Flammable and Combustible Liquid Storage and Handling

Mitigating Ignitable Liquid Hazards

Despite the name, flammable liquids don’t actually burn. Vapors released by the liquids burn. Flammable and combustible liquid vapors are usually heavier than air, so they accumulate with the greatest concentration near the liquid’s surface at low points of a spill area.

With oxygen also present in most such areas, you just need a spark or other heat source to get a fire or explosion. These types of fires release heat rapidly and can easily spread if the liquids are not confined. A compounding problem is that, controlling liquid spread can be difficult. Confined vapors that ignite can result in an explosion with pressure wave damage. Due to these factors, a solid property risk engineering program is integral to mitigating against these hazards.

Flammable Liquid Classifications

A liquid’s Flash Point (FP) is the primary characteristic for classification. The Flash Point of a liquid is the lowest temperature at which the vapors released from the liquid will ignite. “Flammable” liquids have Flash Points at or below room temperature. Common examples of flammable liquids include acetone and gasoline.

Vapors from “combustible” liquids need to be heated above room temperature to ignite easily. That heating can be done in a small volume, like with a match that heats the vapor next to it, so you can ignite many combustibles “at room temperature” if you have a large enough heat source. Most liquids referred to as flammable in industry and households are technically “combustible.” These include diesel fuel, alcohols, and most oils – whether petroleum or vegetable. As a result of general confusion around the terms “flammable” and “combustible,” there is now a move to refer to all such liquids as “ignitable liquids.”

Classification of flammable and combustible liquids vary depending on the organization. NFPA’s classifications are the most common.

NFPA 30 Classification Is As Follows:

• Class IA Flammable Liquid: Flash Point <73 °F (22.8 °C), Boiling Point of < 100 °F (37.8 °C)
• Class IB Flammable Liquid: Flash Point <73°F (22.8° C), Boiling Point of ≥ 100 °F (37.8 °C)
• Class IC Flammable Liquid: Flash Point ≥ 73 °F (22.8°) and ≤ 100 ˚F (37.8 ˚C), Boiling Point of ≥ 100 °F (37.8 °C)
• Class II Combustible Liquid: Flash Point ≥ 100 °F (37.8 °C), and < 140 °F (60 °C)
• Class IIIA Combustible Liquid: Flash Point ≥ 140 °F (60 °C) and < 200 °F (93 °C)
• Class IIIB Combustible Liquid: Flash Point ≥ 200 °F (93 °C)

Expertise In Proper Handling and Storage

Preventing ignitable liquid fires focuses on controlling the use of the liquid to prevent its release, especially where ignition sources are known to be present. Basic steps to take include:

• When ignitable liquids are not in use, they should be stored in flame-resistant flammable storage cabinets or specially designed flammable liquid storage rooms. They should always be separated from other hazardous chemicals and properly labelled.
• Systems using flammable and combustible liquids should be housed in dedicated areas, separated from general storage areas. All components should be well bonded/grounded with leak prevention and detection systems
• Appropriate safety interlocks need to be provided when anomalous conditions are detected.
• Electrical and mechanical equipment used in areas where flammable liquids are present should be rated for those environments.
• All areas using or storing ignitable liquids should be provided with safety ventilation.
• Appropriate human element programs such as hot work permits, smoking controls, and regular equipment/area inspections should be implemented.

Engineering systems to control the potential damage from a fire or explosion involving flammable liquids is a complex process. Items that need to be considered include:

• Fire rating of construction
• Appropriate fire suppression systems.
• Should sprinklers, foam, or a clean agent system be provided?
• Explosion venting considerations

TÜV SÜD Global Risk Consultants (GRC) experts are on-hand to assist you in identifying your fire and explosion risk exposures. We help implement a proactive property risk engineering plan in case of such events. Our fire prevention efforts are unmatched and property loss control engineers are world class. We have 87 Fortune 500 clients, conducted 56,000 onsite engagements, and have serviced facilities valued at more than $4 trillion.

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