A fume or fumes refers to vapors (gases), dusts and/or smoke given off by a substance as a result of a chemical transformation such as reaction, heating, explosion or detonation. Fumes generally conveys the idea that the cloud is an irritating, hazardous and/or toxic substance. The term applies particularly to very fine solid particles as a suspension in air. This closely matches the definition of dust, the main difference being that fumes are airborne whereas dusts need not be suspended in the air.