Last reviewed and updated: September 2025

The update and publication dates appearing at the bottom of this page are the dates when the content migrated to this website, not when it was last reviewed and updated.

This resource does not replace the Occupational Health and Safety Act (OHSA) and its regulations and should not be used as or considered legal advice. Health and safety inspectors apply and enforce these laws based on the facts they find in the workplace.

Overview

This guideline sets out some of the health and safety precautions employers and workers should take when using products and equipment that produce atmospheric effects, such as fog or haze, in a live performance event.

Fog and haze effects are used in many live performance venues and applications. This guideline was developed to help employers and workers:

  • understand and assess some of the risks associated with these products and equipment
  • plan their use so that they can be employed safely in live performance productions

Using products that produce fog or haze effects in a live performance presents direct and indirect hazards. Direct hazards can include:

  • respiratory impairment
  • chemical sensitivity issues
  • impeded vision

Indirect hazards can include:

  • contact with hot equipment used to produce fog or haze effects
  • slips and falls where fog or haze products produce a slick surface

While there are no specific requirements addressing the use of products or equipment used to produce fog or haze effects in a live performance production, the general duties under the Occupational Health and Safety Act (OHSA) and its regulations apply. Other legislation may also apply (see Resources).

What this guideline doesn’t cover

This guideline does not cover:

  • pyrotechnic special effects, including smoke cartridges, go to the resource section for details
  • flame effects, go to the resource section for details
  • real smoke caused by combustion
  • burning materials (for example, smudge, sweetgrass and incense) used for spiritual, religious or cultural ceremonies
  • smoking onstage (for example, herbal cigarettes and e-cigarettes)

Terms used in this guideline

This guideline uses several industry-specific terms. These definitions are provided for clarity and guidance only and, unless otherwise noted, are not definitions found under the OHSA or its regulations.

Atmospheric effects
A visual effect created by putting a liquid aerosol into the air of a theatre, motion picture studio or entertainment venue. (Source: ANSI E1.23 – 2020 “Entertainment Technology - Design, Execution, And Maintenance of Atmospheric Effects”).
Authority having jurisdiction (AHJ)
An organization, office or person responsible for enforcing legislation, a code or standard, or for approving equipment, materials installation or procedure. This includes the local fire department and the Technical Standards and Safety Authority (TSSA).
Competent person
Defined in subsection 1(1) of the OHSA as a person who:
  • is qualified because of knowledge, training and experience to organize the work and its performance
  • is familiar with this Act and the regulations that apply to the work
  • has knowledge of any potential or actual danger to health or safety in the workplace
Cryogen
A substance for producing low temperatures (source: Introduction to Modern Atmospheric Effects, 6th Edition), for example, dry ice, liquid carbon dioxide and liquid nitrogen.
Dry ice
Frozen carbon dioxide (nominal temperature –80°C), an effective cryogen (source: Introduction to Modern Atmospheric Effects, 6th Edition).
Fire watch
A qualified person or persons in attendance at all times when fixed fire protection systems are intentionally taken out of operation.
Fog
A mixture of liquid droplets in air that reduces visibility and reflects light (source: ANSI E1.23 – 2020 “Entertainment Technology - Design, Execution, And Maintenance of Atmospheric Effects”).
Glycol
A specific form of alcohol. The presence of glycol is clearly identified in most ingredient lists on the Safety Data Sheet (SDS).
Haze
An accumulation in the atmosphere of very fine, widely dispersed, solid or liquid particles giving the air an opalescent (shimmering or milky) appearance (source: ANSI E1.23 – 2020 “Entertainment Technology - Design, Execution, And Maintenance of Atmospheric Effects”).
Safety Data Sheet (SDS)
A technical document that summarizes health and safety information available about a hazardous product. It supplements the warning information on a label.
Smoke
Small, solid particles produced by burning and dispersed in the air. In the context of atmospheric effects, "smoke" is used to refer to any aerosol made of solid particles rather than liquid droplets (source: Introduction to Modern Atmospheric Effects, 6th Edition).

