The Air Your Performers Breathe Just Got Regulated. Here Is What Changed. – Expanded Version
Actors’ Equity’s 2024 fog and haze overhaul is the most significant update in over two decades. If you produce, design, or manage theatrical productions, this affects you now.
Every lighting designer knows the feeling. The haze catches a side-light wash just right and the whole stage becomes three-dimensional. Fog rolls across the deck during the storm scene and the audience holds its breath. A single beam of light cuts through a column of haze and the entire house understands the story in a way that words alone could never communicate.
Atmospheric effects are among the most powerful tools in our visual vocabulary. They are also one of the least understood from a health and safety perspective, and one of the most inconsistently regulated elements of theatrical production in the United States.
That just changed.
In 2024, Actors’ Equity Association completed its most comprehensive overhaul of smoke, fog, and haze regulations since the foundational Mount Sinai study was released in 2000. Updated Time and Distance charts, revised calibration factors, and clarified compliance expectations are now baked directly into current Equity contracts, including the 2023 to 2027 LORT collective bargaining agreement (Actors’ Equity Association, 2024a; League of Resident Theatres, 2023). This is not a subtle policy tweak or an incremental refinement. It is a rewrite of the operational framework that governs atmospheric effects on every Equity stage in the country.
If you are a production manager, technical director, master electrician, lighting designer, special effects technician, or producer working under any Equity agreement, this affects you directly and immediately. If you work in non-Equity theatre, educational theatre, or the broader entertainment industry, these changes will ripple into your world as well because Equity’s standards function as the de facto industry benchmark alongside the ANSI standards maintained by ESTA.
This article is a comprehensive guide to what changed, why it changed, what the science says, and exactly what you need to do about it. It is designed to serve as both a reference document for your technical team and a strategic planning resource for your production office.
What This Guide Covers
A Brief History of Theatrical Fog and Its Regulation
The desire to fill a performance space with atmospheric haze is as old as theatre itself. In ancient Greece, performers and technicians used damp straw, torches, and resin-based compounds thrown into flames to create smoky, mystical environments for the audience (Shakespeare’s Globe, n.d.). The results were crude and often dangerous, but the artistic impulse was identical to the one driving today’s lighting designers to request “just a little more haze, please.”
In Elizabethan England, companies at the Globe Theatre (1598 to 1613) generated smoke using chemical mixtures including sulphur and saltpetre to simulate magic, fire, and supernatural elements. Shakespeare’s witches in Macbeth refer to “the fog and filthy air,” and the air inside the theatre during those scenes may indeed have been “horrible to breathe in, if not actually dangerous,” as the Globe’s own educational materials acknowledge (Shakespeare’s Globe, n.d.). On June 29, 1613, a cannon fired during a performance of Henry VIII ignited the Globe’s thatch roof and burned the entire theatre to the ground. The history of atmospheric effects and safety failures are intertwined from the very beginning.
The modern era of theatrical fog began in earnest in the 1930s, when Adelaide Hall’s 1934 performance at Harlem’s Cotton Club featured nitrogen-cooled fog covering the stage floor during her rendition of “Ill Wind.” It was reportedly the first use of low-lying fog on a theatrical stage and caused a sensation (Wikipedia, n.d.). For the next several decades, atmospheric effects relied primarily on dry ice, cryogenic gases, and increasingly on petroleum-based thermal foggers originally designed for pesticide distribution.
The 1970s brought the electric fog machine, which vaporizes glycol- or glycerin-based fluids through a resistance heating element to produce a thick, controllable cloud. This technology revolutionized stagecraft because it was reliable, repeatable, relatively portable, and produced effects that could be tuned from a dense ground-hugging cloud to a barely perceptible atmospheric haze (Rosco, 2023). By the 1980s and 1990s, glycol-based fog machines and mineral-oil-based haze machines had become standard equipment in Broadway theatres, regional companies, touring productions, concert venues, film sets, and theme parks worldwide.
The proliferation of these machines created an occupational health question that nobody was asking with sufficient rigor: what happens when performers breathe aerosolized glycol and mineral oil for hours at a time, night after night, for months or years?
NIOSH conducts initial Health Hazard Evaluation (HETA 90-355) at the request of Actors’ Equity Association, examining fog and smoke effects on Broadway. The final report (1994) concludes theatrical fogs may contribute to upper respiratory tract problems including sneezing, nasal congestion, coughs, and sore throat (Burr et al., 1994).
Dr. Jacqueline Moline of Mount Sinai reviews medical records of over 1,200 Equity performers. Data shows that performers in fog-heavy shows were diagnosed with respiratory problems four to five times more frequently than performers in non-fog shows (Rossol, 2021).
The Equity-League Pension and Health Trust Funds commissions a comprehensive study led by Dr. Moline at Mount Sinai School of Medicine, with air monitoring conducted by ENVIRON International Corporation.
The Mount Sinai/ENVIRON study, “Health Effects Evaluation of Theatrical Smoke, Haze, and Pyrotechnics,” is released on June 6. It establishes the peak exposure guidance levels that remain the foundation of all U.S. theatrical fog regulation today (Moline & Golden, 2000).
Actors’ Equity and the League of American Theatres and Producers adopt the Mount Sinai exposure limits for Broadway and touring productions. ENVIRON develops the first Equipment-Based Guidelines (T&D charts) and Air Sampling Protocol (ENVIRON International Corporation, 2001).
ANSI E1.5-2003 is published by ESTA’s Fog and Smoke Working Group, establishing a national consensus standard for theatrical fog composition and exposure limits. The University of British Columbia simultaneously conducts its independent study of entertainment industry workers in Canada (Teschke et al., 2005).
Varughese et al. publish “Effects of Theatrical Smokes and Fogs on Respiratory Health in the Entertainment Industry” in the American Journal of Industrial Medicine, providing independent confirmation of the Mount Sinai findings across a broader population and production types.
ANSI E1.5 is revised and republished. ANSI E1.23-2010 (Design and Execution of Theatrical Fog Effects) is developed to provide comprehensive planning guidance.
ANSI E1.23 is revised to its current edition, adding guidance on maintaining atmospheric effects over months or years in long-running shows and extended film shoots (ESTA, 2020).
Actors’ Equity publishes revised Time & Distance Guidelines (April 7), updated Calibration Factors memo (April 15), and overhauled Smoke and Haze Regulations page and FAQ. ANSI E1.5-2009 is reaffirmed as R2024. These represent the most significant regulatory updates since 2001 (Actors’ Equity Association, 2024a; Ramboll, 2024; USITT, 2024).
That timeline spans 34 years. For most of that period, the regulatory framework remained relatively static after the initial 2000-2001 implementation. The 2024 updates are significant precisely because they represent the first major operational revision in over two decades, and they arrived alongside the discontinuation of the primary monitoring instrument that the entire system was built around.
Understanding Atmospheric Effects: Types, Chemistry, and Mechanics
Before we examine the health science and the regulatory framework, it helps to understand what we are actually putting into the air when we use atmospheric effects. The terminology in our industry is imprecise, and that imprecision contributes to safety misunderstandings. There are four fundamentally different categories of atmospheric effects used in entertainment, and each carries a distinct risk profile (ESTA, 2020; Rossol, 2021).
Fog
Fog is the traditional “make a cloud” effect. It is produced by pumping a glycol-water or glycerin-water solution into a heat exchanger, where the fluid is vaporized at temperatures that may exceed 300 degrees Celsius. The resulting vapor condenses upon contact with cooler ambient air, forming a thick, translucent or opaque cloud of liquid droplets suspended in the atmosphere. Fog is dense, visible, and dramatic. It is also transient; the droplets are relatively large and settle out of the air over time through a combination of gravity and evaporation (ESTA, 2020).
The chemicals used in theatrical fog fluids are primarily dihydric and trihydric alcohols, specifically propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, butylene glycol, and glycerin (glycerol). ANSI E1.5 specifies the eight acceptable alcohol compounds for theatrical fog fluid, all of which must be mixed with deionized water (Entertainment Services and Technology Association, 2024). The health concern with fog is that performers and crew inhale aerosolized glycol or glycerin droplets, which can cause respiratory tract irritation, dry cough, dry throat, headache, dizziness, and fatigue, with symptom severity increasing with concentration and duration of exposure (Moline & Golden, 2000).
A critical safety consideration with heat-based fog generation is the potential for thermal degradation. When fog fluids are overheated beyond their designed operating range, the glycol compounds can decompose into byproducts including formaldehyde, acrolein, and acetaldehyde. All three are known respiratory irritants and potential carcinogens. ANSI E1.5 requires that these decomposition products remain below the permissible exposure limits established by governing occupational health authorities such as OSHA (Entertainment Services and Technology Association, 2024). This is why machine maintenance, proper fluid selection, and manufacturer-specified operating temperatures are not optional; they are fundamental safety controls.
Haze
Haze is a homogeneous, barely visible dispersion of fine particles designed to reveal light beams without creating a distinct “cloud” effect. The audience should see the beams, not the haze itself. Haze can be generated in two fundamentally different ways, and the distinction matters enormously for health and regulatory purposes.
Mineral-oil-based haze machines atomize highly refined mineral oil using either a mechanical spray pump powered by electricity or compressed CO2, or a heat-based cracker system. The resulting aerosol is extremely fine, typically 1 to 10 microns in diameter for ultrasonic/atomizer systems and somewhat larger for heat-based systems (Teschke et al., 2005). Mineral oil haze hangs in the air for extended periods, produces excellent beam visibility, and leaves an oily residue on surfaces.
Glycol-based haze, often marketed as “water-based haze,” uses the same glycol-water chemistry as fog machines but produces a finer, more dispersed output. The health considerations overlap substantially with glycol fog.
The health concern with mineral oil haze is distinct from and in some respects more serious than that of glycol fog. Chronic inhalation of mineral oil aerosol can predispose individuals to lipoid pneumonia, a condition in which oil accumulates in the lungs and triggers an inflammatory response. Once deposited in the lungs, mineral oil is metabolically inert; it does not dissolve or break down and can remain in the tissue indefinitely (Rossol, 2021). This is why the peak exposure limit for mineral oil (25 mg/m3) is significantly lower than the limit for glycol (40 mg/m3), and why the 8-hour time-weighted average for mineral oil is set at just 5 mg/m3 (Moline & Golden, 2000; J&M Special Effects, n.d.).
