A fog machine or smoke machine is a device which emits a dense vapour that appears similar to fog

Fog

Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth's surface. While fog is a type of stratus cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated...

 or smoke

Smoke

Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...

. This artificial fog is most commonly used in professional entertainment applications

Theatrical smoke and fog

Theatrical smoke and fog, also known as special effect smoke, fog or haze, is a category of atmospheric effects used in the entertainment industry. The use of fog can be found throughout motion picture and television productions, live theatre, concerts, at nightclubs and raves, amusement and theme...

, but smaller, more affordable fog machines are becoming common for personal use. Fog machines can also be found in use in a variety of industrial, training, and some military applications. Typically, fog is created by vapourizing proprietary water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 and glycol-based or glycerine-based fluids or through the atomization of mineral oil

Mineral oil

A mineral oil is any of various colorless, odorless, light mixtures of alkanes in the C15 to C40 range from a non-vegetable source, particularly a distillate of petroleum....

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