smokeless(a = adj.all) - emitting or containing little or no smoke; "smokeless factory stacks"; "smokeless fuel"; "a smokeless environment"
Antonym: smoky
Making or having no smoke. Pope. [1913 Webster]
smokeless, adj. having or producing no smoke.
Idiom:
smokeless zone a district in which it is illegal to create smoke and where only smokeless fuel may be used.