Smoke
True smoke is a particulate product of combustion. In theatrical applications, smoke is generated by pyrotechnic smoke cookies, smoke cartridges, incense, or HVAC smoke pencils. Unlike fog and haze, which are liquid droplets, smoke consists of solid particles. Smoke is used less frequently in modern entertainment due to the inherent fire risk, greater cleanup requirements, and more limited effect possibilities (ESTA, 2020). The primary hazard is thermal injury from the pyrotechnic itself, followed by respiratory irritation from the combustion particulates. Fire extinguishers must always be immediately accessible when pyrotechnic smoke effects are in use.
Low-Lying Effects (Cryogenic)
Low-lying fog is produced by chilling theatrical fog with liquid carbon dioxide (CO2) or liquid nitrogen, causing the cooled fog to remain within a few feet of the ground. As the fog warms, it rises and dissipates. Dry ice (solid CO2) immersed in heated water produces a similar effect. These cryogenic effects produce a visually stunning rolling ground fog, but they introduce a completely separate set of hazards: frostbite and cryogenic burns from direct contact with the cryogens, and asphyxiation risk from oxygen displacement in enclosed or low-lying spaces. Carbon dioxide is denser than air and accumulates near the floor, potentially causing unconsciousness without warning because the gas is odorless. Liquid nitrogen expands at a ratio of approximately 696 to 1 when it vaporizes, which can rapidly displace breathable air in confined spaces (Wikipedia, n.d.).
Dry ice, liquid CO2, liquid nitrogen, and vaporized water are not listed in the Equity-approved T&D charts because they were not part of the original glycol and mineral oil study. Productions using these substances must contact their Equity Field Representative directly (Actors’ Equity Association, 2024a).
Key Distinction: The Equity regulatory framework and the Mount Sinai study deal primarily with glycol-based fog, glycerol-based fog, and mineral-oil-based haze. These are the three substance categories for which quantifiable peak exposure limits exist. Cryogenic effects, pyrotechnic smoke, and “other substances” fall outside the T&D chart system and require separate coordination with Equity.
The Chemistry of Fog Fluids: A Technical Deep Dive
To understand the health effects and regulatory limits for theatrical fog, you need to understand the chemistry. Most lighting designers, stage managers, and production managers have never been asked to think about fog at the molecular level, but the regulatory framework is built on chemical distinctions that determine which exposure limit applies, what calibration factor to use, and which health effects are relevant. This section provides that foundation.
The Glycol Family: Dihydric Alcohols
Glycols are organic compounds that contain two hydroxyl (OH) groups, which classifies them as dihydric alcohols or diols. The hydroxyl groups make glycols hygroscopic, meaning they readily absorb moisture from their surroundings. This hygroscopic property is precisely why glycols produce visible fog: when aerosolized glycol droplets encounter the water vapor in ambient air, they absorb that moisture and grow into larger droplets that scatter light and become visible. It is also why performers often report dry throat and dry eyes when working in glycol fog. The glycol droplets are literally pulling moisture out of the mucous membranes they contact (Big Clive, n.d.).
Six glycol compounds are approved for use in theatrical fog under ANSI E1.5 and the Equity regulatory framework. Three glycols are specifically prohibited. Understanding the distinction is a matter of performer safety.
Approved Glycols
| Compound | Key Properties | Common Use in Fog Fluids |
| Triethylene Glycol (TEG) | Colorless, nearly odorless, viscous liquid; hygroscopic; low toxicity; excellent light refraction; long aerosol hang time | Primary active ingredient in most professional fog fluids. Preferred for beam-visibility effects due to superior light-scattering properties. EPA has determined no risk concerns for human exposure (Roger George Special Effects, n.d.). |
| Propylene Glycol (PG) | Viscous, colorless, faintly sweet; classified as GRAS (Generally Recognized as Safe) by FDA for oral ingestion; shorter aerosol hang time than TEG | Common in consumer-grade fog fluids and e-cigarette formulations. Produces a thick, dense fog that dissipates more quickly than TEG-based products. Often used in combination with TEG for tuned effects. |
| Dipropylene Glycol (DPG) | Low toxicity; hygroscopic; miscible with water; good solvent properties | Used in professional fog fluids, often blended with TEG or PG. Common in perfume and skin care applications, confirming its low dermal toxicity profile. |
| Polyethylene Glycol (PEG) | Variable molecular weight; water-soluble; low toxicity; used extensively in pharmaceuticals | Less common in fog fluids but occasionally used in specialty formulations. Widely used in pharmaceutical and cosmetic applications. |
| 1,2-Butylene Glycol | Low volatility; hygroscopic; used in cosmetics and food applications | Specialty fog fluid component. Less commonly encountered in standard theatrical products. |
| 1,3-Butylene Glycol | Colorless, viscous; good solvent; low dermal irritation potential | Specialty fog fluid component. More commonly found in Asian-manufactured products. |
Prohibited Glycols
| Compound | Why Prohibited |
| Ethylene Glycol | Toxic when ingested. Metabolized to oxalic acid, which causes renal failure. This is the primary ingredient in automotive antifreeze and has caused hundreds of poisoning deaths worldwide. Although inhalation toxicity at theatrical concentrations is low, the risk of confusion with propylene glycol and the compound’s well-documented systemic toxicity make it unacceptable for theatrical use (American Chemistry Council, n.d.). |
| Diethylene Glycol (DEG) | Documented history of mass poisoning events when substituted for propylene glycol in pharmaceutical products. Responsible for the 1937 Elixir Sulfanilamide disaster (105 deaths), poisoning incidents in Nigeria, Bangladesh, Panama, and China, and the 2022 pediatric deaths in Indonesia and The Gambia. DEG can be a normal ingredient in fog fluid at low concentrations but is prohibited as a primary active ingredient (Wikipedia, n.d.). |
| 1,4-Butylene Glycol | Higher toxicity profile than approved butylene glycol isomers. Not suitable for aerosolization and inhalation. |
Critical Safety Note: The distinction between approved and prohibited glycols is not academic. The chemical names are similar, and fluid labeling is not always clear about which specific glycol compounds are present. Never use a fog fluid without first obtaining and reviewing its Safety Data Sheet (SDS). If specific ingredients are not listed on the SDS, do not use the product. Contact the manufacturer to verify the exact chemical composition before introducing any fluid into your production (Washington State Department of Health, 2023).
Glycerol (Glycerin): The Trihydric Alcohol
Glycerol is chemically distinct from glycols. Where glycols have two hydroxyl groups, glycerol has three, making it a trihydric alcohol. Glycerol is the active ingredient in glycerin-based fog fluids and produces a particularly dense, long-lasting fog with a slightly different visual quality than glycol fog. Glycerol fog tends to leave a noticeable residue on surfaces, which is why pure glycerin formulations have become less common in professional theatrical use, though they remain popular in specialty applications like the Rosco Radiance system (Big Clive, n.d.).
The health concern with glycerol fog is primarily respiratory irritation at elevated concentrations, with a peak exposure guidance level of 50 mg/m3. Glycerol has a higher peak limit than glycol (40 mg/m3) because its larger molecular weight and different hygroscopic profile produce somewhat less respiratory irritation per unit of mass concentration. However, glycerol carries a unique thermal degradation risk: when overheated above its designed vaporization temperature, glycerol can decompose into acrolein, a highly reactive aldehyde that is a potent respiratory irritant and lachrymator (tear-inducing agent). This is why glycerol-based fog machines must have precisely regulated heating elements calibrated specifically for glycerin fluids. A standard glycol-rated fog machine should not be used with glycerin fluid, and vice versa, because the different thermal degradation thresholds mean overheating one type of fluid in a machine designed for the other can produce dangerous decomposition products (Big Clive, n.d.; Look Solutions USA, 2022).
Mineral Oil: The Alkane Haze Medium
Mineral oil used in theatrical haze machines is a highly refined alkane hydrocarbon derived from petroleum. The refining process is critical: only highly refined, food-grade or pharmaceutical-grade mineral oils are acceptable for theatrical use. Crude or mildly refined mineral oils contain polycyclic aromatic hydrocarbons (PAHs) and other impurities that are known carcinogens and respiratory toxins (Teschke et al., 2005). The ACGIH distinguishes between mildly refined and highly refined mineral oil mists in its exposure guidelines, with the TLV for mildly refined oils set at 0.2 mg/m3 as inhalable aerosol, while the TLV for severely refined mineral oil mist was historically set at 5 mg/m3 (Actsafe Safety Association, 2003).
Even highly refined mineral oil presents a distinct and more serious respiratory risk than glycol or glycerol. When inhaled, mineral oil droplets deposit in the alveolar spaces of the lungs. Unlike glycol droplets, which are water-miscible and can be absorbed and metabolized by the body, mineral oil is biologically inert. It does not dissolve in biological fluids, and the body cannot metabolize it. Once deposited in the lungs, mineral oil remains in the tissue indefinitely, triggering a chronic foreign body reaction characterized by the accumulation of lipid-laden macrophages (Rossol, 2021).
This process, if exposure is sufficient in dose and duration, can lead to exogenous lipoid pneumonia, a rare but well-documented occupational lung disease. Lipoid pneumonia was first defined in 1925 and is characterized by fat-containing products accumulating in the distal airways and alveoli, producing an inflammatory reaction that impairs gas exchange (StatPearls, 2023). The condition is insidious: mineral oil inhalation does not induce an obvious reactive response in the airways, so the exposure may go unnoticed. Chronic lipoid pneumonia presents with diverse and non-specific clinical and radiological characteristics that can mimic lung tumors, pulmonary tuberculosis, and fibrosis, making it readily misdiagnosed (Jia et al., 2016).
