I've never directly smoked. But, I grew up in a family full of very heavy smokers (that smoked inside the house). Growing up, I could never actually smell the stink of cigarettes and a lot of people thought I smoked too, because the smell was on me as well.
After I graduated high school, I moved away for school. I didn't realise that I was having trouble breathing until I was living in a cleaner air environment. Anytime I went back to my parents house, my lungs would feel heavy and my nose was really sensitive to the smell.
My step-dad developed asthma that was severe enough for him to be taken to the hospital and ended up getting prescribed a pretty heavy-duty inhaler.
My parents haven't smoked for about 3-4 years now. They quit when my step-dad had a heart attack. And since they've quit, he can use a normal inhaler now and he doesn't have to use it that often anymore.
They're house no longer has the smoker smell either, because they got rid of the old furniture (the couch was the worst) and cleaned everything.
(Now my only issue when I visit is itchy eyes and runny nose from the cat, but that will never stop me cuddling her, darnit!)