Flammable and combustible liquids are present in virtually every performing arts facility: paint thinners and brush cleaners in the paint shop, contact cements in the scene and costume shops, acetone for mold release and adhesive cleanup, alcohol-based makeup removers in the dressing rooms, and fuel for special effects. These liquids catch fire easily and, once ignited, burn intensely. Flammable liquid fires are fast-moving and produce hot, often toxic smoke. Understanding how flammable liquids ignite, how they are classified under NFPA 30 (the Flammable and Combustible Liquids Code), and how to store and handle them correctly is essential safety knowledge for anyone working in a performing arts production environment.

How Flammable Liquids Catch Fire

A common misconception is that the liquid itself burns. In fact, it is the vapor above the liquid surface that ignites. Flammable liquids evaporate continuously, producing invisible vapor that mixes with air. When the vapor-air mixture reaches the right concentration and encounters an ignition source (an open flame, a spark, a hot surface, static electricity), it ignites — sometimes explosively. Two key concepts define this behavior:

• Flash Point: the lowest temperature at which a liquid produces enough vapor to briefly ignite when an ignition source is applied. Below the flash point, the liquid does not produce sufficient vapor to sustain ignition. Above the flash point, any ignition source can cause a flash fire. The flash point is the single most important number for understanding a flammable liquid’s fire hazard.
• Flammable Range (Explosive Limits): the range of vapor-air concentrations that will support combustion. Below the Lower Flammable Limit (LFL), the mixture is too lean (not enough vapor). Above the Upper Flammable Limit (UFL), the mixture is too rich (not enough oxygen). Only within the flammable range will the mixture ignite. The LFL is particularly important: for many flammable liquids, the LFL concentration in air is detectable by smell (though relying on smell is not a safe monitoring strategy).

NFPA 30 Classification: Class I, II, and III Liquids

NFPA 30 (Flammable and Combustible Liquids Code) classifies liquids by their flash points and boiling points. This classification system determines storage, handling, and use requirements. The three main classes:

Class I: Flammable Liquids

Flash point below 100 degrees F (37.8 degrees C). Class I liquids produce flammable vapors at room temperature and below. They are the highest-hazard category. Class I is further divided:

• Class IA: flash point below 73 degrees F (22.8 degrees C), boiling point below 100 degrees F. Examples: ethyl ether, pentane, carbon disulfide.
• Class IB: flash point below 73 degrees F, boiling point at or above 100 degrees F. Examples: acetone (flash point -4 degrees F), isopropyl alcohol (flash point 53 degrees F), methyl ethyl ketone, toluene, naphtha.
• Class IC: flash point at or above 73 degrees F but below 100 degrees F. Examples: turpentine (flash point approximately 95 degrees F), some xylene formulations.

Common performing arts materials in Class I include: acetone, isopropyl alcohol, naphtha, mineral spirits with low flash point, contact cement solvents, and many spray paint propellants.

Class II: Combustible Liquids

Flash point at or above 100 degrees F but below 140 degrees F. Class II liquids do not produce flammable vapors at normal room temperature, but can ignite when heated. Examples: kerosene (flash point approximately 100-130 degrees F), mineral spirits with higher flash point formulations, some diesel fuels.

Class III: Combustible Liquids

Flash point at or above 140 degrees F. Class IIIA: 140-200 degrees F. Class IIIB: at or above 200 degrees F. Examples: motor oil, linseed oil (flash point approximately 500 degrees F), mineral oil. Lower fire hazard at ambient temperature but still require appropriate handling when heated.

Storage Requirements Under NFPA 30

NFPA 30 sets maximum quantities of flammable and combustible liquids that may be stored in non-sprinklered rooms (and higher limits for sprinklered rooms). The key threshold for performing arts spaces:

• No more than 25 gallons of Class I liquids may be stored outside of an approved flammable storage cabinet in a sprinklered room. In a non-sprinklered room, the limit is 10 gallons.
• Approved flammable materials storage cabinets (FM-approved or UL-listed) are constructed of double-wall 18-gauge steel with a 3-point latch, liquid-tight sill to contain spills, and venting provisions. These cabinets are labeled “FLAMMABLE — KEEP FIRE AWAY.” Ventilation of flammable cabinets is optional under NFPA 30 — unvented cabinets may actually be safer because they contain vapors that would otherwise enter the room.
• Flammable liquid storage rooms (dedicated flammable storage rooms meeting NFPA 30 construction requirements) allow larger quantities but require fire-rated construction, explosion-proof electrical, spill containment, and automatic fire suppression.
• Flammable liquids must not be stored in basements (vapor-air mixtures are heavier than air and will accumulate in low spaces).

In the performing arts context, the practical implication is that small program quantities (a gallon of acetone, a gallon of mineral spirits, a quart of contact cement solvent) should be stored in an approved flammable cabinet when not in active use. Larger accumulations require a proper flammable storage room or must be reduced.

Approved Containers

Flammable liquids must be stored in approved containers. NFPA 30 specifies the maximum container sizes for various liquid classes and container materials:

• Safety cans: FM-approved or UL-listed spring-loaded, self-closing lid safety cans are the recommended containers for flammable liquid storage and dispensing in quantities up to 5 gallons. Safety cans have flame arresters in the spout to prevent flashback ignition.
• Glass containers: permitted for quantities up to 1 quart for Class IA, IB, and IC liquids when a safety can would be unsuitable (e.g., for chemical compatibility or laboratory applications).
• Original manufacturer containers: unopened containers in original packaging are acceptable. Once opened, transfer to a safety can for ongoing use.
• Never use food or beverage containers for flammable liquid storage. An acetone-filled water bottle is an accident waiting to happen.
• Containers must be kept tightly closed when not in use. Open containers allow vapor to accumulate in the room air.

