Editing Fog machine (section)

==Types==

===Heated===
[[Image:Fogger Insides.JPG|thumb|Interior view of a fog machine, showing the pump and [[heat exchanger]].]]
Heated fog machines use either an inert gas or an electric pump to propel mineral oil, [[propylene glycol]], or [[glycerin]] and water mixture into a heat exchanger, where the solution is vaporized. The most commonly encountered form of heated fog machine is the pump machine. Very basic models of this type of machine consist of a fluid reservoir, an electric pump to move the fog fluid, and a heat exchanger, which vaporizes the fluid. More complex models may include a variety of other features, including variable speed pumps to control the output of fog, timer modules, or components for remote operation and monitoring of the fog machines' status. Some manufacturers have produced accessories and fluids that when combined with an ordinary heated pump machine, create fog effects similar to chilled fog machines.
Gas propelled fog machines use an inert gas (most commonly [[carbon dioxide|CO<sub>2</sub>]] or [[nitrogen]]) to propel either mineral oil or a glycol based fluid into a heat exchanger, where it is vaporized into particles, creating a fog. Some models of gas propelled fog machine provide control over the output of fog by varying the volume of gas used to propel the fluid.

===Chilled===
Chilled fog machines are designed to create thick clouds of fog that lie close to the ground and dissipate as they rise. They are typically created by using either [[dry ice]], compressed liquid {{CO2}},  liquid nitrogen, ice or more recently liquid air.
[[Image:DryIceMachine.JPG|thumb|right|Generic Dry Ice machine made from a 3G. drum.]]
[[File:DryIceSublimation.JPG|250px|thumb|[[Sublimation (phase transition)|Sublimation]] of [[dry ice]]]]
Dry ice (solid {{CO2}}) effects are produced by heating water to or near boiling in a suitable container (for example: a 55-gallon drum with water heater coils in it), and then dropping in one or more pieces of dry ice. Because at [[standard temperature and pressure]] carbon dioxide is a gas, the carbon dioxide sublimes and instantly produces a gas, condensing water vapor and creating a thick white fog. Liquid nitrogen (N<sub>2</sub>) can be used in a similar manner to dry ice. In either case, a fan placed at the top of the container directs the fog where it is needed.

Liquid air is an alternative to using liquid nitrogen in generating low lying fog effects. Liquid air is composed of N<sub>2</sub> and O<sub>2</sub> mixed in a ratio of 79% nitrogen and 21% oxygen stored as a liquid in insulated cylinders. This ratio of nitrogen to oxygen is the same as that of atmospheric air, and indeed liquid air may be fabricated by simply liquefying atmospheric air. Liquid air can be used as a direct replacement for liquid nitrogen in chilled-fog effects and is intended to be used in the same manner in the same equipment. Its key advantage over liquid nitrogen is that it presents no asphyxiation hazard, since it contains oxygen. A disadvantage is that it supports combustion, whereas liquid nitrogen inhibits combustion.