It's impolite to smoke around a nonsmoking roommate.
John is sitting on the back patio with his roommate.
John wants to smoke a cigar.
John steps a good distance away from his roommate before lighting up.
John lights the cigar, and blows smoke in his roommate's direction.
Smoke goes nowhere near John's roommate and the two have a nice conversation.
John's roommate coughs and glares at him.