Ideally singers would not smoke. In the real world, if you smoke you simply have to make up for it by working the body harder, to make the lungs do the better job they would if you didn't smoke, and your throat weren't being constantly dried out by the warm smoky air. Phlegm build up is also a problem smokers face. The solution is greater effort in opening the throat so the mucus can drain into the oesophegus.

This advice also works for singers with colds or chest infections.