The relevance to theatrical haze is direct. Mineral-oil-based haze machines are among the most commonly used atmospheric effects devices in the entertainment industry because mineral oil haze produces excellent beam visibility, hangs in the air for extended periods, and is nearly invisible to the audience. However, this persistence is precisely what makes it a respiratory concern: mineral oil aerosol stays in the air longer than glycol fog, accumulates to higher ambient concentrations with continuous use, and deposits in the lungs with greater efficiency because the fine particles (typically 1 to 10 microns) penetrate deeply into the respiratory tract (Teschke et al., 2005).
This is why the peak exposure guidance level for mineral oil (25 mg/m3) is the most restrictive of the three substance categories, and why the 8-hour time-weighted average (5 mg/m3) is half the TWA for glycol and glycerol. The Canadian workers’ compensation framework is even more restrictive, with an 8-hour exposure limit of just 0.2 mg/m3 for mildly refined oils (Actsafe Safety Association, 2003).
Thermal Degradation Products: The Hidden Hazard
The most dangerous chemical exposures from theatrical fog are not the fog chemicals themselves but the products of their thermal decomposition when improperly heated. When glycol, glycerol, or mineral oil compounds are heated beyond their designed vaporization temperature, they can break down into a range of toxic byproducts.
The primary decomposition products of concern are formaldehyde (HCHO), acrolein (CH2=CHCHO), and acetaldehyde (CH3CHO). All three are classified as respiratory irritants. Formaldehyde is also classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). Acrolein is one of the most potent respiratory irritants known, with an immediately dangerous to life or health (IDLH) concentration of just 2 ppm (NIOSH). Acetaldehyde is a probable human carcinogen (IARC Group 2B).
ANSI E1.5 requires that thermal degradation products remain below OSHA permissible exposure limits, and fog machine manufacturers are required to design their heating systems to vaporize the specified fluid without exceeding the thermal decomposition threshold (Entertainment Services and Technology Association, 2024). This is why using manufacturer-specified fluids in manufacturer-specified machines at manufacturer-specified operating conditions is not merely a warranty issue; it is a health and safety imperative. A machine designed to vaporize triethylene glycol at a specific temperature will produce safe aerosol at that temperature. The same machine operating at a higher temperature, or operating with a different fluid that has a lower decomposition threshold, may produce formaldehyde or acrolein at concentrations that pose a genuine health risk.
A 2022 study published in PubMed investigated the impact of glycol-based aerosol on indoor air quality, measuring time-resolved aerosol profiles and chemical compositions of fog generated from propylene glycol and triethylene glycol. The researchers found that artificial fog produced significant amounts of ultra-fine particulate matter and confirmed that thermal degradation can generate carbonyl compounds at measurable concentrations, reinforcing the importance of proper machine maintenance and temperature control (PubMed, 2022).
Aerosol Science: Understanding Particle Behavior
The health effects of any inhaled substance depend not just on what the substance is, but on the size of the particles carrying it into the respiratory tract. This is a fundamental principle of industrial hygiene that has direct practical implications for theatrical fog and haze management.
Aerosol particles are classified by their aerodynamic diameter, which determines how deeply they penetrate into the lungs. Particles larger than approximately 10 microns are filtered by the nose and throat and do not reach the lower airways. Particles between 3.5 and 10 microns deposit in the upper bronchial airways. Particles smaller than 3.5 microns can reach the terminal bronchioles and alveolar air sacs, where gas exchange occurs and where the potential for respiratory damage is greatest.
The British Columbia exposure study found that the mean proportion of theatrical fog aerosol mass with an aerodynamic diameter less than 3.5 microns was 61 percent (Teschke et al., 2005). This means that the majority of the fog mass in a typical theatrical production is in the respirable fraction, capable of reaching the deepest parts of the lungs. This finding is significant because it means that theatrical fog is not merely an upper-airway irritant; it is delivering active chemical compounds to the most sensitive and least protected regions of the respiratory system.
Different fog and haze generation methods produce different particle size distributions. Heat-based fog machines (glycol and glycerol) produce aerosols across a wide size range, with the median particle size depending on the fluid composition, heating temperature, and output nozzle design. Mechanical atomizer (“cracker”) haze machines produce particles in the 10 to 20 micron range. Ultrasonic haze machines produce the finest aerosols, typically 1 to 10 microns, with a higher proportion of the output in the deeply respirable fraction (Actsafe Safety Association, 2003).
From a health perspective, this means that not all fog machines with the same output volume present the same respiratory risk. A machine that produces larger particles (which settle faster and deposit in the upper airways) is inherently less concerning than a machine that produces very fine particles (which hang in the air longer and penetrate deeper into the lungs). The T&D charts account for this indirectly, because the testing was done on specific machine-fluid combinations that each produce a characteristic particle size distribution. Substituting a different machine changes the particle size distribution and invalidates the T&D data.
Particle behavior in enclosed spaces is also influenced by air circulation, temperature, and humidity. Warmer air holds more moisture and can keep hygroscopic glycol droplets suspended longer. HVAC systems that recirculate indoor air redistribute aerosol particles throughout the space rather than exhausting them. High humidity reduces the hygroscopic growth of glycol droplets (because the air already contains the moisture the droplets would otherwise absorb), potentially keeping particles smaller and more deeply respirable for longer (Teschke et al., 2005).
The Health Science: What the Research Actually Says
The health effects of theatrical fog and haze have been studied more rigorously than most people in our industry realize. The body of evidence is not ambiguous. It consistently demonstrates that exposure to aerosolized glycol and mineral oil causes measurable, dose-dependent respiratory effects in entertainment industry workers. The question has never been whether these substances cause harm at elevated concentrations. The question has always been: at what concentration does the harm become clinically significant, and how do we keep performers below that threshold?
Three major studies form the evidentiary foundation of current regulation.
The NIOSH Health Hazard Evaluation (1990-1994)
The earliest formal investigation began when Actors’ Equity Association requested a Health Hazard Evaluation (HETA 90-355) from the National Institute for Occupational Safety and Health in 1990. The final report, released in August 1994, concluded that theatrical fogs may contribute to upper respiratory tract problems among Broadway performers and crew, including sneezing, nasal congestion, coughs, breathlessness, and sore or dry throat (Burr et al., 1994). The NIOSH evaluation was important as a signal that a problem existed, but its methodology was limited, and it did not produce the quantified exposure limits that the industry needed for operational regulation.
Dr. Moline’s Medical Records Analysis (1995-1996)
In 1995, Dr. Jacqueline Moline of the Mount Sinai-Irving J. Selikoff Center for Environmental and Occupational Medicine examined the medical records of over 1,200 Equity performers. The analysis revealed that performers working in fog-heavy shows were diagnosed and treated for respiratory problems four to five times more frequently than performers in non-fog shows (Rossol, 2021). Separately, Dr. Moline conducted direct medical examinations of 25 pit musicians at Beauty and the Beast, where she found clear evidence of symptomatic respiratory distress. Her assessment was blunt: “The conditions for the musicians in the music pit at Beauty and the Beast are unhealthy. A large percentage of the musicians are suffering from symptoms related to the irritative effects of the work environment” (Rossol, 2021).
These preliminary findings provided the justification for the comprehensive study that followed.
The Mount Sinai/ENVIRON Study: The Foundation of Everything
In 1997, the Trustees of the Equity-League Pension and Health Trust Funds commissioned the study that would become the single most important document in the regulation of theatrical atmospheric effects in the United States. Led by Dr. Jacqueline Moline at the Mount Sinai School of Medicine, with air monitoring and environmental analysis conducted by ENVIRON International Corporation, the study was titled “Health Effects Evaluation of Theatrical Smoke, Haze, and Pyrotechnics” and was released on June 6, 2000 (Moline & Golden, 2000).
The study evaluated Broadway performers through a combination of questionnaires, medical monitoring, personal air sampling, and area air sampling across multiple productions. The findings were significant and unambiguous in their core conclusions.
“The results of the Mt. Sinai/ENVIRON study indicate that there are certain health effects associated with actors exposed to elevated or peak levels of glycol smoke and mineral oil. However, as long as peak exposures are avoided, actors’ health, vocal abilities, and careers should not be harmed.”
— ENVIRON International Corporation, Equipment-Based Guidelines, 2001
Specifically, the study found that increased respiratory and mucous-membrane symptoms, including dry cough, dry throat, headache, dizziness, and tiredness, were significantly associated with exposure to glycol-based fogs. A measurable drop in lung function was more commonly observed when mineral oil fogs were used (Backstage, 2003). The symptoms were dose-dependent: higher concentrations and longer exposure durations correlated with more frequent and more severe symptoms.
Based on these findings, Mount Sinai and ENVIRON recommended the following peak exposure guidance levels for theatrical performers:
| Substance | Peak Exposure Limit | 8-Hour TWA | Primary Health Concern |
| Glycol | 40 mg/m³ | 10 mg/m³ (per ANSI E1.5) | Respiratory irritation, dry cough, throat dryness, headache, fatigue |
| Glycerol | 50 mg/m³ | 10 mg/m³ | Respiratory and mucous membrane irritation |
| Mineral Oil | 25 mg/m³ | 5 mg/m³ | Lipoid pneumonia risk, reduced lung function, respiratory irritation |
These guidance levels are not regulatory standards in the OSHA sense. They are health-based recommendations developed by occupational health researchers to protect a specific population (theatrical performers) from a specific exposure (aerosolized fog and haze chemicals in enclosed venues). They have, however, been adopted as binding requirements through Equity’s collective bargaining agreements and referenced as authoritative values by ANSI E1.5 and ANSI E1.23 (Entertainment Services and Technology Association, 2024; ESTA, 2020).
The study also found that pyrotechnics as used on Broadway at the time did not have significant adverse health effects at the levels measured, which is why the regulatory framework focuses primarily on fog and haze rather than pyrotechnic smoke (ENVIRON International Corporation, 2001).
It is worth pausing on the phrase “as long as peak exposures are avoided.” This framing is critical because it establishes the regulatory philosophy that has governed the industry for the past 25 years: the goal is not to ban atmospheric effects, but to ensure that performers are never exposed to concentration peaks above the guidance levels. Every compliance mechanism that follows, from T&D charts to air sampling protocols, is an engineering control designed to achieve that single objective.
