LSI: Smoke Without Fire (February 1990)
[1.69Mb PDF]
From Lighting & Sound International

Safety Standards (including Material Safety Data Sheets - MSDS)

• 2009 ESTA standard on fog & smoke machine safety
• Martin MSDS coming soon

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Types of atmospheric effect

1. Dry Ice
2. Haze
3. Smoke / Fog
4. Low Smoke / Heavy Fog

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1. Dry Ice

Dry ice is frozen solid carbon dioxide which when placed into hot water sublimes into a gas and forms a thick white cold vapour which hangs low to the ground.
Dry ice is available in two main varieties – pellets and blocks. Pellets have a larger surface area, so produce a larger effect. A block will last longer, but won’t be as spectacular.

Handling

Due to it’s extreme cold, dry ice must only be handled wearing thick non-woollen gloves. Skin damage will occur if you touch dry ice directly. It goes without saying that dry ice must not enter your mouth!

Storage

Do not store dry ice in a freezer. The surface temperature of a block of dry ice is much lower than the freezer can maintain (minus 109.3 degrees Fahrenheit or minus 78.5 degrees Centigrade), and damage to the freezer may result. Also, dry ice should not be stored in an air tight container. As the dry ice sublimes, gas is produced which will cause a build-up of pressure, eventually resulting in an explosion.

The best way to store dry ice is in a polystyrene box with a loose fitting lid. The box should be packed with newspaper to help the dry ice keep itself cold.

Large-Scale Use

Long-running shows or those that require a large amount of dry ice often use Carbon Dioxide gas bottles to produce their own dry ice on site, on demand. This removes the wastage due to storage losses.

Danger of suffocation

As carbon dioxide is heavier than air, you must take care that any area lower than the dry ice machine cannot fill with carbon dioxide which If there’s more than 5% carbon dioxide in the air it can be toxic – suffocation will result if there’s an actor or technician in that environment.

Use

The dry ice effect is created on stage by immersing pellets or blocks of dry ice into boiling water. This is usually achieved by a Pea-Souper device (see video below), named after the London fogs in Victorian times.

Material Safety Data Sheet

• BOC Dry Ice MSDS

Suppliers

• Arctic Dry Ice (FL, USA)
• BOC (UK)

Video: Le Maitre Peasouper Dry Ice Machine

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2. Atmospheric Haze

Haze is designed to hang in the atmosphere, and to enable light beams to be visible. Striking effects can be achieved, as in this photo of Seneca's Oedipus at the Northcott Theatre in Exeter.

Many effects lights rely on the presence of haze to show up the beam, as the actual points of the stage which are illuminated by the light are not relevant - only how the beam looks travelling through the air.

Haze may disperse quite quickly, depending on the venue, humidity, air movement, and number of people present. Obviously an air conditioning system will remove it much faster.

Haze first appeared around 1989 as 'Cracked Oil Smoke Machines' or 'Crackers' - among the first units were 'Cirrus' made by John Coppen of Samuelsons Concert Productions. The early machines produced a thin white mist of airborne oil. Units made by Reel EFX in Hollywood use on-board compressors, but Cirrus used an external compressor, which could be sited at a considerable distance, or event outside the venue to reduce noise. (see LSI issue 40). 
INFORMATION TO FOLLOW about ill-effects from mineral oil crackers. 

There are now a number of different options for hazers, based on volume of haze produced, dispersal time and noisiness of the machine. As with all such things, you get what you pay for, so beware of choosing the cheapest option. If you can hire a machine to try it out first in your venue, that's usually the best bet. Hire companies won't stock unreliable or uneconomical machines, so if you can't hire it, use that as an indicator.

Circulating Haze

A desktop fan can be used behind a haze machine to disperse the haze and get it to where it's needed. The range of compact fans by Vornado are recommended. 

Don't use the fan in front of the haze machine, as it will get clogged up with haze fluid and the fan motor will be damaged, and the fan blades will need cleaning. Put the fan behind the machine to distribute the haze as it flows out. 

Examples of Haze Machines