Theatrical smoke or haze is used to enhance lighting effects in concert halls, theatres, and television and film production.
The most common form of theatrical smoke is made by using a fog machine to heat a liquid (commonly known as fog juice). The liquid contains an oil that when heated to a sufficient point produces smoke. The fluid is pumped by the machine into a temperature controlled heat exchanger that vaporizes the fluid into thick clouds of fog, projecting it out through a nozzle located at the front of the machine.
The exact type of effect varies from a haze to an intense smoke depending on the machine used and the fluid used. Lighting designers and technicians are usually responsible for when and how these machines are deployed.
The particles that make up the fog are very small, 1 to 2 microns in size.
Fog machine fluids are usually a mixture of propylene glycol, triethylene glycol, and water.
Although often believed to be safe to breathe, exposure to mineral oil, glycol and glycerin-based theatrical fogs have been associated with adverse short and long-term effects on respiratory health in exposed performers and crew members. Audience members usually only suffer short term effects. Smoke can cause eye, nose and throat irritation. Some people have reported headaches, dizziness, drowsiness and tiredness.
Symptoms of wheezing and chest tightness were associated with longterm exposure to theatrical smoke and fogs.
For people with respiratory issues (such as asthma), theatrical smoke exposure can cause problems.
These results should 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.
Propylene glycol is known to cause health problems. It is well known to be a strong skin irritant. In the skin and hair, propylene glycol works as a humescent, which causes retention of moisture content of skin or cosmetic products by preventing the escape of moisture or water. This means that the deeper layers of skin are dried out. Propylene glycol can also cause liver and kidney problems if quantities are absorbed into the body. Triethylene glycol is similar in effects.
Theatrical smoke is absorbed into our bodies through the skin and through the lungs. The effects on our bodies is dependent on the level and length of exposure. Those who study the effects of smoke consider the effects at peak exposure and the time weighted average.
There is no doubt that theatrical smoke is a toxic substance and must be dealt with carefully. The industry position is that the use of machines in good working order, the use of approved fluids, and operation of the machines within industry guidelines is unlikely to have any permanent effect on individuals, unless they are known to be in risk categories. Some health professionals consider the exposure to any toxic substance will have some effect, suggesting that the overall impact is determined by the combined exposure to other toxic substances.
"Mineral oil- and glycol-based fogs are associated with acute and chronic adverse effects on respiratory health among employees. Reducing exposure, through controls, substitution, and elimination where possible, is likely to reduce these effects." "Effects of theatrical smokes and fogs on respiratory health in the entertainment industry". American Journal of Industrial Medicine 47 Issue (5): 411-418. Article by Sunil Varughese, Kay Teschke, Michael Brauer, Yat Chow, Chris van Netten, Susan M. Kennedy.
In the United States, the current, widely recognized exposure limits for fogs, smoke effects, and hazes, and other atmospheric effects using glycol, glycerin, and mineral oil are the following:
Glycol: 40 mg/m3 peak (1)(4)
10 mg/m3 time-weighted average for an eight-hour period (4)
Glycerin: 50 mg/m3 peak (3)(4)
10 mg/m3 time-weighted average for an eight-hour period (3)(4)
Mineral oil: 25 mg/m3 peak(1)
5 mg/m3 time-weighted average for an eight-hour period (2)
(1) Recommendations from Health Effects Evaluation of Theatrical Smoke, Haze, and Pyrotechnics, by researchers from the Mt. Sinai School of Medicine and ENVIRON International Corporation for the Equity-League Pension and Health Trust Funds. These guidance levels have been accepted for use in contracts between Equity and the League of American Theatres and Producers.
(2) OSHA regulations 29 CFR 1910.1000
(3) Recommendations from Theatrical Haze and Fog Testing for Mamma Mia! Winter Garden Theatre, by researchers from ENVIRON International Corporation for Mamma Mia! Broadway and Nina Lannan Associates. These guidance levels have been accepted by Equity for use on the Broadway production of Mamma Mia!
(4) ANSI E1.5-2003, Entertainment Technology - Theatrical Fog Made With Aqueous Solutions of Di-and Trihydric Alcohols
Performers and stage workers are likely to exceed the safe peak limits, particularly if they are in close proximity to the output of the smoke machine. Industry requirements in many countries require the monitoring of smoke levels and the implementation of occupational health and safety practices to minimise toxic exposure. In some countries, employers are obliged to advise employees of safety risks and exposure procedures. The New York Center for Safety in the Arts has noted many stage actors complain of irritated throat and lungs, respiratory problems, including occupational asthma due to exposure to theatrical smoke. A survey in 2000 of opera employees by the California Department of Health Services, found that 24 percent reported respiratory symptoms from exposure to theatrical smoke or fog
Audiences are less likely to exceed safe peak limits provided the machines are correctly positioned in stage areas and adequate ventilation is in place. In a number of countries, venue operators are obliged to advise audiences by displaying warning signs at the entrance to events and providing warnings on/or with tickets.
Person exposed to theatrical smoke should immediately wash the affected area with water if they experience any irritation or discomfort.
Whilst there is no long term evidence of adverse health effects from glycol based theatrical smoke, there is also no evidence of its safety as there is a lack of long term studies. Our best advice is that it should be avoided if possible. Glycols are a mild toxin and it certainly can be of no benefit to the body to be in contact with these substances. Daily life for most people already involves exposure to many pollutants, so we consider that people are better off avoiding any exposure which may increase their toxic load.
We do note that there are a number of well known performers who will not work with glycol based theatrical smoke due to the effects it has on their singing voices and ability to perform. That is probably the best position to adopt.
The other main method of theatrical fog involves using dry ice (frozen carbon dioxide). When exposed to water the dry ice releases carbon dioxide and water vapour. There are two main dangers with this method. The first relates to the handling of the dry ice which can cause severe burns if contacting skin akin to frostbite. The second issue relates to the release of the vapour. The fog has very little oxygen, and so can cause breathing difficulties for people who are covered by the fog. It is possible to die of suffocation. Usually the fog will lay low on a stage, so performers are normally breathing above the fog. Performers should never lie down in the fog. As the fog is heavier than air it will sink to the lowest point. Fog has affected stage hands, musicians in an orchestra pit, and audience members close to a stage when it has been used in an uncontrolled manner.
Sunil Varughese, MSc 1, Kay Teschke, PhD 1 2, Michael Brauer, ScD 1, Yat Chow, MSc 1, Chris van Netten, PhD 1 2, Susan M. Kennedy
School of Occupational and Environmental Hygiene, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
BACKGROUND: Theatrical fogs (glycol or mineral oil aerosols) are widely used in the entertainment industry to create special effects and make lighting visible.
METHODS: We studied 101 employees at 19 sites using fogs and measured personal fog exposures, across work shift lung function, and acute and chronic symptoms. Results were also compared to an external control population, studied previously.
RESULTS: Chronic work-related wheezing and chest tightness were significantly associated with increased cumulative exposure to fogs (mineral oil and glycols) over the previous 2 years. Acute cough and dry throat were associated with acute exposure to glycol-based fogs; increased acute upper airway symptoms were associated with increased fog aerosol overall. Lung function was significantly lower among those working closest to the fog source.
CONCLUSIONS: Mineral oil- and glycol-based fogs are associated with acute and chronic adverse effects on respiratory health among employees. Reducing exposure, through controls, substitution, and elimination where possible, is likely to reduce these effects. (c) 2005 Wiley-Liss, Inc.