Rights and duties

The main purpose of the OHSA is to protect workers from health and safety hazards on the job. It sets out duties for all workplace parties, including employers and supervisors, as well as both duties and rights for workers. All workplace parties must know their general and specific rights and duties under the OHSA for creating, participating in, and maintaining safe workplaces. In addition, all workplace parties should make themselves familiar with the material contained in this guideline.

The Health and Safety Advisory Committee for Live Performance strongly encourages both employers and workers to follow these guidelines.

Event planning

The safety of the public, performers and production workers is important in all live performance events that include fog or haze effects. That’s why the following precautions should be taken:

Risk assessment

For a general overview of the risk assessment process, refer to Risk assessment for productions – Safety guidelines for the live performance industry in Ontario.

Areas of concern and risks to be assessed for the use of fog and haze are listed below

Exposure effects

The liquid and solid particles suspended in air to create fog and haze are inhaled easily and may cause irritation to workers. Some scientific research shows that low exposures to fog and haze are not hazardous to most workers. However, workers performing in very high concentrations of these effects can experience short-term irritation. Individual responses can vary, taking into consideration the degree of physical exertion (which affects respiration) during performance. As well, long-term exposure hazards have not been studied. Many products have been tested only for acute, short-term toxicity. See Resources.

Some products for producing fog and haze (such as glycols) are hygroscopic, meaning they absorb water out of the air. Others (such as mineral oil) stick to surfaces, creating a barrier preventing the absorption of water, pushing water away from the mucous membranes. Both types of products may cause:

  • respiratory and eye irritation
  • drying of the throat, nose and sinuses
  • minor irritation, which might go unnoticed by most workers, may leave some workers more susceptible to colds and infections and may affect vocal performance

Workers with an increased risk of irritation may include:

  • workers wearing contact lenses
  • workers with respiratory problems, such as asthma
  • workers with serious illnesses
  • children
  • pregnant women
  • elderly workers

Reduce exposures by:

  • placing fog or haze-making equipment to avoid exposing workers to a direct, concentrated release of fog or haze
  • limiting the amount of fog or haze effects used for a production
  • limiting exposure over the course of workdays in rehearsal

Child performers

A child performer’s exposure to atmospheric effects should be avoided. If fog and haze must be used, the child performer’s exposure should be minimized by:

  • limiting the time of their exposure
  • using the lowest concentration possible
  • using the least toxic or irritating product possible

Infant or child performers with respiratory problems, such as asthma or reactive airway disorders, should not be exposed to smoke or fog at any time.

Product selection and use

Select the least hazardous product with the most consistent method of production to achieve the desired visual effect.

Health factors

Consider health factors, such as:

  • workers with an increased risk of irritation (as previously stated)
  • strenuous physical activity, such as dancing, singing and playing musical instruments, since deep breathing increases inhalation hazards
  • length of exposure
  • position of the workers during the effect (for example, performers lying on the stage floor or musicians in orchestra pits when low-lying fog or haze is used)

If workers experience irritation when exposed to fog and haze effects, make appropriate adjustments to reduce the worker’s exposure, in keeping with what the worker needs for the performance.

Venue factors

Consider factors, such as:

  • venue rules regarding fog and haze effects
  • venue airflow patterns and ventilation
  • venue layout, including below-stage levels, trap rooms and orchestra pits
  • potential interference with building fire alarm systems (smoke and particle detectors) preventing proper detection of fire
  • skill of workers available to operate effects
  • appropriate and available storage facilities for dry ice, liquid carbon dioxide, liquid nitrogen, and others
  • outdoor exposure of the fog or haze machine to wet or freezing conditions

Product selection considerations

  • Consult the machine manufacturer’s instructions to ensure you select the appropriate product. Products have different formulas, and incompatible products and machines may cause ignition of the fluid or vapour, incomplete vapourization, or creation of toxic by-products.
  • Only select products for which a SDS is available with inhalation hazards listed.
  • Some suppliers do not provide the identity and proportion of ingredients to protect trade secrets. Products with SDSs that clearly identify the chemical ingredients should be chosen to better prepare for controlled exposure to the product.
  • Use only commercially manufactured products as directed by the machine manufacturer. Do not use a product that is “homemade.”

