Most pilots are annoyed if they are confined in the cockpit with a heavy smoker.

Some airports have smoking lounges, but some companies forbid you from using them (in view of the public). A few airports have places where employees can smoke, but flight crew usually don't have time to go find them between legs.

You can usually go outside security to the curb and smoke, unless you your company has the public view policy.

Alaska hires only non-tobacco users, and tests for it. Other majors will probably head down that road as the nation becomes more health-conscious (plus it saves bank on insurance). I have never heard of a regional refusing to hire smokers, but don't smoke or smell like smoke at an interview.