A fog machine (also called 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.
Some fog machines use dry ice to produce a fog of small ice particles.
Uses of fog machines
A heavy duty smoke machine feeding smoke into a blower to generate fog effects for open air location filming.Fog machines are used to create spooky effects in plays such as Dracula, A Christmas Carol, and Macbeth. Fog machines are also frequently used in Halloween displays such as haunted houses or forests. Because of greater availability and reductions in prices between 2003 and 2005 , fog machines have become widely used for domestic halloween decorations.
Fog machines are also useful for industrial purposes, such as visualising the flow of air, such as over a surface in a wind tunnel or testing filters in air conditioning. Fire fighters also use fog machines in their training.
Because of the reflective and refractive qualities of the smoke created by fog machines, they are often used in nightclubs to enhance the effects of lighting and laser arrangements (see also light beam).
Adverse effects on respiratory health
A special effects engineer positions the inflatable plastic tube feeding the smoke.Although often believed to be safe to breathe, exposure to mineral oil, glycol and glycerin-based theatrical fogs produced from fog or haze machines have been associated with adverse short and long-term effects on respiratory health in exposed performers and crew members, especially those with respiratory problems (such as asthma). One should therefore avoid breathing generated smoke or fog. It is safer to add smoke effects digitally in postproduction of films than to use theatrical smokes on set. Glycol-based fog is associated with headaches, dizziness, drowsiness and tiredness in those exposed. These results would be expected given that glycols share some chemical similarities to alcohols and given the small size of fog particles making it easy for them to enter the bloodstream. Symptoms of wheezing and chest tightness were associated with longterm exposure to theatrical smoke and fogs.
Haze machines, or haze generators, commonly referred to as hazers, are similar to fog machines in that they produce droplets suspended in the air which are designed to make light beams visible.
Unlike conventional fog which can be dense enough to become opaque, haze is very thin. Ideally haze is barely noticeable, if at all, in normal lighting conditions. This allows the operator to fill a venue with haze prior to an event without creating a visibly distracting cloud.
Haze also has a substantially longer hang time than conventional fog. While conventional fog may hang in the air for up to 5 minutes, a typical water-based haze can last 1 hour and oil-based haze 6 hours or more, depending on the size of the venue and the amount of ventilation.
Some haze machines use a compressor to atomize a fluid (usually, though not always oil-based), therefore they do not require any warm up time. Other machines use a heater to vaporize the fluid (usually water-based). Most oil-based haze fluids use a mineral oil base, and most water-based fluids use either a glycol or glycerol base.
Hazers produce smaller particles in the air reducing the chance of particle sensor based fire alarm being activated compared to fog machines. The size or particles and effect varies by manufactures and fluid type used.
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