Originally Posted by u-Bob

Think again. Last Saturday I went to my brother's place. He doesn't smoke, his girlfriend doesn't smoke and he doesn't allow anyone to smoke inside.

The first thing I noticed and one of the first things I said: "A smoker has been here". And I was right. About 5 hours earlier one of his mates, a guy who smokes, came to visit him. The guy never smoked inside the house but he did sit on the couch for about an hour, talked, had a drink and left.

So 4 hours after the guy had left, I could still smell that he had been there.