Any cigarette smoker "licks door knobs", just indirectly, and inadvertently.. People touch the knob.. and then take cigarette to their lips using the same hands. I am not smoker, but as far as I know, the filter which people put to their mouths is the first thing that you see after opening a new cigarette box, and it's almost impossible not to touch it, to get out the rest of cigarette from the box. You must touch the filter... Yet another reason to quit smoking..   ps. The