Theatrical Fog Machine Safety: Operation, Maintenance, and Health Considerations
Theatrical fog machines and hazers are among the most commonly used atmospheric effect devices in modern performance. They are also among the least carefully managed from a safety perspective. Every technician who operates atmospheric effect equipment must understand the applicable standards, the health research, the specific hazards of different fluid and gas types, and the monitoring and ventilation requirements that apply.
Types of Atmospheric Effect Machines
Not all fog machines are the same. Understanding the type of machine and fluid is the starting point for any safety analysis:
- Water-based fog machines: generate a dense fog from a glycol-water solution (typically propylene glycol, triethylene glycol, or a mixture). ANSI E1.5-2009 (R2024) covers theatrical fog made with aqueous solutions of di- and trihydric alcohols.
- Hazer machines: produce a lighter, more diffuse atmospheric haze using mineral oil (oil-based haze) or glycol-water (water-based haze). Oil-based haze lingers longer but carries different health considerations.
- CO2 and cryogenic (cryo) systems: use liquid CO2 to produce low-lying fog effects. CO2 displaces oxygen and can create hazardous oxygen-deficient atmospheres.
- Dry ice systems: submerge dry ice (solid CO2) in hot water to produce dense, low-lying effects. Same oxygen displacement risk as liquid CO2 systems.
- Nitrogen-based systems: use liquid nitrogen to chill a water mist and produce low-lying effects. Nitrogen displaces oxygen.
Applicable ANSI Standards
ANSI E1.5-2009 (R2024): Entertainment Technology: Theatrical Fog Made With Aqueous Solutions of Di- and Trihydric Alcohols. This standard addresses product requirements for water-based theatrical fog fluid and fog generator products. It establishes fluid composition requirements that limit ingredients to those with known safety profiles.
ANSI E1.23-2020: Design, Execution, and Maintenance of Atmospheric Effects. This standard covers the broad category of atmospheric effects including fog, haze, and smoke in theatrical environments. It addresses design of effects, execution during performances, and maintenance of equipment. Key requirements include adequate ventilation during atmospheric effect use and limitations on effect duration in enclosed spaces with inadequate fresh air exchange.
ANSI E1.29-2009: Product Safety Standard for Theatrical Fog Generators That Create Aerosols of Water, Aqueous Solutions of Glycol or Glycerine. This standard covers product safety requirements for the machines themselves.
Health Research on Theatrical Fog
The health effects of theatrical fog have been documented in peer-reviewed research. Two foundational studies are widely cited:
Moline and Golden (2000) conducted a health effects evaluation for Actors’ Equity Association examining theatrical smoke, haze, and pyrotechnics. The study documented respiratory symptoms in performers and crew exposed to glycol-based fog and haze.
Varughese et al. (2005), published in the American Journal of Industrial Medicine, reported that exposure to theatrical smokes and fogs was associated with acute and chronic respiratory symptoms in entertainment industry workers. Workers with asthma were at particular risk. The study found that water-based fog was associated with acute upper and lower respiratory symptoms, while oil-based haze was associated with both acute and chronic lower respiratory symptoms.
These findings have informed both the ANSI standards and the policies of Actors’ Equity Association, which has specific agreements governing fog use in AEA productions including notification requirements and performer consent.
Fluid Safety
Only fluids designed and formulated for theatrical fog use should be used in theatrical fog machines. Never use automotive antifreeze, mineral oil not formulated for theatrical use, or improvised mixtures. The SDS for any fog fluid must be on file and available. Water-based glycol fluids are generally lower hazard than oil-based fluids, but the appropriate fluid for a specific machine depends on the manufacturer’s specifications. Using an incompatible fluid can damage the machine and change the aerosol characteristics in unpredictable ways.
CO2 and Cryogenic Safety
Liquid CO2 and cryogenic systems present unique hazards. CO2 is an asphyxiant: it displaces oxygen and in sufficient concentrations can cause unconsciousness and death without warning. CO2 is heavier than air and accumulates at floor level, making pit areas, orchestra pits, and below-stage spaces particularly hazardous.
OSHA’s oxygen-deficient atmosphere threshold is below 19.5% oxygen. An oxygen monitor must be present and operational whenever liquid CO2 or cryogenic effects are in use in enclosed spaces. If the oxygen level drops below 19.5%, work must stop and the space must be evacuated and ventilated before re-entry.
Dry ice handling requires cryogenic-rated gloves to prevent severe cold burns. Direct contact with dry ice causes frostbite within seconds.
Ventilation During Atmospheric Effect Use
ANSI E1.23-2020 requires adequate ventilation during atmospheric effect use. Mechanical ventilation is preferred over natural ventilation. The standard does not specify a minimum air change rate because the appropriate rate depends on the specific effect, the space volume, and the occupant density. The general principle is that atmospheric effects must not accumulate to the point where they impair vision to the exits, reduce oxygen levels, or cause respiratory distress to occupants.
Glycol-based fog can actuate smoke detectors. Before using atmospheric effects in a venue, the building’s fire alarm system must be coordinated with building management to determine which detectors may be affected, and a procedure must be established for managing alarm events during legitimate effects use without defeating fire alarm protection for the entire building.
Machine Maintenance
Theatrical fog machines require regular maintenance per the manufacturer’s schedule. Glycol residue accumulates in the heat exchanger, fluid reservoir, and output nozzle, reducing output quality and potentially creating conditions for bacterial growth in water-based systems. Manufacturer-recommended cleaning procedures must be followed. Machines that produce an unusual smell, discolored output, or reduced output volume must be taken out of service for maintenance.
Notification and Audience Consent
Best practice, and in some jurisdictions a legal requirement, is to notify audience members that atmospheric effects will be used in a performance. This allows individuals with respiratory conditions or sensitivities to make informed decisions. Programs, lobby signage, or pre-performance announcements are appropriate notification methods.
Key Takeaways
- ANSI E1.5-2009 (R2024) covers water-based theatrical fog fluid. ANSI E1.23-2020 covers design and maintenance of atmospheric effects.
- Oil-based haze has documented associations with chronic lower respiratory effects in entertainment workers.
- CO2 and cryogenic systems can create oxygen-deficient atmospheres. Continuous oxygen monitoring is required in enclosed spaces.
- Only manufacturer-approved fluids should be used in any atmospheric effect machine.
- Glycol fog can actuate smoke detectors: coordination with building management is required before use.
- Machine maintenance must be performed per manufacturer schedule to ensure safe operation.
- Audience notification about atmospheric effects is best practice and may be legally required.
References
Entertainment Services and Technology Association. (2024). ANSI E1.5-2009 (R2024): Entertainment technology: Theatrical fog made with aqueous solutions of di- and trihydric alcohols. ESTA.
Entertainment Services and Technology Association. (2020). ANSI E1.23-2020: Entertainment technology: Design, execution, and maintenance of atmospheric effects. ESTA.
Varughese, S., Teschke, K., Brauer, M., Chow, Y., van Netten, C., & Kennedy, S. M. (2005). Effects of theatrical smokes and fogs on respiratory health in the entertainment industry. American Journal of Industrial Medicine, 47(5), 411-418.
Moline, J. M., & Golden, A. L. (2000). Health effects evaluation of theatrical smoke, haze, and pyrotechnics. Mount Sinai School of Medicine and ENVIRON International Corporation.