Storing & Handling Flammable and Combustible Substances


SPEC frequently works with clients that store some amount of flammable and/or combustible substances.  Obvious substances like gasoline and diesel fuel are flammable and combustible but even common products, such as polishes, waxes, adhesives, paints, cleaners, solvents, and thinners can pose a threat.  Ensuring that such products are properly stored, especially in an industrial workplace, can protect against serious fire or injury.  The NFPA and state and local building codes provide regulations and standards to employers for the handling and storage of flammable and combustible liquids.Our clients frequently ask for clarification and assessment regarding the appropriate storage and handling of potentially dangerous substances.   We thought it would be useful to highlight some key information.The first step for proper handling is to understand the hazard category of a particular substance.

Combustible liquids have a flashpoint at or above 100° F. Combustible liquids are subdivided into Class II or Class III liquids.

  • Class II liquids, like diesel fuel, fuel oil, and motor oil, have a flashpoint between 100° F and 140°F.
  • Class III liquids are split into Class IIIA and Class IIIB.
  • Class IIIA liquids include furfural, linseed oil, mineral oil, and oil based pants, which have a flashpoint between 140° F and 200°.
  • Class IIIB liquids, with a flashpoint over 200° F, include ethylene glycol and glycerin

Flammable liquids
 have a flashpoint below 100° F.  Flammable liquids are subdivided into Class IA, IB, or IC.

  • Class IA liquids have a flashpoint below 73° F and a boiling point below 100° F.  These include ethyl ether, heptane, pentane, and vinyl chloride.
  • Class IB liquids have a flashpoint below 73° F and a boiling point above or equal to 100° F.  These include acetone, ethanol, gasoline, isopropyl alcohol, and octane.
  • Class IC liquids have flashpoints between 73° F and 100° F and no specific boiling point.  They include isobutyl alcohol, mineral spirits, and turpentine.

Once the type (i.e. Class) and desired quantity for use and storage of substance has been determined, the requirements for proper handling and storage can be evaluated.

Ultimately though, the final use of a flammable or combustible liquid can be the true source of hazard.  With these substances, the vapor, not the liquid, is what burns.  For example, an emptied gasoline tank can still contain gasoline vapors, and may explode when an ignition source is introduced.  Consequently, certain procedures must be followed when handling flammable and combustible liquids:

  • Store flammable and combustible liquids only in acceptable containers.
  • Ensure that locations where flammable vapor-air mixtures may exist have appropriate electrical wiring installed, have the proper fire separation rating, ventilation, sprinkler requirements, etc.
  • Maintain tools necessary to dispose of leaked or spilled liquids promptly and safely.
  • Provide adequate ventilation for transfer operations but do not permit sources of ignition in areas where flammable vapors may travel.
  • Do not transfer liquids by air pressure on the container or portable tanks.
  • When unsure about the appropriate procedure, refer to 29 CFR 1910.106 as well as NFPA 30 Flammable and Combustible Liquids Code or consult a professional.

We hope this information provides a good starting point for understanding flammable and combustible liquids so that industrial users and others can make their own assessment to involve professional help or address the issue themselves to maintain a safe work environment.  Please look for future posts that will explore this topic in greater detail.  You can also post questions about this and similar topics on our forum.


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