Dispensing and Use

Most flammable liquid fires in workplaces occur during dispensing, transfer, and use — not during storage. Hazard controls for dispensing and use:

• Bonding and grounding: when transferring flammable liquids from one metal container to another, static electricity can accumulate on the receiving container and discharge, igniting the vapor. Metal containers should be bonded (connected with a wire) before transfer, and at least one container must be grounded to earth. This is required under OSHA 29 CFR 1910.106(e)(6)(ii) for dispensing from containers larger than 5 gallons.
• Eliminate ignition sources: dispense flammable liquids only in areas free of open flames, cigarettes, unprotected electrical switches and outlets, and other ignition sources. This includes pilot lights in nearby equipment.
• Quantity minimization: keep only the quantity needed for the immediate work in the work area. Return containers to the flammable cabinet when not in active use. Never leave open containers of flammable liquids unattended.
• Ventilation: ensure adequate dilution ventilation when using Class I flammable liquids. Measure adequacy by the absence of solvent odor at head height (though olfactory fatigue can eliminate the odor sensation even at dangerous concentrations — ventilation must be engineered, not just sensed).
• Spill response: flammable liquid spills must be cleaned up immediately. Use non-sparking tools to spread absorbent (kitty litter, dry sand) over the spill. Collect absorbent in a metal container with a tight lid. Do not sweep a solvent spill with a dry broom (friction and static).

Solvent-Soaked Rags and Spontaneous Combustion

Spontaneous combustion is a real and recurring cause of fires in theater facilities. It occurs when rags, shop towels, or paper products saturated with certain flammable or combustible liquids are piled or crumpled together. The oxidation of the solvent generates heat; if the heat cannot dissipate (because the rags are piled), the temperature climbs until the material ignites — without any external ignition source.

Drying oils (linseed oil, tung oil, danish oil, and oil-based varnishes that contain these oils) are the primary spontaneous combustion risk. Mineral spirits and acetone do not present the same spontaneous combustion risk but are fire hazards if stored improperly. Required practices:

• Solvent-soaked rags used with drying oils must be spread flat in a single layer to cool and dry, or placed in a listed self-closing metal safety container (oily waste can) with water covering the rags.
• The metal oily-waste can must be emptied daily and the contents disposed of properly.
• Never pile oil-soaked rags in a corner, in a trash can, or in a plastic bag.
• The distinction between “safe for 20 minutes” and “fire overnight” has destroyed theater facilities. This is not a theoretical hazard.

Compressed Aerosol Products

Many performing arts products are packaged as aerosol sprays: spray paint, adhesive sprays, mold release sprays, hair and makeup sprays, and special effects products. Aerosol cans present a dual hazard: the propellant (typically a mixture of hydrocarbons or CO2) is often flammable, and the can is pressurized and can rupture if exposed to heat or physical damage.

• Aerosol cans must not be stored near heat sources, in direct sunlight, or at temperatures above 120 degrees F.
• Never puncture, incinerate, or crush aerosol cans, even if they appear empty.
• Aerosol cans with flammable propellants must not be used near open flames, pilot lights, or other ignition sources.
• Dispose of empty aerosol cans through the regular solid waste stream only after ensuring they are fully empty (shake to check; no residual spray sound).
• Aerosol spray painting generates fine mist in the air that is both an inhalation hazard and a fire hazard. Spray painting with aerosols must be done in ventilated conditions away from all ignition sources.

Key Takeaways

• Flammable liquid vapor — not the liquid itself — ignites. The flash point tells you at what temperature a liquid generates enough vapor to ignite. Class I flammable liquids (flash point below 100 degrees F) generate flammable vapor at room temperature.
• NFPA 30 limits Class I flammable liquids to 10 gallons in a non-sprinklered room or 25 gallons in a sprinklered room outside a storage cabinet. Exceed these limits with an FM-approved storage cabinet or dedicated flammable storage room.
• Use safety cans with flame arresters for dispensing flammable liquids. Original manufacturer containers are acceptable when unopened; transfer contents to a safety can once opened.
• Bond and ground metal containers when transferring flammable liquids in quantities over 5 gallons to prevent static discharge ignition.
• Rags soaked with drying oils (linseed, tung, danish oil, oil-based varnishes) can spontaneously combust when piled. Spread flat to dry, or submerge in water in a listed oily-waste can emptied daily.
• Aerosol cans with flammable propellants must be kept away from heat and ignition sources. Never puncture or incinerate aerosol cans.

References

National Fire Protection Association. (2021). NFPA 30: Flammable and combustible liquids code. NFPA.

Occupational Safety and Health Administration. (n.d.). Flammable liquids. 29 CFR 1910.106. U.S. Department of Labor.

National Fire Protection Association. (2021). NFPA 1: Fire code. NFPA. (Chapter 66: Flammable and Combustible Liquids)

Rossol, M. (2001). The artist’s complete health and safety guide (3rd ed.). Allworth Press.

Factory Mutual Research. (2021). FM Global property loss prevention data sheet 7-29: Flammable liquid storage. FM Global.

Was this article helpful?

0 out of 5 stars

5 Stars		0%
4 Stars		0%
3 Stars		0%
2 Stars		0%
1 Stars		0%

5 Submit

Please Share Your Feedback

How Can We Improve This Article?

Name

Email

Submit