In 1957 the National Fire Prevention Association (NFPA) began work on a standard system for identifying the hazards of materials aimed at helping emergency responders respond properly to fires, chemical spills, and other emergencies involving hazardous materials. Using background data collected by the Sectional Committee on Classification, Labeling and Properties of Flammable Liquids of the NFPA Committee on Flammable Liquids since 1952, the NFPA began compiling the standard. The system for the Identification of the Hazards of Materials for Emergency Response was adopted as a guide in 1961 and became an NFPA standard in 1990. The NFPA “hazard diamond” or “fire diamond” represents the Hazard Identification ratings system in an easy to understand visual way. This system identifies the hazards of a given material and the special equipment and procedures necessary to safely contain and clean up the material in an emergency. The diamond addresses the flammability, health, instability, and other hazards offered by short-term exposures occurring due to an emergency such as a fire or chemical spill. The NFPA Hazard Identification rating system represented by the diamond was developed for commercial, industrial and institutional locations that manufacture, store, process, or use hazardous materials. Emergency personnel use the diamond to assess potential risks, engineers and other safety workers use the diamond to evaluate workplace hazards and plan for emergency situations and clean-up of hazardous material. The NFPA diamond is not meant to be used by the general public, in the transportation of hazardous materials, or to rate the chronic or habitual occupational exposure to hazardous materials.

The NFPA chemical hazards diamond comprises four sections: the red section denotes flammability, the blue signifies health considerations, the yellow designates reactivity, and the white gives other special precautions. Each section of the diamond contains a number from 0 (minimal hazard) to 4 (severe hazard) that indicates the relative degree of risk presented by the material.

The red section indicates flammability, or the susceptibility of a material to burning.

  • A “0” rating indicates a non-combustible material, or a material that will not burn, such as water.
  • A “1” rating indicates that a material must be pre-heated before it will ignite. The flash point or the lowest temperature at which a liquid produces sufficient vapor to form an ignitable mixture with air near the liquid’s surface, of a liquid rated “1” is over 93° C/200° F.
  • A “2” rating indicates that the material must be heated or exposed to relatively high ambient temperature before it will ignite. The flash point of a liquid rated “2” is between 38° C/100° F and 93° C/200° F.
  • A material rated “3” is a liquid or solid that can ignite regardless of ambient temperature. The flash point of a liquid or solid rated “3” is between 23° C/73° F and 38° C/100° F.
  • A material rated “4” is a material that will vaporize at normal temperatures and atmospheric pressure or that will readily disperse in air and burn easily. The flash point of a material rated “4” is below 23° C/73° F

The blue section conveys information on health hazards to people exposed to the material.

  • A “0” rating indicates no hazard other than that of a combustible material, such as peanut or vegetable oil.
  • A “1” rating indicates potential irritation or minor injury if not treated.
  • A “2” indicates temporary incapacity or potential injury. Exposure requires medical treatment.
  • A “3” rating indicates that serious temporary or residual injury may occur even with medical treatment.
  • A material rated “4” may cause death or major residual injury even with medical treatment.

The yellow section indicates chemical reactivity or stability.

  • A material rated “0” is normally stable even when exposed to fire and does not react with water.
  • A material rated “1” is normally stable but becomes unstable at high temperature and pressure and will react with water.
  • A material rated “2” is normally unstable, will explode when mixed with water, or will undergo violent chemical reactions under elevated temperature and pressure, but will not detonate.
  • A material rated “3” may detonate or explode when exposed to an initiating force or when heated, and reacts explosively with water.
  • A material rated “4” detonates or explodes readily at normal temperature and pressure.

The white section indicates required protective equipment and other special considerations. The NFPA stipulates two symbols for this section.

  • “OX” denotes materials with oxidizing properties. These materials may decompose to yield oxygen and may cause fire when exposed to combustible materials.
  • “W” denotes materials that react with water.

Look to the following resources for more information:

  • NFPA 704: Frequently asked questions from the NFPA on standard 704 and the hazard diamond.