Acetone is a clear, colorless liquid and one of the most common organic solvents used globally. While widely recognized as the primary component in many nail polish removers, it is also used in manufacturing plastics, fibers, and pharmaceuticals. Acetone is classified as highly flammable, posing a significant fire risk if not handled with appropriate caution.
Defining Flammability: Acetone’s Chemical Profile
Acetone’s flammability stems from its chemical characteristics, allowing it to ignite easily and sustain combustion. The primary factor is its extremely low flash point, the minimum temperature at which the liquid releases enough vapor to form an ignitable mixture with air. Acetone’s flash point is approximately 0°F (-18°C), meaning it releases flammable vapors and can ignite even at room temperature.
The National Fire Protection Association (NFPA) classifies acetone as a Class 1B flammable liquid, indicating a significant fire hazard. This classification applies to liquids with a flash point below 73°F (22.8°C) and a boiling point above 100°F (37.8°C), placing it in the most hazardous category of common solvents.
Acetone’s vapor density is about two times heavier than air. This causes the vapors to sink and travel along floors or low-lying areas instead of dissipating quickly. These traveling vapors can find a distant ignition source, such as a pilot light, and cause a “flashback” fire that travels back to the liquid source.
For ignition to occur, the vapor concentration must fall within the Flammable Limits in Air, ranging from a Lower Explosive Limit (LEL) of 2.5% to an Upper Explosive Limit (UEL) of 12.8%. This wide range means that a small amount of vapor mixing with air can quickly create an explosive atmosphere.
Immediate Hazards and Safety Risks
The hazards of using acetone stem from the ease with which its vapors ignite, creating fire and explosion risks. Because the flash point is low, opening a container near a heat source, electrical spark, or open flame can trigger ignition. Vapors released from even a small spill can quickly fill a confined area.
When vapors accumulate, such as in a basement or storage tank, the mixture can become explosive. The resulting vapor cloud explosion is far more destructive than a simple liquid fire. Containers of acetone exposed to fire or high heat may also rupture violently due to internal pressure buildup.
Acetone also carries inhalation and contact risks, especially in poorly ventilated environments. High concentrations of vapor can irritate the respiratory tract, eyes, and mucous membranes, leading to symptoms like dizziness and headache. Prolonged skin contact can cause defatting of the skin, resulting in dryness and dermatitis.
Safe Handling, Storage, and Emergency Response
Handling
Mitigating the flammability of acetone requires strict adherence to safety protocols. When handling the liquid, ensure the area has adequate ventilation, ideally using a fume hood, to prevent vapor accumulation. All ignition sources, including cigarettes, hot surfaces, and static discharge, must be eliminated from the work area. To prevent static sparks during transfer, metal containers and receiving equipment must be electrically bonded and grounded.
Storage
Proper storage involves keeping acetone in tightly sealed containers that are cool, dry, and well-ventilated, away from direct sunlight and heat sources. It must be stored separately from incompatible materials, such as strong oxidizing agents, acids, and alkalis, as contact can cause fire or explosion. For larger quantities, dedicated flammable liquid storage cabinets are necessary to isolate the hazard.
Emergency Response
In the event of a small spill, immediately remove all ignition sources and ventilate the area. The liquid should be contained and soaked up using a non-reactive absorbent material like sand or inert absorbent, then placed in a sealed container for disposal.
For fire emergencies, the appropriate extinguishing agents are carbon dioxide (CO2), dry chemical powder, or alcohol-resistant foam, as acetone is a Class B fire. A straight stream of water should never be used, as this can spread the burning liquid. However, a water fog can be used to cool fire-exposed containers from a safe distance.