Due to toxicity and greater likelihood of respiratory irritation, the following substances or techniques should never be used to create fog, haze or smoke effects:

Smoke from combustion — smoke produced by burning frankincense, rosin, charcoal, tobacco, naphthalene or paraffin. Burning materials are irritating and generate carbon dioxide, carbon monoxide, and other toxic gases, vapours, and/or fumes. Exposure should be avoided.

Fumed inorganic chemicals — chemicals that emit smoke when heated, creating tiny airborne particles. The majority of smoke products of this type are chlorides, which are all respiratory irritants and should not be used.

Two-part smoke — acid and base smoke produced when two different chemicals interact. This method of producing a smoke effect is highly irritating and toxic. Although commonly used in small amounts by magicians, it should not be used to create fog and haze effects.

Training and information

Employers should inform all workers, including performers, when a production will include fog and haze effects.

For child performers, section 4 of the Protecting Child Performers Act, 2015 applies and there is an explicit requirement for employers to disclose to the child performer’s parent or guardian any health or safety hazards to which the child may be exposed during rehearsals or performances.

Workers should be encouraged to inform the employer of any concerns or medical conditions that could affect their participation in the performance, such as:

  • respiratory issues
  • allergies
  • chemical sensitivity issues
  • impeded vision

An employer must ensure that a worker who works with, or may be exposed to, a hazardous product is informed about all hazard information the supplier has provided about the product. These workers must receive the worker education required under Regulation 860 – Workplace Hazardous Materials Information System (WHMIS). This includes hazard information related to safe handling, use and storage of those products. Employers should make the product SDS available to workers and post it backstage.

Workers who operate machines must be trained on their safe operation.

Patrons should be notified that a production includes fog and haze effects, by posting a notice at:

  • the box office
  • all audience entrances
  • on the venue or show website

Safe work plan

Safe work plans create a structured approach to workplace health and safety at each stage of a production by ensuring that the training and information provided to workers incorporate:

  • the results obtained through risk assessments
  • the general and specific obligations under the OHSA

Before a rehearsal or performance

  • Store, handle and use products in accordance with manufacturer’s instructions and the SDS.
  • Do not alter products in any way. Do not add dyes, fragrances or additional chemicals.
  • Cryogens, such as dry ice, carbon dioxide, and liquid nitrogen, should be transported and stored in the container provided by the supplier or transferred to a suitable container. The container must be clearly labelled, and such labels must remain plainly visible. The handling and transportation of all compressed gas cylinders must meet the requirements of the WHMIS regulation under OHSA, Transportation of Dangerous Goods Regulations (TDG), the Technical Standards and Safety Authority (TSSA), and follow the information contained on the SDS.
  • Store products in a well-ventilated area. Allow space for stored cryogens to vent. As they warm, they become gases, which must be allowed to vent to prevent the container from rupturing.
  • Cryogens such as dry ice are extremely cold and must be handled with caution. Directly exposing skin to cryogens can cause severe frostbite.
  • Personal protective clothing and equipment such as gloves, long sleeves and eye and face protection must be used in the handling of dry ice. Exercise caution breaking dry ice into small chunks. If possible, use dry ice in pellet form.

Maintaining fog and haze machines

  • Maintain machines in good condition as required by the OHSA and the manufacturer’s instructions.
  • Ensure a rigorous maintenance and cleaning schedule for machines.
  • Machines must bear an electrical approval label accepted by the Electrical Safety Authority and must not be altered. To use a machine that is not approved, an electrical inspector must be called on site for a field inspection.
  • Do not bypass or modify the thermostat. A machine with malfunctioning temperature controls may allow combustion and toxic by-products may be created.
  • Beware of burn hazards due to boiling water used in some dry ice machines. Keep the lid tightly on the container and guard against splashes of hot water from the container.