The British Columbia Study: Independent Confirmation
The third major piece of evidence arrived in 2005 when Varughese, Teschke, Brauer, Chow, van Netten, and Kennedy published “Effects of Theatrical Smokes and Fogs on Respiratory Health in the Entertainment Industry” in the American Journal of Industrial Medicine. This study was conducted at the University of British Columbia’s School of Occupational and Environmental Hygiene and examined 101 entertainment industry employees across 19 production sites in British Columbia, Canada (Varughese et al., 2005).
The British Columbia study was methodologically important because it went beyond Broadway. The researchers measured personal fog exposures, performed across-work-shift lung function tests, and assessed both acute and chronic symptoms among employees working in a range of production types, including television, film, live theatre, and concerts. Results were compared to an external control population of British Columbia Ferry Corporation employees who had been studied previously.
The findings confirmed and extended the Mount Sinai results across a broader population and production context:
Chronic work-related wheezing and chest tightness were significantly associated with increased cumulative exposure to mineral oil and glycol fogs over the previous two years. Acute cough and dry throat were associated with acute exposure to glycol-based fogs specifically. Increased acute upper airway symptoms were associated with increased fog aerosol overall, regardless of type. Lung function was significantly lower among those working closest to the fog source. Compared to the control group, entertainment industry employees had lower average lung function test results and reported more chronic respiratory symptoms: nasal symptoms, cough, phlegm, wheezing, and chest tightness (Varughese et al., 2005).
A companion exposure study by Teschke et al. (2005), published in the Journal of Occupational and Environmental Hygiene, measured personal inhalable aerosol concentrations across the same production sites and found that the most important factors determining exposure levels were distance from the fog machine, the number of fog machines in use, and the percentage of time spent in visible fog. Exposures were higher when mineral oils were used to generate fogs, higher on movie and television productions (which tend to use fog more continuously), higher when more than one fog machine was in use, and higher for workers employed as “grips” who worked in close proximity to the machines (Teschke et al., 2005).
The researchers also measured the particle size distribution of theatrical fog aerosols and found that the mean proportion of total aerosol mass with an aerodynamic diameter of less than 3.5 microns was 61 percent (Teschke et al., 2005). This is significant because particles below 3.5 microns can penetrate into the smallest airways and air sacs of the lungs, increasing the potential for deep respiratory irritation and long-term damage.
The consistent conclusion across all three studies: Mineral oil and glycol-based fogs are associated with both acute and chronic adverse effects on respiratory health among entertainment industry employees. Reducing exposure through engineering controls, substitution, and elimination where possible is likely to reduce these effects (Varughese et al., 2005).
Lipoid Pneumonia: The Mineral Oil Risk in Detail
Of all the health concerns associated with theatrical atmospheric effects, exogenous lipoid pneumonia from mineral oil inhalation deserves the most detailed examination because it represents the most serious potential long-term consequence of inadequately controlled haze exposure. While most glycol-related symptoms resolve when exposure ceases, lipoid pneumonia can cause persistent and potentially irreversible lung damage.
Lipoid pneumonia was first described in 1925 by Laughlin and is classified into two categories: exogenous (caused by inhaling or aspirating external fat-containing substances) and endogenous (caused by fat released from the body’s own tissues due to airway obstruction or metabolic disorders). The exogenous form is relevant to theatrical haze because it results from the chronic inhalation of aerosolized mineral oil (StatPearls, 2023).
The pathophysiology is straightforward but insidious. When aerosolized mineral oil particles are inhaled into the alveolar spaces, alveolar macrophages (immune cells responsible for clearing foreign material from the lungs) engulf the oil droplets. However, because mineral oil is metabolically inert, the macrophages cannot break it down. The oil-laden macrophages accumulate in the alveoli, triggering a chronic foreign body inflammatory reaction. Over time, this inflammation can produce fibrosis (scarring), consolidation (filling of air spaces with inflammatory material), and impaired gas exchange. On CT imaging, lipoid pneumonia appears as ground-glass opacities, consolidative opacities with areas of low attenuation (fat density), and in advanced cases, a “crazy paving” pattern of ground-glass opacities with superimposed interlobular septal thickening (Betancourt et al., 2010; Gondouin et al., 1996).
The condition is notoriously difficult to diagnose because its symptoms (cough, dyspnea, low-grade fever, weight loss) and imaging findings mimic many other lung diseases, including bacterial pneumonia, tuberculosis, and primary lung cancer. Lipoid pneumonia is frequently misdiagnosed or missed entirely, and autopsy series suggest the true incidence may be 1 to 2.5 percent of the population (StatPearls, 2023). Diagnosis typically requires bronchoalveolar lavage (BAL) or lung biopsy demonstrating lipid-laden macrophages, combined with a compatible exposure history.
The critical risk factor is chronic, repeated exposure at concentrations that may not produce noticeable acute symptoms. A performer working in a mineral-oil-hazed venue might not experience obvious throat irritation or coughing, because the acute symptom threshold for mineral oil is different from glycol. The Varughese et al. (2005) study specifically noted that “a measurable drop in lung function was more often seen when mineral oil fogs were used on the testing day,” even when acute subjective symptoms were less prominent than with glycol exposures. This means that the absence of acute symptoms does not indicate the absence of harm with mineral oil haze.
One particularly relevant case in the literature involved nine wild American white ibis that died within 24 hours of exposure to theatrical fog containing propylene glycol and triethylene glycol at a Halloween event at a zoological institution. Gross examinations revealed congestion, edema, and hemorrhage throughout the lungs, with histological changes indicative of acute respiratory insult (ResearchGate, 2005). While this case involved glycol rather than mineral oil, and birds have a fundamentally different respiratory system than humans, it illustrates the potential for acute respiratory damage at high concentrations and reinforces the importance of controlling peak exposures.
For theatrical productions, the practical takeaway is clear: mineral oil haze requires more conservative management than glycol fog. The lower peak exposure limit (25 mg/m3 vs. 40 mg/m3 for glycol) reflects this differential risk. Productions should use the minimum concentration of mineral oil haze necessary to achieve the desired lighting effect, ensure robust ventilation to prevent aerosol accumulation, and consider glycol-based alternatives when the visual requirements can be met with glycol products. For long-running shows using continuous mineral oil haze, periodic lung function testing for regularly exposed personnel is a reasonable precaution, though not currently required by Equity or ANSI.
The E-Cigarette Research Connection
An unexpected source of new data on glycol inhalation health effects has emerged from the extensive body of research on electronic cigarettes (e-cigarettes or vaping devices). E-cigarettes heat a liquid (commonly called “e-liquid” or “vape juice”) containing propylene glycol, vegetable glycerin (glycerol), nicotine, and flavorings to produce an inhalable aerosol. The heating mechanism is functionally identical to a theatrical fog machine: a resistance heating element vaporizes a glycol-water solution, and the resulting vapor condenses into an aerosol upon contact with cooler ambient air.
The explosion of vaping-related research since 2010 has produced thousands of studies on the respiratory effects of inhaled propylene glycol and glycerol aerosols, providing a much larger evidence base than the entertainment industry alone could generate. While the exposure patterns differ (vaping involves direct inhalation of concentrated aerosol from a personal device, whereas theatrical fog involves ambient exposure to more dilute aerosol in a performance space), the underlying chemistry is the same, and the research findings reinforce the conclusions of the Mount Sinai and British Columbia studies.
Key findings from the e-cigarette literature relevant to theatrical fog include: propylene glycol aerosol inhalation is associated with acute respiratory symptoms including cough, throat irritation, and reduced lung function, consistent with the theatrical fog studies; chronic inhalation of propylene glycol and glycerol aerosols can cause airway inflammation and increased susceptibility to respiratory infections; thermal degradation of propylene glycol at elevated temperatures produces formaldehyde and other carbonyls at concentrations that exceed occupational exposure limits; and the respiratory effects are dose-dependent, with higher concentrations and longer exposure durations producing more severe effects (ResearchGate, 2005).
The e-cigarette research has also highlighted a concern that was not fully appreciated in the original theatrical fog studies: the potential for repeated, chronic low-level exposure to produce cumulative effects that are not detectable in acute exposure studies. The Mount Sinai study examined Broadway performers over a limited study period. The British Columbia study assessed chronic symptoms over a two-year retrospective window. Neither study followed a cohort of entertainment industry workers over a period of decades to assess the true long-term cumulative effects of career-length exposure. The e-cigarette literature, while still young, is beginning to suggest that chronic low-level glycol aerosol inhalation may have effects on airway remodeling and immune function that only become apparent after years of exposure.
Vulnerable Populations: Who Is Most at Risk
The health effects data from all three major studies and the broader aerosol science literature consistently identify several populations at elevated risk from theatrical fog and haze exposure.
Individuals with pre-existing respiratory conditions, including asthma, chronic bronchitis, chronic obstructive pulmonary disease (COPD), and reactive airway disease, are significantly more sensitive to fog and haze aerosols than healthy individuals. The exposure concentrations that produce no noticeable symptoms in a healthy performer may trigger bronchospasm, asthma attacks, or significant respiratory distress in an individual with compromised airway function (Aura Health and Safety Corporation, 2018). Equity’s regulations do not differentiate exposure limits based on individual health status, which means that the published guidance levels may not be sufficiently protective for performers with respiratory conditions.
Children, as discussed in detail in the Special Populations section, have smaller airway diameters, higher respiratory rates, and higher ventilation rates per unit of body weight than adults. They receive proportionally larger doses of inhaled aerosol for a given ambient concentration and may not be able to recognize or articulate symptoms of respiratory distress. The ANSI E1.5 exposure limits explicitly apply only to “otherwise healthy performers, technicians, or audience members of normal working age” (18 to 64) and make no statement about appropriate limits for children (Entertainment Services and Technology Association, 2024).
Elderly individuals experience age-related decline in lung function, reduced mucociliary clearance, and increased susceptibility to respiratory infections. They may also have undiagnosed or subclinical respiratory conditions that are exacerbated by aerosol exposure.
Individuals with contact lens wear may experience increased eye irritation from glycol fog because the hygroscopic aerosol interferes with the tear film that lubricates the lens-cornea interface. This is uncomfortable but generally not harmful; however, it can impair visual acuity during performance.
