highest nicotine exposures had the highest levels of cotinine excretion. Eye and nose symptoms indicative of acute symptoms were related to nicotine and cotinine levels.”
As you can see it also backs up what I said about smoke, it does not recognise a non smoking area when it sees one and just barges right in. As you can see, the B727 has 100% fresh air ( or as fresh as air can be after some of it has passsd through the engines) but more modern Boeings (and other types) rely on re-circulating the air. Of course this means the air is filtered before being re-introduced into the cabin.
This brings me to the second point I made about nicotine contamination. First a cite.
http://www.house.gov/young/press/fs080289.htm
Senator Bill Young spoke about it:
“If you need proof that airplane ventilation systems are unable to adequately filter cabin air and if you really want to see what is in the air that is recycled for all airline passengers to breathe, I would encourage you to ask an airline to show you the filtering system of a commercial jet. Officials of National Airlines, prior to its merger, invited me to Miami to show me the inside of an airline ventilation system–a system that was so clogged with tar and nicotine that the maintenance crew was unable to get it clean. The residue clogging this system is indicative of the quality of air nonsmokers must breathe when confined to a small air space with smokers.”
It stands to reason that other components will be affected also (I mentioned a couple of those in my post) I spent some of my time rectifying those and many others.( For proof that I did, you would have to come over to my house and read my personal engineering records 
It’s different now with smoking bans on aircraft, but if you were to walk around the outside of a commercial airliner when smoking was allowed, and look at the skin and areas around door and hatches, you would often see the brown nicotine stains where the smoke had escaped via a slight leak from the pressurised cabin. My reason for mentioning both the effects of re-circulating the air and it’s effects on the airframe and its components was not to have a go at smokers, but to illustrate how airlines had to perform regular maintenance to keep the aircraft operating correctly.
What Constantine wrote amplifies what I have said.
“As long as we’re playing the “sit back and ask for a cite” game, do you have a cite for the proposition that “everything operated just fine” when people were smoking on airplanes? Do you have evidence that increased smoking did not increase maintenance costs, etc.? Vetch’s explanation sounds plausible to me. I don’t need a cite to an aircraft repair manual to be convinced that smoke does not do great things to either a pressurized ventilation system or a precision control system”.
If everything was fine then it was because of regular maintenance, and not because nicotine and tar didn’t have any effect on the aircraft and its components.
Finally, I assume you did not require a cite for my statement that cigarettes can cause fires.