NFPA 704 Diamonds

What do they mean?

The National Fire Protection Association has developed a standard system for identifying chemical hazards. It consists of a diamond with four fields indicating hazards on a 1-4 scale for health, flammability and reactivity and a special field for unique hazards. You may encounter these symbols and numbers in the laboratory environment.

Health - Blue

  • 4.  Very short exposure could cause death or major residual injury.
  • 3.  Short exposure could cause serious temporary or moderate residual injury.
  • 2.  Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury.
  • 1.  Exposure would cause irritation with only minor residual injury).
  • 0.  Poses no health hazard, no precautions necessary.

Fire - Red

  • 4.  Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23°C (73°F).
  • 3.  Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point below 38°C (100°F) but above 23°C (73°F).
  • 2.  Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38°C (100°F) and 93°C (200°F).
  • 1.  Must be pre-heated before ignition can occur. Flash point over 93°C (200°F).
  • 0.  Will not burn.

Reactivity - Yellow

  • 4.  Readily capable of detonation or explosive decomposition at normal temperatures and pressures
  • 3.  Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked
  • 2.  Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water
  • 1.  Normally stable, but can become unstable at elevated temperatures and pressures
  • 0.  Normally stable, even under fire exposure conditions, and is not reactive with water

White - Special

  • W - reacts with water in an unusual or dangerous manner
  • OX or OXY - Oxidizer
  • COR- Corrosive; strong acid or base
    • ACID and ALK are more specific
  • BIO - Biological hazard
  • POI - Poisonous
  • . - is radioactive
  • CRY or CRYO - Cryogenic
*Note: W and OX are the only approved symbols in the NFPA 704 standard, however the above listed additional symbols are sometimes used in an unofficial manner.
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