Singers and vocal performers represent a special case because their instrument (the vocal tract) is the anatomical region most directly and immediately affected by fog and haze exposure. The hygroscopic properties of glycol fog dry the mucosal surfaces of the pharynx and larynx, altering vocal fold lubrication and potentially affecting vocal quality, range, and endurance. Dr. Moline’s assessment of the Beauty and the Beast pit musicians specifically noted that the work environment was “unhealthy” and that musicians were suffering from “symptoms related to the irritative effects of the work environment” (Rossol, 2021). The National Association of Teachers of Singing (NATS) published Rossol’s comprehensive review article on theatrical fog in the Journal of Singing in 2021, reflecting the vocal performance community’s concern about atmospheric effects and their impact on vocal health.
Comparative Exposure Limit Analysis
Understanding where the Equity/ANSI exposure limits fall in comparison to other regulatory frameworks provides useful context for evaluating their conservatism.
| Authority | Substance | Limit Type | Value |
| Equity/Mount Sinai | Glycol (general) | Peak | 40 mg/m³ |
| OSHA (1989, vacated) | Ethylene glycol | PEL (ceiling) | 127 mg/m³ (50 ppm) |
| ACGIH | Propylene glycol | TLV (not established) | No specific TLV published |
| Equity/Mount Sinai | Mineral oil | Peak | 25 mg/m³ |
| ACGIH | Mineral oil (highly refined) | TLV-TWA | 5 mg/m³ |
| BC WCB (Canada) | Mineral oil (mildly refined) | 8-Hour EL | 0.2 mg/m³ |
| BC WCB (Canada) | Mineral oil (severely refined) | 8-Hour EL | 1 mg/m³ |
| Equity/Mount Sinai | Glycerol | Peak | 50 mg/m³ |
| ACGIH | Glycerol mist | TLV-TWA | 10 mg/m³ |
Several observations are worth noting. The OSHA PEL for ethylene glycol (127 mg/m3) is over three times the Equity peak limit for glycol fog (40 mg/m3), but the OSHA standard was developed for industrial settings where ethylene glycol vapor exposure occurs during manufacturing, not for theatrical settings where aerosolized glycol droplets are inhaled at breathing height. The aerosol form is more concerning than vapor because the liquid droplets deliver a higher dose of the active compound to the airway surfaces. Furthermore, the OSHA PEL was vacated by a federal court in 1992 and has not been readopted, though OSHA considers it indicative of the agency’s position (American Chemistry Council, n.d.).
The Canadian exposure limits for mineral oil, particularly the 0.2 mg/m3 8-hour limit for mildly refined oils, are dramatically more restrictive than the Equity peak limit of 25 mg/m3. While this comparison is not directly equivalent (the Canadian limit applies to TWA over an 8-hour shift, not a peak exposure during a specific cue), it suggests that the U.S. theatrical framework may be less conservative than some international jurisdictions for mineral oil specifically.
The Regulatory Framework: Who Makes the Rules
One of the most confusing aspects of theatrical fog safety is the overlapping and sometimes contradictory regulatory landscape. There is no single authority that governs all atmospheric effects in all entertainment contexts. Instead, the regulatory framework is a patchwork of union agreements, voluntary consensus standards, federal workplace safety law, and state or local regulations. Understanding who makes which rules, and where they apply, is essential for compliance.
Actors’ Equity Association (AEA)
Equity’s smoke and haze regulations apply to all productions operating under an Equity contract. This includes Broadway, national tours, LORT regional theatres, Off-Broadway, stock/dinner theatre, and numerous other production types. Equity’s requirements are contractual obligations, not voluntary guidelines. They are enforceable through grievance procedures, and non-compliance can result in contract violations, fines, and work stoppages. The regulations are grounded in the Mount Sinai study and administered through the Safe and Sanitary provisions of each applicable rulebook (Actors’ Equity Association, 2024a).
Equity requires that producers use only products tested as part of the Mount Sinai study or substances specifically excluded from the study’s scope (dry ice, liquid CO2, liquid nitrogen, vaporized water). Producers must use exact machine, fluid, and attachment combinations as specified in the T&D charts, or conduct air sampling. All productions using atmospheric effects must notify Equity in writing and submit a contract-specific smoke and haze report no later than technical rehearsals. If cues or products change after the report is filed, the report must be updated (Actors’ Equity Association, 2024a).
Entertainment Services and Technology Association (ESTA) / Technical Standards Program (TSP)
ESTA maintains the ANSI-accredited Technical Standards Program, which produces the nationally recognized consensus standards for the entertainment industry. The relevant fog and haze standards are developed by the Fog and Smoke Working Group, a volunteer body of industry professionals, and undergo ANSI-accredited public review and comment processes before adoption (ESTA, n.d.).
Equity explicitly references ANSI standards as applicable where Equity agreements do not define a specific requirement. The Equity Technical Standards page states: “If there is a particular production element planned for a show that is not defined in Actors’ Equity agreements, the ANSI standards shall be in effect” (Actors’ Equity Association, n.d.).
OSHA and State Occupational Safety Agencies
The Occupational Safety and Health Administration establishes permissible exposure limits (PELs) for workplace chemicals, including some components of fog and haze fluids. However, OSHA’s PELs for glycols and mineral oil were developed for industrial manufacturing contexts, not for theatrical applications where the aerosol composition, particle size distribution, and exposure patterns differ significantly from factory environments (Teschke et al., 2005). The Equity and ANSI limits are generally more protective than OSHA’s PELs for these specific substances in a theatrical context, which is why the industry has adopted the study-based guidance levels rather than relying on federal workplace standards.
State and Local Regulations
Several states have developed their own guidance for theatrical fog use, particularly in educational settings. Washington State’s Department of Health published guidelines in 2023 specifically addressing K-12 school theatrical productions, referencing both the Equity framework and ANSI E1.23 (Washington State Department of Health, 2023). Other states may have fire code provisions, indoor air quality regulations, or school safety requirements that interact with atmospheric effects usage.
ANSI E1.5, E1.23, and E1.29: The National Standards
Three ANSI standards published through ESTA’s Technical Standards Program form the national consensus framework for theatrical atmospheric effects. Understanding their scope and relationship to each other is essential for anyone designing, executing, or managing fog and haze effects.
ANSI E1.5-2009 (R2024): Theatrical Fog Composition and Exposure Limits
ANSI E1.5 is the foundational composition and exposure standard. It describes the acceptable chemical composition of theatrical fogs or artificial mists made from aqueous solutions of dihydric and trihydric alcohols (glycols and glycerin). The standard specifies what can be in the fog fluid, how much can be in the air, and the exposure limits below which the fog is judged “not likely to be harmful to otherwise healthy performers, technicians, or audience members of normal working age” (Entertainment Services and Technology Association, 2024).
The key exposure limits established by E1.5 are:
| Parameter | Limit |
| Total glycol concentration, time-weighted average (TWA) | 10 mg/m³ |
| Glycol (dihydric alcohol) short-term exposure limit (STEL) | 40 mg/m³ |
| Glycerol (trihydric alcohol) ceiling | 50 mg/m³ |
| Thermal degradation products (formaldehyde, acrolein, etc.) | Below OSHA PELs |
The standard was originally published in 2003, revised in 2009, and has been reaffirmed at regular intervals. The most recent reaffirmation, R2024, was announced alongside several other ESTA standards reaffirmations and confirms that the technical content remains current and applicable (USITT, 2024). E1.5 is limited to glycol and glycerin fogs; it does not address mineral oil haze, cryogenic effects, or pyrotechnic smoke.
ANSI E1.23-2020: Design, Execution, and Maintenance of Atmospheric Effects
ANSI E1.23 is the comprehensive planning and operational standard. It offers guidance on designing, executing, and maintaining theatrical effects using glycol, glycerin, or white mineral oil fogs or mists in theatres, arenas, motion picture studios, and other places of public assembly (ESTA, 2020). Where E1.5 tells you what can be in the fog, E1.23 tells you how to plan and operate fog effects safely and consistently.
The 2020 edition is particularly notable for adding guidance on developing strategies to maintain an atmospheric effect over the months or years of a long-running show or an extended film shoot. This addresses a practical reality that the original standards did not fully contemplate: fog machines age, fluid lots vary, ventilation systems change, and seasonal climate shifts affect how effects behave in a given space. E1.23 provides the framework for monitoring and adjusting over time (ESTA, 2020; ANSI Blog, 2020).
E1.23 is applicable to all twelve liquid substances commonly used to create theatrical fogs and mists, giving it broader scope than E1.5. Its primary interests include preventing harm to people and equipment, ensuring effects are not toxic or harmful from direct contact, avoiding the creation of fire or egress hazards, preventing false fire alarms, and ensuring that effects are executed as designed, performance after performance (ANSI Blog, 2020).
ANSI E1.29-2009 (R2018): Product Safety Standard for Fog Generators
ANSI E1.29 addresses the safety of the fog machine hardware itself. While fog generators are often evaluated as heating appliances for fire and shock hazards, E1.29 also includes safety tests for the fog generated, bridging the gap between equipment safety and output safety (USITT, 2024). Additional ESTA standards relevant to atmospheric effects include E1.14-2018 (recommendations for fog equipment manuals) and E1.40-2016 (recommendations for theatrical dust effects).
The Relationship Between Equity and ANSI: Equity’s regulations are contractual requirements that apply to Equity productions. ANSI standards are voluntary consensus standards that apply across the entire entertainment industry. Where both apply, the more restrictive requirement governs. In practice, the Equity T&D charts and calibration factors are more operationally specific than ANSI E1.5’s exposure limits, while ANSI E1.23 provides planning and execution guidance that Equity does not replicate. A well-run production should reference both frameworks.
The 2024 Equity Overhaul: Three Major Updates
With the historical, scientific, and regulatory context established, we can now examine the specific changes that Equity implemented in 2024. There are three major updates, and each addresses a different dimension of the compliance framework.
