A Smoker's Concentration

Today I saw a man smoking. It first caught my attention because I was annoyed because I was trying to eat and the smoke blew into my face. Then I started to look at him (kind of creepy, I know). His face would pull into concentration as he sucked on the cigarette. His brows drew down, slanting in towards his eyes, and his forehead would wrinkle. It was weird to notice his face turning into something that looked like concentration, but with smoking. I never thought someone would smoke with that much force, since I've always thought of it as more of a relaxing thing to do.