When I was in the RAF, we all smoked - all the time (at least the vast majority of us). I well remember the case of the C-130 Nav who set fire to his oxygen mask. (I was flying Argosys in Bahrain at the time). Said Nav decide that he was tired and decided to have a bit of 100% oxgen before top of drop to perk himself up. He then decided to have a fag but didn't turn the mask off first! The inevitable happened and a fast emergency descent into Muharraq was made. It took the fire brigade three hours to extinguish the mask (I expect that this was how long it took the oxygen to run out).
I also remeber one of my Navs telling me a story about flying on his first trip on a Lincoln squadron. The captain was either Polish or Czech but he had modified his H Type oxygen mask by taking the vent plug out so that he could stuff his pipe through the hole and carry on smoking whilst at altitude!
We were certainly dedicated in those days.