Revised Time and Distance Guidelines. Ramboll (formerly ENVIRON) developed updated T&D tables approved by both Actors’ Equity and the Broadway League. The revised tables, dated April 7, 2024, include testing data for newer machine and fluid combinations that did not exist when the original charts were published. They specify the minimum wait time and minimum distance from the discharge point for each tested machine, fluid, and attachment combination at specified cue lengths (Ramboll, 2024). The T&D Guidelines were developed under conservative use assumptions, including no on-stage activities or props that would enhance dispersion, and cue release at breathing height level. These assumptions mean that actual concentrations on many stages will fall below the guidance levels before the times specified in the charts, which is by design (ENVIRON International Corporation, 2001).
Updated Calibration Factors. Equity released a revised Calibration Factors technical memo dated April 15, 2024 (Actors’ Equity Association, 2024b). Calibration factors are mathematical correction values that account for the difference between what a portable aerosol monitor reads (optical particle count) and the actual mass concentration of a specific fog or haze product in the air. Every fog fluid produces aerosol particles of different sizes and optical properties, which means a given monitor reading corresponds to different actual mass concentrations depending on which product is being sampled. Without the correct calibration factor, raw monitor data cannot be meaningfully compared to the peak exposure guidance levels. The updated memo includes calibration factors for newer products and clarifies the calculation methodology for productions using multiple products simultaneously.
Clarified Compliance Expectations and Reporting Requirements. Equity’s Smoke and Haze Regulations page and FAQ were overhauled and republished in 2024 to eliminate ambiguity on several points that had caused confusion in the field (Actors’ Equity Association, 2024a; Actors’ Equity Association, 2024c). The most consequential clarifications include: all fog and haze products are treated as combinations of water plus glycol, mineral oil, or glycerol, regardless of how they are marketed; products labeled “water-based” are not exempt from reporting or exposure-limit requirements; producers cannot mix and match machines, fluids, and attachments outside the specific combinations listed in the T&D charts; air sampling must begin the first day effects are introduced to the stage, in no event later than technical rehearsals; and data results must be submitted to Equity at safety@actorsequity.org once levels are confirmed below the limits.
Time and Distance Guidelines: A Deep Dive
The T&D charts are the primary compliance tool for most Equity productions, and understanding how they work at a granular level is essential for anyone designing or staging atmospheric effects.
Each row in the T&D table represents a single tested combination of three elements: a specific fog or haze machine, a specific fluid, and a specific attachment or output configuration. The combination is not interchangeable. You cannot use a fluid tested in one machine with a different machine and claim T&D compliance, even if both machines heat the fluid through the same mechanism. The testing was done on specific combinations because the aerosol output, particle size distribution, and concentration profile vary with machine design, heating element temperature, pump rate, and output nozzle characteristics (Ramboll, 2024).
For each tested combination, the chart specifies a cue length (the duration for which the machine runs), a distance (the minimum distance from the discharge point at which performers may be positioned), and a wait time (the minimum time after the cue ends before performers may enter the restricted zone). Following all three parameters for a given row guarantees that peak concentrations at the performer’s position will not exceed the guidance levels, based on the conservative testing conditions under which the data was collected (ENVIRON International Corporation, 2001).
The charts include products from a range of manufacturers. Historically tested products include machines and fluids from American DJ, Antari, CITC, Elation Professional, Froggy’s Fog, High End Systems, Le Maitre, Look Solutions, Martin (Harman), MDG, Rosco, and others, with testing conducted by ENVIRON (now Ramboll) over a period spanning from the early 2000s through the most recent additions (Ramboll, 2024).
How Testing Was Conducted
Understanding how the T&D data was generated helps you understand its limitations. ENVIRON conducted the testing in a controlled test environment: a room of specified dimensions with controlled ventilation. Each machine-fluid-attachment combination was operated according to the manufacturer’s instructions for a specified cue duration. Area air monitors were placed at multiple distances from the discharge point, at breathing height (approximately 5 feet). Concentrations were measured over time, and the resulting data was used to determine the minimum distance and wait time at which peak concentrations fell below the applicable guidance level (ENVIRON International Corporation, 2001).
The testing incorporated several conservative assumptions designed to ensure that compliant productions would remain below the guidance levels in real-world conditions. These assumptions include: the fog was discharged at breathing height, which maximizes the concentration at the measurement point (in many actual productions, fog is discharged at floor level or above the stage, where concentrations at breathing height are lower); no on-stage activities, movement, or set pieces were present to enhance aerosol dispersion (in actual productions, performer movement, set changes, and stage mechanics all create air currents that accelerate dispersion); and the test environment’s ventilation was operated at a moderate baseline rate rather than an enhanced rate. These conservative assumptions mean that a production following the T&D charts in a typical theatre with normal ventilation will generally experience peak concentrations well below the guidance levels (ENVIRON International Corporation, 2001).
Reading the Charts: A Practical Walkthrough
A typical T&D chart entry might read as follows (this is a generalized example, not actual chart data):
| Machine | Fluid | Attachment | Cue Length | Min. Distance | Wait Time |
| Manufacturer X Model 500 | Manufacturer X Standard Fog Fluid | None (direct output) | 30 seconds | 10 feet | 3 minutes |
This entry means: when using the Manufacturer X Model 500 machine with Manufacturer X Standard Fog Fluid and no output attachment, you may run the machine for up to 30 seconds continuously. Performers must be at least 10 feet from the discharge point during the cue and must wait at least 3 minutes after the machine stops before entering the 10-foot zone. If your production needs a longer cue, a shorter distance, or a shorter wait time, you must either find a different chart entry that accommodates your needs or switch to the air-sampling compliance path.
Multiple rows may exist for the same machine-fluid combination at different cue lengths. A 15-second cue might require a 5-foot distance and a 1-minute wait, while a 60-second cue with the same equipment might require a 20-foot distance and a 6-minute wait. This scaling reflects the relationship between total aerosol output (which increases with cue duration) and the time required for ambient ventilation to reduce concentrations below the guidance level.
Chart Limitations and Edge Cases
Several real-world scenarios fall outside the T&D chart framework and require air sampling regardless of whether the machine-fluid combination has chart data.
Continuous haze is the most common edge case. Many productions require a constant low-level haze to enhance lighting visibility throughout a show, not a discrete fog cue with a clear start and stop. Continuous haze machines (particularly mineral oil crackers) operate by atomizing fluid at a constant rate over extended periods. The T&D charts were designed for discrete cues with defined cue lengths and recovery periods. A machine running continuously has no “wait time” because there is no pause between cues. This means continuous haze always requires air sampling to verify compliance (Actors’ Equity Association, 2024c).
Ducted fog presents another complication. When fog output is channeled through ductwork, tubing, or scenic elements, the aerosol concentration at the duct exit may be significantly different from the concentration at the machine’s direct output nozzle. Ducting can concentrate the aerosol (if the duct narrows the output path) or reduce it (if the duct allows settling and absorption). Either way, the T&D data was not collected with ducting, so ducted applications require air sampling.
Vertical discharge (upward or downward) changes the relationship between distance and concentration because the aerosol’s vertical trajectory and settling behavior differs from horizontal discharge. A fog machine aimed upward from a floor position or downward from a fly gallery produces a fundamentally different concentration profile at breathing height than a machine aimed horizontally at breathing height, which is how the T&D testing was conducted.
Temperature and humidity extremes can affect aerosol behavior in ways that the testing did not capture. Outdoor summer productions in high heat and humidity, cold-weather touring in venues with minimal heating, and productions in arid climates all present conditions that may cause aerosol concentrations to differ from the test environment baseline. When in doubt, sample.
The “Same Family” Fallacy
A common and potentially costly misunderstanding occurs when a production assumes that two fog machines from the same manufacturer in the same product line can be used interchangeably for T&D purposes. For example, if the T&D chart includes data for the “Manufacturer Y Hazer 800” with “Manufacturer Y Haze Fluid HQ,” a production might assume that the “Manufacturer Y Hazer 1200” (a higher-output model in the same product line) with the same fluid is also covered. It is not.
The higher-output machine produces more aerosol per unit time, may have a different heating element temperature, and almost certainly produces a different particle size distribution. Even if the fluid is identical, the machine determines the aerosol characteristics. Each model requires its own testing data. Using an untested model, even one that appears similar to a tested model, places the production on the air-sampling path.
Common Mistakes with T&D Chart Compliance
In practice, four common errors undermine T&D compliance.
The first error is fluid substitution. A production purchases the correct machine but uses a different fluid, either because the specified fluid is unavailable, because a less expensive alternative is available, or because the operator does not realize that the fluid matters. The T&D data is valid only for the exact fluid tested. A different fluid may produce a different aerosol profile, different particle sizes, and different peak concentrations.
The second error is attachment modification. Many fog machines can be fitted with different output attachments, ducting, or nozzles that change the direction, velocity, and dispersion pattern of the output. If the chart specifies a particular attachment and the production uses a different one, the T&D data does not apply.
The third error is exceeding the specified cue length. The wait times and distances in the T&D charts are based on a specified duration of machine operation. Running the machine longer than the tested cue length produces higher cumulative concentrations and invalidates the chart’s wait-time calculations.
The fourth error is running multiple machines simultaneously without accounting for additive concentrations. The T&D charts are based on single-machine operation. If two machines are running simultaneously in the same space, the aerosol concentrations are additive, and the single-machine chart no longer guarantees compliance. In this scenario, air sampling is required.
Practical Reality Check: If your production uses any fog or haze configuration that does not exactly match a row in the T&D chart, including combinations of machines, cue lengths longer than tested, distances shorter than specified, or multiple simultaneous machines, you are automatically on the air-sampling compliance path. There is no middle ground.
Calibration Factors: The Technical Details
Calibration factors are one of the most technically complex and least well-understood elements of the compliance framework. They exist because portable aerosol monitors do not directly measure mass concentration of a specific chemical. They measure the optical scattering properties of particles in the air, and the relationship between optical scattering and actual mass concentration varies with particle size, shape, refractive index, and chemical composition (Actors’ Equity Association, 2024b).
When ENVIRON (now Ramboll) developed the original testing protocols, they calibrated their monitoring equipment against gravimetric (weight-based) measurements of each specific fog and haze product to determine the correction factor that converts raw monitor readings into accurate mass concentrations. These calibration factors are unique to each product. A monitor reading of 20 mg/m3 raw data might correspond to an actual glycol concentration of 35 mg/m3 for one product and 18 mg/m3 for a different product, depending on the calibration factor.