Placement of fog and haze machines

  • Place machines in safe and appropriate locations in accordance with manufacturer’s instructions.
  • Machines should be in the control of a competent person at all times. They should be located where workers can safely access them, especially if located in an enclosed area, on a catwalk, within scenery or under a stage. They must not block emergency routes and exits.
  • Place the machines and their outlets well away from workers and traffic areas and protect against unintended contact with items such as moving scenery. The nozzle discharge may be extremely hot and can burn.
  • Avoid exposing workers to the direct output of fog machines. Concentrations are highest at the front of the machine. Never aim the nozzle directly at a person.
  • Never cover a machine with anything that impedes ventilation or is flammable.
  • Some parts on these machines get very hot. Be very careful when touching them.
  • As needed, place the machine on a spill or leak containment tray.
  • Appropriate fire extinguishers, as identified on the product SDS, must be located nearby.

Pre-event testing

  • Conduct pre-event testing to ensure critical visibility is maintained. Take steps to minimize the amount of spread into unintended areas.
  • Testing conditions should match actual performance conditions as closely as possible, including:
    • lighting
    • heating
    • cooling
    • audience presence
    • ventilation air flow
    • placement of scenery or workers that would affect distribution of the effect
  • For haze, monitoring during the event may be done in lieu of pre-event testing.

Preparing the effect

  • Deliver the effect only when and where it is required for the production.
  • Use the lowest concentration of product for the shortest period of time necessary to create the desired effect.
  • Avoid heavy exposure and minimize exposure during strenuous physical activity, such as dancing, singing and playing musical instruments.
  • Operate the effect equipment as instructed by the manufacturer.
  • Ensure measures are in place, as needed, to exhaust the stage, backstage and auditorium after the effect. Always exhaust away from the audience, orchestra pit and nearby technical or support areas.

Documenting the effect

Document the planned operation of the effect to describe the timing, output volume and duration of the effect. This will ensure consistent production of the effect each time and will make it easier to spot and respond to any changes that would suggest a developing problem.

During a rehearsal or performance

Variations in the effect may result from day to day fluctuations in weather, humidity and HVAC.

  • Monitor the visual effect during each performance to ensure it conforms to the desired effect
  • Operators should be prepared to make changes based on current conditions
  • Monitor airflow patterns during each rehearsal and performance to ensure the effect does not interfere with visibility of hazards, exit routes or warning signs
  • Track changes against the initial documentation of effect timing, output volumes and duration, to identify any developing problem (for example, an unnecessary increased use of fog or haze product, or the need for cleaning a machine that is not operating properly)

If someone has an adverse reaction

If someone has an adverse reaction to exposure, people should:

  • immediately remove the individual to a well-ventilated area
  • notify the first aid provider
  • follow the first aid instructions on the SDS

Monitoring and controlling exposure levels

When using a product that may cause an oxygen-deficient atmosphere to develop, monitor the amount of oxygen in the atmosphere and take immediate corrective action if necessary.

  • Never use dry ice in an enclosed space. When dry ice is plunged into water, a lot of gas is immediately released. This can cause oxygen deprivation, since cryogens, such as carbon dioxide (for example, dry ice and liquid carbon dioxide) and nitrogen, will displace oxygen.
  • Make sure the effect does not endanger workers, especially workers who may be lying on the ground where a chilled effect will be most dense.
  • Provide adequate ventilation, especially in low-lying and enclosed areas, such as orchestra pits, trap rooms and stairwells.
  • In addition to monitoring oxygen, it may be necessary to monitor carbon dioxide levels in these areas and alarms may be needed.

Product residue cleanup

Some products leave slippery or sticky residue on floors and can be tracked well beyond the area of use. Low-lying fog (for example, dry ice) often causes condensation and results in a wet floor.

