Flammable vs Inflammable – Why They Mean the Same Thing


Difference between flammable, inflammable, and nonflammable.
Flammable and inflammable both mean “easily ignited” while nonflammable means “not easily set on fire.”

Flammable and inflammable are two words with the same meaning. They are synonyms. Both words mean “easy to ignite or set fire to.” Flammable and inflammable substances are also called combustible materials. The antonym or word that means the opposite of flammable and inflammable is nonflammable. Technically, “nonflammable” means a substance is incapable of catching fire. But, everything burns if you apply enough energy, so nonflammable means a material is flame retardant or difficult to ignite.

Why Flammable and Inflammable Have the Same Meaning

Flammable, inflammable, and combustible all mean “capable of burning.” The word “inflammable” pre-dates “flammable.” The word “inflammable” comes from the Latin word inflammāre, where the in- prefix means “to do” (like indoctrinate) rather than “not” (as in ineligible). But, few people study Latin, so people have been confused about what “inflammable” means pretty much since English became a language. In the 1920s, the National Fire Protection Association proposed “flammable” as a replacement for “inflammable.” The new word caught on, but the old word hasn’t been entirely replaced.

Which Word to Use

Flammable Symbol
This is the international symbol for flammable materials. No matter what word is used (flammable or inflammable), this symbol means the item is combustible.

Use the word “flammable” for easy-to-ignite materials. Use “combustible” for materials that can burn, but don’t easily ignite. Use “nonflammable” for flame retardant or noncombustible substances. While the term “inflammable” is a valid word, its meaning isn’t clear to everyone. Conveying whether or not something catches fire is important, so you don’t want to be misunderstood! If you can’t remember which word to use, go with the international symbol.

Examples of Flammable Materials

Here are examples of flammable or inflammable materials:

  • Gasoline
  • Kerosene
  • Propane
  • Methane
  • Ethanol
  • Coal
  • Acetone
  • Magnesium metal
  • Toluene

Dry wood and cotton are combustible, but not exactly flammable. They burn, but the materials don’t have a high vapor pressure, so they don’t easy catch fire.

Examples of Nonflammable Materials

Remember, if you apply enough energy even water and iron can burn. Nonflammable materials are just much harder to ignite. Here are examples of nonflammable materials:

  • Brick
  • Concrete
  • Stone
  • Glass
  • Water
  • Steel
  • Carbon dioxide
  • Nitrogen
  • Argon gas
  • Helium gas
  • Asbestos
  • Oxygen

Oxygen is not flammable. However, it’s an oxidizer that causes flammable substances to ignite and burn more readily. Therefore, oxygen should not be stored near flammable materials.

References

  • Garner, Bryan A. (2009). Garner’s Modern American Usage (3rd ed.). New York: Oxford UP.
  • O’Conner, Patricia T.; Kellerman, Stewart (2010). Origins of the Specious: Myths and Misconceptions of the English Language. Random House.
  • Oxford English Dictionary (2nd ed.). (2009). “Inflammable”.

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