The April 2024 Calibration Factors memo provides these correction factors for all products included in the testing program. When conducting air sampling, the producer’s representative must either input the calibration factor directly into the monitor before sampling (which allows the monitor to display corrected values in real time) or leave the monitor at a calibration factor of 1.00 (raw data) and multiply the results by the appropriate factor after data collection (Actors’ Equity Association, 2024c).
For productions using multiple fog or haze products simultaneously in a single cue, the calibration process is more complex. Equity’s FAQ addresses this directly: do not calibrate the monitor to a single product if multiple products are in use. Instead, leave the calibration factor at 1.00 to collect raw data, then calculate each product’s effect separately by multiplying the raw data by each product’s specific calibration factor and comparing the results to the appropriate substance-specific guidance level (Actors’ Equity Association, 2024c).
The “Water-Based” Myth: Why It Matters
One of the most consequential clarifications in Equity’s 2024 overhaul addresses a persistent and dangerous misconception in the industry: the belief that “water-based” fog or haze products are inherently safe and exempt from regulatory requirements.
Equity’s FAQ is unambiguous: “All smoke, fog and haze products are ‘water-based’ (e.g., a combination of water and glycol or mineral oil or glycerol)” (Actors’ Equity Association, 2024c). The term “water-based” in fog fluid marketing refers to the fact that water is the primary solvent in the fluid mixture. It does not mean the aerosol is water. When the fluid is vaporized, the glycol, glycerol, or mineral oil components are aerosolized along with the water, and it is these non-water components that pose the respiratory health risk.
A product marketed as “water-based haze fluid” still contains glycol or glycerin at concentrations sufficient to produce a visible atmospheric effect. If it did not contain these active ingredients, it would not produce haze; it would produce steam, which dissipates almost immediately and does not create a lasting atmospheric effect. The “water-based” label has no bearing on the product’s regulatory status, reporting requirements, or exposure-limit applicability (Actors’ Equity Association, 2024c).
This clarification matters because production teams frequently assume that purchasing a “water-based” product eliminates the need for T&D chart compliance, air sampling, or Equity notification. It does not. Every fog and haze product that produces a lasting visible effect in the atmosphere contains an active chemical ingredient that must be evaluated against the published guidance levels.
The PDR-1000AN Discontinuation: A Practical Problem
The entire air-sampling compliance pathway was built around a specific piece of equipment: the PDR-1000AN portable real-time aerosol monitor manufactured by Thermo Fisher Scientific. The T&D testing protocols, calibration factors, and sampling procedures were all developed and validated using this instrument. It was the standard of care for Equity fog and haze compliance monitoring for over two decades.
Thermo Fisher has discontinued the PDR-1000AN, including all spare and replacement parts, and all service and support. Equity’s regulations page acknowledges this directly: “Actors’ Equity is aware that the PDR-1000AN aerosol monitor manufactured by Thermo Fisher Scientific has been discontinued. Discussions with the parties who created the Smoke and Haze Study are underway to add new aerosol monitors for air sampling smoke and haze effects” (Actors’ Equity Association, 2024a).
In the interim, Equity recommends that employers rent rather than purchase the PDR-1000AN (since it is still available through rental houses like Pine Environmental). If the PDR-1000AN is not available at all, productions may still use atmospheric effects provided they strictly adhere to the T&D charts. This means that for productions whose effects fall outside the T&D parameters, the unavailability of the approved monitoring instrument creates a genuine operational problem: you cannot air-sample your way to compliance if the approved monitor does not exist.
This discontinuation is one of the driving factors behind the increased importance of the T&D charts in the 2024 regulatory landscape. It is also why productions need to design their atmospheric effects to fit within the T&D chart parameters whenever possible, rather than planning to air-sample as a fallback.
Two Paths to Compliance
The 2024 framework provides producers with two compliance paths, and only two. There is no third option, no informal middle ground, and no self-certification process.
Path One: Strict Adherence to T&D Charts
If your exact machine, fluid, and attachment combination appears in the approved T&D tables, and your cue length, performer distance, and wait time match the chart parameters precisely, you are compliant without air sampling. This is the simpler, faster, and less expensive path. It requires discipline in equipment selection, cue design, and staging, but it eliminates the need for monitoring equipment, data analysis, and calibration calculations.
The key requirements for T&D chart compliance are: use only the specific machine, fluid, and attachment combination listed in a single row of the chart; do not exceed the specified cue length; do not position performers closer to the discharge point than the specified distance; do not allow performers to enter the restricted zone before the specified wait time has elapsed; maintain the machine according to manufacturer specifications; and use the fluid according to manufacturer specifications (Ramboll, 2024).
Path Two: Air Sampling with Calibrated Monitoring
If your usage falls outside the T&D parameters for any reason, you must conduct on-site air sampling. The requirements for air sampling compliance are: use a portable real-time aerosol monitor (currently the PDR-1000AN, pending approval of alternatives); calibrate the monitor with the specific product’s calibration factor from the April 2024 memo; position the monitor at the location where the closest performers will be staged, choreographed, or positioned relative to the discharge point; take multiple readings before, during, and after each effects cue to establish a median result; download the readings and review the complete data results; verify that peak concentrations do not exceed the guidance levels (40 mg/m3 for glycol, 25 mg/m3 for mineral oil, 50 mg/m3 for glycerol); and send a copy of the data results to Equity at safety@actorsequity.org (Actors’ Equity Association, 2024a; Actors’ Equity Association, 2024c).
Air sampling must commence on the first day when effects are introduced to the stage, and in no event later than technical rehearsals at the theatre.
Practical Application: Pre-Production Planning
Compliance does not start in tech week. It starts in pre-production, and the decisions made during design development and production planning determine whether your atmospheric effects will be compliant, practically achievable, and artistically effective.
Step One: Identify the Effect Requirements
Work with the lighting designer and scenic designer to define the atmospheric effects needed for each scene. Determine whether each effect requires fog (dense, visible cloud), haze (subtle, light-revealing atmosphere), low-lying fog (ground-hugging cryogenic effect), or smoke (combustion particulate). Each type carries different regulatory requirements and different compliance pathways.
Step Two: Select Equipment and Fluids to Match the T&D Charts
Before purchasing or renting any fog or haze equipment, review the current T&D charts and identify which machine-fluid-attachment combinations are listed. Select your equipment to match a tested combination whenever possible. This single decision simplifies the entire compliance process. If the artistic requirements demand a product that is not in the charts, plan for air sampling from the outset and budget accordingly for equipment rental, operator time, and data processing.
Step Three: Design Cues to the Chart Parameters
Once you know which T&D row applies, design your fog and haze cues to stay within the tested parameters. This means specifying the cue length in your cue sheet, establishing the restricted distance zone in your blocking, and building the wait time into your scene transitions. Communicate these parameters to the director and choreographer during the design development phase, not during tech when changes are difficult and expensive.
Step Four: Coordinate with Your Equity Field Representative
Notify Equity in writing of your planned atmospheric effects. If you are using dry ice, liquid CO2, liquid nitrogen, vaporized water, or any substance not listed in the T&D charts, contact your Field Representative directly to determine the applicable compliance requirements.
Step Five: Prepare Documentation
Assemble your compliance file before tech begins. This file should include: the specific machine make and model, the specific fluid product name and lot number, the specific attachment or output configuration, the T&D chart row number that applies (if using Path One), the anticipated cue lengths and distances, and the contract-specific smoke and haze report form.
Practical Application: Tech Week Protocol
Tech week is where compliance theory meets production reality. The following protocol applies whether you are on the T&D chart path or the air-sampling path.
Day One: Effects Introduction
On the first day that atmospheric effects are introduced to the stage, document the machine, fluid, and attachment setup. If air sampling is required, begin monitoring on this day. Position the monitor at the location where the closest performers will be during the effects cues. Run each cue at full show conditions: air circulation running, audience and loading doors closed, and all other production elements operating as they will during performance (Actors’ Equity Association, 2024a).
Throughout Tech: Monitor and Adjust
If you are following T&D charts, verify that the actual cue lengths, distances, and wait times match the chart parameters. If you are air-sampling, take multiple readings across multiple tech runs to establish a median result. If readings exceed the guidance levels, reduce the cue length, increase the distance, extend the wait time, adjust ventilation, or change the product.
Before First Audience: Post and Report
After completing either T&D compliance verification or air sampling, post a notice on the actors’ callboard confirming compliance with the study for the applicable products. Submit the contract-specific smoke and haze report to Equity. If any cues or products change after this report is filed, the notice must be re-posted and the report must be updated in a timely manner (Actors’ Equity Association, 2024a).
Practical Application: Long-Running Shows and Tours
The 2020 revision of ANSI E1.23 specifically addressed the challenge of maintaining atmospheric effects over months or years, and the 2024 Equity updates reinforce the importance of ongoing compliance monitoring (ESTA, 2020).
Long-running shows face several challenges that short-run productions do not: fog machines degrade over time as heating elements accumulate residue; fluid formulations may change between manufacturing lots; building HVAC systems may be adjusted seasonally, altering air circulation patterns in the theatre; replacement machines may not be identical to the original tested equipment; and operator turnover may result in changes to cue execution that affect output levels.
Best practices for long-running show compliance include establishing a periodic recertification schedule (Equity does not specify a frequency, but quarterly verification is a reasonable practice); documenting all machine replacements, fluid lot changes, and HVAC modifications; reconfirming T&D compliance after any significant change to equipment, fluid, or venue conditions; and maintaining a continuous compliance file that travels with the production if it tours.
Special Populations: K-12, Children, and Vulnerable Individuals
The Equity framework and ANSI standards were developed for “otherwise healthy performers, technicians, or audience members of normal working age,” defined by ANSI E1.5 as 18 to 64 years of age (Entertainment Services and Technology Association, 2024). The standards explicitly make no statement about appropriate exposure limits for other populations, and no limits should be inferred from them for children, elderly individuals, or people with pre-existing respiratory conditions.