  • Monitor and control any buildup of product residue and water on floors. Clean up carefully to prevent slipping hazards.
  • Take extra care with electrical equipment nearby to avoid shock hazards.
  • Monitor and minimize the buildup of product residue on theatrical lighting, projection equipment, electrical and electronics equipment, and the optics of fire alarm sensors.
  • Include a maintenance schedule to clean affected equipment frequently.
  • Ensure workers have appropriate footwear.

Interrupting fire protection and life safety systems for use of fog and haze

The disabling of fire detection devices within a fire protection and life safety system is prohibited.

Avoid the interruption of fire protection and life safety systems. When it is impossible to use fog and haze without activating the fire protection and life safety system, the system may need to be interrupted temporarily for the duration of the effect.

Automated alarms may be interrupted for the operation of fog and haze effects only when the following conditions are all met:

  • The AHJ and the building owner have both approved the interruption.
  • A fire watch is present. The fire watch should be familiar with and capable of directing the operation of all fire and life safety systems in the building and be able to notify emergency responders.

Fire protection and life safety systems that have been interrupted should be restored as directed by the AHJ.

After a rehearsal or performance

Immediately after each rehearsal or performance, the following steps should be taken to clean up and make the area safe until the next use:

  • clean up spills
  • clean any slip or trip hazards on the floor
  • check equipment for leaks or damage
  • shut down and secure equipment to prevent unauthorized or unsupervised use

Contact us

If you need more information, please contact the Health & Safety Contact Centre at:

Resources

Legislation

Related guidelines

Other resources

Resources from the ESTA Technical Standards Program (TSP). These ANSI standards documents are available for free download (e-mail sign in required).

  • ANSI E1.5 2009 (R2018) “Theatrical Fog Made with Aqueous Solutions of Di- and Trihydric Solutions”
  • ANSI E1.23 – 2020 “Entertainment Technology – Design, Execution and Maintenance of Atmospheric Effects”
  • ANSI E1.29 – 2009 (R2018) “Product Safety Standard for Theatrical Fog Generators That Create Aerosols of Water, Aqueous Solutions of Glycol or Glycerin, or Highly Refined Alkane Mineral Oil”
  • Introduction to Modern Atmospheric Effects, 6th edition, 2019
  • ESTA Fog and Smoke Working Group Reading List

Atmospheric Effects in the Entertainment Industry: Constituents, Exposures and Health Effects (2003) (a comprehensive study by the Workers’ Compensation Board of BC and the BC Lung Association)

Resources from the Actors’ Equity Association (U.S.)

  • Health Effects Evaluation of Theatrical Smoke, Haze and Pyrotechnics (June 2000)
  • Evaluation of Short-Term Exposures to Theatrical Smoke and Haze - Air Sampling Protocol (May 2001)
  • Equipment-Based Guidelines for the Use of Theatrical Smoke and Haze (June 2001)
  • Smoke and Haze Testing - Calibration Factors (December 2019)
  • Smoke and Haze Testing - Time and Distance Guidelines (December 2019)
  • Theatrical Smoke and Haze Report (May 2018)

Authors

This guideline was developed and revised by the following industry professionals on the Fog and haze sub-committee of the advisory committee for the Safety guidelines for the live performance industry in Ontario.

Current

  • Mark Fine, Air Magic Special Effects
  • Thierry Pouliot Fletcher, MDG Fog
  • George Galanis, IATSE Local 461
  • Alistair Hepburn, Alliance of Canadian Cinema, Television and Radio Artists
  • Doug Hook, IATSE Local 58
  • Steve Mosher, Canadian Federation of Musicians
  • Glenn Pringle, Canadian Registered Safety Professional (CRSP) Stage Manager
  • Janet Sellery, Sellery Health + Safety, Canadian Registered Safety Professional (CRSP)

Past (2005)

  • Jim Biros, Canadian Actors’ Equity Association
  • Rick Boychuk, Theatre Safety Consultants
  • Rob Gunn, Skydome
  • Peter McKinnon, Associated Designers of Canada
  • Steve Mosher, American Federation of Musicians
  • Bob Nicholson, Toronto Musicians’ Association
  • Shirley Third, CAEA Stage Manager