Smoke/Haze/Fog Machines

Smoke, fog or haze machines have long been used to maximize the effect of lighting effects, as most modern lighting effects rely on beams of light moving around. This effect is hugely enriched when the light hits the smoke or haze particles, making the beams more pronounced and visible.

There are generally 2 common ways in which fog effects are produced in stage productions. The first is to use equipment that utilizes the properties of “dry ice”, however the more practical and popular option is to use a fog machine that uses a specially manufactured water based fog fluid or fog “juice”, these are often referred to as smoke machines as the effect often looks like smoke however these machines do create liquid droplets as in fog not smoke which is made up of dry particles, consequently I will refer to them as fog machines.

Dry Ice:
One method of producing thick fog is through the use of “dry ice”, generally available from ice manufacturing plants and is relatively inexpensive to purchase. Dry ice however is difficult and dangerous to handle, transport and store and great care is required to avoid contact with unprotected human skin. This means that protective clothing, heavy duty gloves, must be worn at all times when handling it. Dry ice can also only be used in well-ventilated areas, and can pose problems whilst transporting it. Although, the effect can be quite interesting, commonly seen in old horror films, dry ice has many disadvantages that mean the fog machines will be appropriate for my project.

Fog Machines:
The basic operation of a fog machine is to heat the fog fluid or juice in order to create fog. Fog machines use a fluid sometimes referred to as fog juice that is pumped into a thermostatically temperature controlled heat exchanger that vaporizes the fluid into thick clouds of fog. The fluid is a mixture of pharmaceutical grade propylene glycol, triethylene glycol and distilled water that is mixed by the manufacturer, often specifically for their own machines.

All fog machines require a warm up period when switched on generally around five minutes. This can act as a problem, especially amongst budget products. As although they will generate fog for a short period they will then need to pause to reheat before they can make fog again. This is generally a continual automatic cycle during their operation. More expensive models, however, can generate fog continuously without the reheat cycle in between, meaning that there aren’t any gaps in fog distribution. The wattage (power rating) of the heating element in the machine can be a good indicator of how well a fog machine will perform. Most budget fog machines generally range from 400 to 1300 watts. With a higher wattage rating the fog machine can not only produce more fog but equally as important it will not have to go into a re-heat cycle as often because the heat exchanger has more power available.

Most fog machines come with a remote control either in the form of a simple single push button on the budget machines or a remote timer controller in the more expensive machines. From this the volume of fog can be controlled as well as operation duration timer and rest duration timer, allowing the user to set intervals at which the fog will be distributed, volume, thickness or the duration.

Fog machines make some noise while then they operate, usually produced by the pump as fluid is pumped from the reservoir to the heat exchanger. The fog expanding out of the nozzle can also produce enough sound, which is something that should be considered whilst choosing a machine.

Haze Machines:
Although the most common machines on the market are fog, there is also another option that has been popular in the theater for several years, haze machines. Haze machines combine a low output auto cycling fog machine with a small chamber containing a fan, which can produces much the same effect as a fog machine, but is far less obtrusive.

The major difference between a fog machine and a true haze machine is that a fog machine vaporizes the fluid with heat and a haze machine does it in a compression chamber without heat. In a fog machine, the fluid is pumped through the heater core where it vaporizes and is forced out the front in it's vaporized state. When the temperature of the heater core drops below the temperature necessary to vaporize the fluid, the pump is disabled so you can't shoot out hot liquid on the crowd. A fog machine also creates low-lying fog that usually doesn't go above your knees

In a haze machine, however, the fluid is pumped into an enclosed chamber where an air compressor (similar to what you inflate your tires with) blasts the fluid into a vapor, which is then blown out by a small fan in the form of a vapor. A haze machine never shoots out a thick cloud like a fogger can. In fact, you rarely see haze in the air. A hazer generally uses mineral oil and creates a fine haze that hangs for long periods of time in the air. It is a cold process as there is no heat involved. This sounds like it would be more suitable to use with the PIR detectors, as the fog produced by a fog machine will be warm and may set the PIR detectors off. There is a worry that a haze machine will produce cold vapor that will also set the PIR off, but as it is finer it is more likely to work. I would also prefer an effect that can relatively unnoticed, as I want the columns to appear solid and still, something that will be ruined by clouds of swirling fog.

Health and Safety:
There is currently no published research that suggests that there are any side effects on people’s lungs from fog produced by Glycol/water based fluids. It is generally accepted that sometimes the fog produced can cause problems for asthmatics, however nothing has been proven conclusively and due to the nature as asthma it is possible that symptoms could be psychosomatic. I will be sure, however, to tell the users before they enter the space that a haze machine will be used. I imagine that the users will only be in the installation space for a maximum of five minutes, which will further reduce the possibility of irritation.

The particles produced by fog machines will set off ionization type smoke detectors. Generally this is only a problem with ionization or optical type detectors as they sense the fog particles as smoke. I will be sure to check the studio space before using a haze machine, but I am confidant that there will not be a problem.

I have researched into different machines and have arrived at a few possibilities for machines. I will, however, be hiring the machine so it will depend on what haze machines the hire company have.

Possible Machines:
Smoke machine - High End F100 or one of the Antari line
Hazer - DF50, Star Hazer or Antari HZ400