This creates a significant gap for K-12 educational theatre, community theatre with child performers, and any production that includes audiences or performers outside the “normal working age” demographic. Washington State’s Department of Health addressed this gap directly in its 2023 guidelines, which discourage the use of theatrical fog in school productions altogether and state that “use must be discontinued immediately if any students or staff experience discomfort” (Washington State Department of Health, 2023).
If you work in educational theatre or produce shows with child performers, the following considerations apply beyond the Equity framework: children have smaller airway diameters and higher ventilation rates per unit of body weight than adults, which means they receive proportionally higher doses of inhaled aerosols; children may not recognize or report symptoms of respiratory irritation; individuals with asthma, allergies, or other pre-existing respiratory conditions may react to concentrations well below the adult guidance levels; and the adults supervising children in these settings may not have the training or equipment to monitor exposure levels (Washington State Department of Health, 2023).
Practical recommendations for K-12 and community theatre include: prefer water mist or steam effects where the desired visual can tolerate a short-lived effect; if glycol-based fog is used, follow the Equity T&D charts as a minimum standard even though Equity jurisdiction does not apply; never aim a fog machine directly at performers or the audience; ensure only adults handle fog fluids and operate machines; obtain and review the Safety Data Sheet for any fog product before use; and discontinue use immediately if any performer or audience member reports symptoms (Washington State Department of Health, 2023).
The Role of Ventilation and Engineering Controls
Ventilation is the single most important engineering control for managing atmospheric effect concentrations in performance spaces. The rate at which fresh air enters a space and the rate at which aerosol-laden air is exhausted directly determines how quickly peak concentrations dissipate after a cue and the baseline ambient concentration during periods of continuous haze.
The T&D charts were developed under the assumption that the venue’s existing HVAC system is operating at its normal capacity, with no additional on-stage ventilation or enhanced dispersion from set pieces or actor movement. This means the charts represent a conservative baseline. Productions with better ventilation may see concentrations drop below the guidance levels faster than the charts predict, while productions in spaces with poor ventilation or recirculating air systems may experience higher concentrations than expected (ENVIRON International Corporation, 2001).
Key ventilation principles for atmospheric effects management include: run the venue’s HVAC system during tech and performance whenever atmospheric effects are in use, even if running the HVAC affects the visual quality of the fog; recognize that recirculating HVAC systems (which filter and return indoor air) are less effective at reducing aerosol concentrations than systems that introduce fresh outdoor air; position exhaust vents or fans downstage or at performer level to help clear aerosols from the breathing zone; recognize that orchestra pits, basement-level trap rooms, and below-stage spaces are particularly vulnerable to aerosol accumulation because many fog and haze particles are denser than ambient air; and consult with the venue’s HVAC engineer if you plan to use atmospheric effects extensively (Teschke et al., 2005; Actors’ Equity Association, 2024a).
ANSI E1.23 provides additional guidance on ventilation strategies, including the consideration of portable air filtration units for venues with inadequate HVAC capacity (ESTA, 2020).
International Perspectives: Canada, the UK, and Beyond
The Equity and ANSI framework governs U.S. productions, but international standards and research provide useful context and sometimes more conservative protections.
Canada
The most comprehensive non-U.S. research comes from Canada, where Actsafe Safety Association (British Columbia’s health and safety association for the arts and entertainment industries) and the University of British Columbia have published extensive reports on atmospheric effects exposure and health effects (Actsafe Safety Association, 2003). The Varughese et al. (2005) and Teschke et al. (2005) studies discussed earlier were conducted in British Columbia. IATSE has been active in requesting additional research, including commissioning Aura Health and Safety Corporation and UBC to develop calibration factors for fog and haze products commonly used in the Canadian film industry (Actsafe Safety Association, 2022). Canada’s Workers’ Compensation Board exposure limits for mineral oil mists are significantly more restrictive than U.S. levels; the 8-hour exposure limit for mildly refined oils is 0.2 mg/m3, compared to the ACGIH TLV of 5 mg/m3 (Actsafe Safety Association, 2003).
Motion Picture and Television
The motion picture industry operates under a separate regulatory framework. The Industry-Wide Labor-Management Safety Committee publishes Safety Bulletin #10, “Guidelines Regarding the Use of Artificially Created Atmospheric Fog and Haze,” and its companion Addendum A, which provide industry-specific guidance for film and television productions (Safety Bulletin #10, 2019). These guidelines are referenced in IATSE and SAG-AFTRA agreements and address issues specific to film production, including prolonged continuous haze for lighting consistency across takes and the use of atmospheric effects in confined set environments.
What This Means for Non-Equity Productions
If you work in community theatre, educational theatre, non-union regional theatre, corporate events, or any other non-Equity context, Equity’s regulations do not have contractual force over your productions. You are not required to file smoke and haze reports with Equity, follow the T&D charts, or use approved monitoring equipment.
You are, however, still responsible for the health and safety of everyone in your venue.
ANSI E1.5 and E1.23 apply to “theatres, arenas, and other places of entertainment or public assembly where theatrical fogs and mists are often used” (Entertainment Services and Technology Association, 2024). These are nationally recognized consensus standards, and adherence to them represents the standard of care that a reasonable professional would follow. In a liability context, failure to follow ANSI standards when they are applicable and readily available is a difficult position to defend.
Best practices for non-Equity productions include: treat the ANSI E1.5 exposure limits as your minimum safety standard; use the Equity T&D charts as operational guidance, even though you are not contractually bound by them; follow ANSI E1.23 for planning, execution, and maintenance of atmospheric effects; select approved machine-fluid-attachment combinations whenever possible; document your atmospheric effects usage and any health complaints received; and pay particular attention to the special populations guidance if children, elderly individuals, or people with known respiratory conditions are present.
Fire Alarm Integration and Emergency Considerations
Theatrical fog and haze can trigger smoke detectors, and this creates a safety management challenge that sits at the intersection of fire code compliance and atmospheric effects design. ANSI E1.23 identifies the prevention of false fire alarms as one of its primary interests (ESTA, 2020). A common practice is to conduct a “smoke test” in which the venue is filled to capacity with fog to identify any smoke detectors that are still active or any leaks through which fog could reach detectors in other parts of the building.
Disabling or modifying smoke detectors for theatrical purposes requires coordination with the local fire marshal and the venue’s fire alarm monitoring company. In many jurisdictions, detectors cannot be disabled without providing alternative fire watch procedures, which may include posting trained fire watch personnel in affected areas for the duration of the performance. The specific requirements vary by jurisdiction and should be confirmed with the authority having jurisdiction (AHJ) before tech begins.
Emergency egress is another consideration. Dense fog effects can reduce visibility to the point where performers, crew, or audience members cannot see exit signs, aisle lighting, or egress paths. ANSI E1.23 addresses this concern and recommends that emergency egress plans account for atmospheric effects that may reduce visibility during an evacuation (ESTA, 2020).
The Future of Atmospheric Effects
Several trends are shaping the next chapter of theatrical fog regulation and technology.
The most immediate concern is the resolution of the monitoring instrument gap created by the PDR-1000AN discontinuation. Equity has stated that discussions are underway with the parties who created the Smoke and Haze Study to approve new aerosol monitors (Actors’ Equity Association, 2024a). The selection of a new standard instrument will need to include validation testing and the development of corresponding calibration factors. Until this process is complete, the industry is operating in a transitional period where the T&D charts carry even more weight as the primary compliance tool.
Advances in fog and haze machine technology continue to expand the range of products available, which creates ongoing pressure to update the T&D charts as new machine-fluid combinations enter the market. The 2024 charts already include products tested by Ramboll as recently as 2023 (Ramboll, 2024), and this cycle of testing and chart expansion is likely to continue.
LED and projection technology advances are reducing the need for atmospheric haze in some lighting applications. Where haze was once the only way to make a beam visible, LED arrays, holographic screens, and laser-safe architectural lighting can now achieve beam-in-air effects without introducing any substance into the atmosphere. While these technologies will not eliminate the need for atmospheric effects in theatrical storytelling, they may reduce the frequency and intensity of haze usage in concert and corporate event applications.
Finally, the growing body of research on long-term chronic exposure effects may eventually prompt a revision of the guidance levels themselves. The current limits were established based on the data available in 2000 and have not been updated to reflect the additional evidence accumulated over the past 25 years. Whether the limits should become more restrictive, remain where they are, or be differentiated further by substance type is a question that occupational health researchers will need to address.
Your Complete Action Plan
Theory is useful. Action is essential. Here is the complete, step-by-step compliance framework for your next production.
Pre-Production (4-8 Weeks Before Tech)
Tech Week
During the Run
Document everything. Maintain a compliance file that includes: T&D chart references, air sampling data (if applicable), calibration records, the callboard notice, the Equity report, and correspondence with your Field Representative.
Re-certify after changes. If any cue, product, machine, or venue condition changes after the initial compliance verification, re-verify compliance, re-post the callboard notice, and update the Equity report.
For long-running shows: Establish a periodic recertification schedule. Document all machine replacements, fluid lot changes, and HVAC modifications. Reconfirm compliance after any significant change.
Respond to complaints. If any performer reports respiratory symptoms, take the complaint seriously. Re-verify compliance, increase ventilation, reduce cue intensity, and document the complaint and your response. Contact your Equity Field Representative if needed.
The Bottom Line
Atmospheric effects are not going away. Equity is not trying to ban fog. The regulatory philosophy is clear: limit peak exposures through engineering controls such as positioning, cue design, and ventilation; verify compliance through either pre-tested T&D charts or calibrated air sampling; and keep the union formally in the loop on what you are doing (Ramboll, 2024).
What is changing is the tolerance for ambiguity. The “water-based means safe” assumption is dead. The “we have always used this fluid” justification is insufficient. The assumption that fog machines are plug-and-play consumer devices that require no safety planning is exposed as irresponsible.
The expectation now is documentation, specificity, and accountability. The science supports it. The standards define it. The contract requires it. And the health of the performers standing in that beautiful, light-catching haze depends on it.
For those of us who care about both the art and the people who make it, this is a welcome development. Beautiful stage pictures and safe working environments are not competing interests. They never were. The 2024 updates simply make that principle enforceable.
References
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