Chemical Storage Codes

Chemical storage codes are designed to make the public aware of hazards associated with chemicals being stored. The NFPA 704 diamond displays chemical storage codes in an easy-to-read format. Below are details of chemical storage codes, but first are chemical groups. Chemical groups should be stored separately from one another. The groups are: Metals, Acids, Bases, Oxidizers, Flammables, Poisons, Explosives, Reactives, Cyanides and Sulfides, and Low Hazards. Note: According to chemical storage codes, Ammonium Nitrate is considered an oxidizer, but should be stored separately from all other chemicals.

Chemical storage should be accompanied by chemical storage codes using an NFPA warning sign. This warning sign displays the hazards associated with the chemical storage using chemical storage codes that include colors, numbers, and symbols. Below we describe the meanings of these signs:

Chemical Storage Codes

Chemical Storage Codes - U.S. Chemical Storage


  • Will not burn under typical fire conditions.
  • 1  Does not burn readily; requires extensive preheating before ignition and combustion can occur.
  • 2 Must be moderately heated or exposed to high temperatures before ignition occurs. May release hazardous vapors when exposed to flame.
  • 3 Liquids and solids that can be ignited under almost all ambient temperature conditions.
  • 4 Burns readily, at atmospheric pressure and normal temperatures. Vaporizes at atmospheric pressure; vapors may be toxic.
    • Includes cryogenic material, and any liquid or gaseous material which is a liquid under pressure and has a flash point below 73°F and a boiling point below 100° (Class IA) including Ethyl Ether and Pentane.


  • 0  No health hazard.
  • May cause significant irritation.
  • 2  Exposure may cause temporary incapacitation.
  • 3  May cause serious or permanent injury, even with short exposure.
  • 4  Short exposure may cause death or major injury.


  • 0  Normally stable, even under fire conditions. Not water-reactive.
  • 1  Normally stable; can become unstable under pressure and high temperatures.
  • 2  Reacts violently with water. High temperatures result in violent chemical change.
  • May explode but requires a strong initiating source. Must be heated under confinement before initiation. Reacts explosively with water.
  • Readily capable of detonation or explosive decomposition at normal temperatures and pressures.


  • OX   Oxidizer – contributes to the combustion of another material.
  • W   Reacts violently or explosively with water.
  • SA  Asphyxiant gas.

Other Common Symbols

  • ACID  Material is acidic
  • ALK  Material is a base
  • COR  Material is corrosive

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