According to the EPA, while combustible and flammable liquids are classified differently, they both fall under the category of ignitable hazardous waste. That means you must follow specific regulations and guidelines for storing, organizing, and disposing of these materials.
To help you understand the difference between combustible and flammable liquids, our guide identifies their differing flash points, common materials, and what the NFPA says about producers of these products.
What Is a Flash Point?
The flash point is the lowest temperature at which a material’s vapors ignite if given an ignition source. It is used to determine whether a material is classified as flammable or combustible.
Combustible Materials
Combustible materials are substances that catch fire when exposed to specific ignition triggers. According to the NFPA, a combustible liquid is defined as a liquid with a flashpoint at or above 100°F (37.8°C) but below 200°F (93.3°C), which is higher than what is necessary for a flammable liquid. Before a combustible material becomes a fire risk, it must be heated (or stored in a warm space).
Because of the required higher temperature, they are less volatile than flammable liquids.
There’s always the risk of spontaneous combustion as well. Spontaneously combustible materials, also known as pyrophoric, cause fires when the combustible materials self-heat to a temperature high enough for ignition to occur.
Materials such as rags and towels soaked with oils, including cooking oils; hot laundry left in piles; large compost, mulch, manure, and leaf piles all carry combustible risks that you should be aware of depending on your business.
What are common combustible materials?
- Diesel Fuel – Flashpoint: 52°C to 82°C (126°F to 180°F)
- Kerosene – Flashpoint: 38°C to 72°C (100°F to 162°F)
- Fuel Oils (e.g., No. 1 and No. 2 fuel oil) – Flashpoint: Approximately 52°C (126°F) for No. 1 and 52°C to 82°C (126°F to 180°F) for No. 2
- Hydrazine – Flashpoint: 52°C (126°F)
- Naphthalene – Flashpoint: 78.89°C (174°F)
- Phenol – Flashpoint: 79°C (174°F)
Formic Acid – Flashpoint: 69°C (156°F) - Cyclohexane – Flashpoint: 32.8°C (91°F)
- Paint Thinner – Flashpoint: 40°C (104°F)
- Turpentine – Flashpoint: 35°C (95°F)
- Mineral Spirits – Flashpoint: 38°C (100°F) to 62°C (144°F)
Flammable Materials
Like combustible materials, flammable materials catch fire near an ignition source. The biggest difference is the low flash point, typically below 100°F (37.8°C), which causes issues under normal conditions.
These materials are more volatile in part because they can ignite in nearly any setting, including your home, commercial building, or industrial environment.
The biggest risk associated with flammable materials comes from their ability to form explosive mixtures with air. When a flammable liquid reaches its flashpoint, it emits vapors that, when mixed with air, can ignite and cause rapid combustion if the right ignition source is present.
What are common flammable materials?
- Gasoline (Petrol) – Flashpoint: -43°C (-45°F)
- Ethanol (Ethyl Alcohol) – Flashpoint: 16.6°C (62°F)
- Methanol – Flashpoint: 12°C (54°F)
- Acetone – Flashpoint: -20°C (-4°F)
- Isopropyl Alcohol (Isopropanol) – Flashpoint: 12°C (54°F)
- Benzene – Flashpoint: -11°C (12°F)
- Propylene Oxide – Flashpoint: -37°C (-35°F)
- Ethyl Acetate – Flashpoint: -4°C (25°F)
- Toluene – Flashpoint: 4°C (39°F)
- Hexane – Flashpoint: -22°C (-8°F)
- Heptane – Flashpoint: -4°C (25°F)
- Butane – Flashpoint: -60°C (-76°F)
- Propane – Flashpoint: -104°C (-155°F)
Volatility and Ignition Temperature
There are two key ingredients when determining the fire hazard potential of a material: volatility and ignition temperature.
Volatility refers to a substance’s tendency to vaporize at a given temperature. Highly volatile substances easily transition from a liquid or solid state to a gaseous state, with each transition increasing the risk of creating an ignitable mixture.
Ignition temperature is the minimum temperature required for a substance to spontaneously ignite without an external ignition source, such as a flame or spark.
When combined, these cause fire risks throughout your building. A highly volatile material with a low ignition temperature could start a fire at any point, so you need to keep these products stored safely and securely to avoid serious problems.
Regulatory Overview
The EPA’s oversight is primarily governed by the Resource Conservation and Recovery Act (RCRA), which sets the guidelines for properly handling, storing, and disposing of hazardous wastes.
Under the RCRA, flammable and combustible materials are classified as ignitable hazardous wastes. These include liquids with flash points below 60°C (140°F) for flammable materials and those between 60°C (140°F) and 93.3°C (200°F) for combustible materials
The EPA mandates specific handling and storage requirements, including using appropriate containers, proper labeling, and adequate ventilation in storage areas to prevent the accumulation of vapors
There must also be an emergency response plan in place if your business handles large quantities of these materials.
Additionally, facilities that handle significant quantities of these materials must have emergency response plans and safety protocols to address potential incidents.
To avoid the mixing of substances, the EPA requires the disposal of combustible and flammable materials through the use of a trained hazardous waste disposal company.
NFPA Standards
NFPA 30, the Flammable and Combustible Liquids Code, outlines the necessary storage, handling, and disposal precautions to prevent fires and explosions. There are three main factors to consider: storage, disposal, and spill control.
Storage Requirements
Flammable and combustible liquids must be stored in approved containers and cabinets designed to prevent ignition. These containers should be metal, as plastic ones can potentially cause static shock and start fires.
All storage areas need a fire suppression system and proper ventilation to disperse vapors to limit fire risk.
Disposal Procedures
Disposal of flammable and combustible wastes must follow protocols that ensure the materials are not mixed with incompatible substances.
The NFPA emphasizes the need for proper labeling and segregation of waste to prevent hazardous reactions.
Spill Control
Buildings must have spill containment measures to avoid the accidental release of flammable or combustible liquids. These measures include spill pallets and absorbent materials.
Need Help Disposing of Flammable or Combustible Liquids? Reach Out to HWH Environmental Today.
Whether you have flammable liquids, need hand sanitizer disposal, or want help removing AFFF from your fire station, HWH Environmental has you covered. With decades of experience, the team at HWH Environmental works with you to avoid harmful consequences and unnecessary fines.
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