Nick, Its probably just office gossip, you've probably been talked about... testing the water I would say, don't worry about it, unless your appearance is questioned again...
Smoking at work is something I hate, cant stand to be served in a shop by someone that had just nipped out on fag break, I also hate to see employees standing out the back of the building having a "smoke" I would also object, if I was a non smoker, to other smoking employees getting preferential treatment, and the benefit of extra ciggy breaks! I have found that smokers in general, see that theirs nothing wrong with this practice... and honestly, If I had my way, I would ban smoking at work entirely!
I also know of more than a couple of cases, where people have gone to job interviews, and not been given the job because they smell of smoke!
Socially, I have absolutely no problem with anyone smoking, and I will never raise the subject, or, other than this thread, give my opinion...
Nothing personal.
Thom