A fog machine (also calle a smoke machine) is a device which emits a dense vapor that appears similar to fog or smoke. This artificial fog or smoke is known as theatrical smoke and fog within the entertainment industry. Most fog machines create the fog by either vaporizing a water and glycol-based or glycerine-based fluid or a mineral-oil-based fog via atomization. For glycol-based fogs, the fluid (fog juice) is injected into a heated block, and evaporates quickly. The resulting pressure forces the vapor out of the exit. Upon coming into contact with cool outside air the vapor forms a fog.