What Is NFPA 704 or the Fire Diamond?

This is an example of a NFPA 704 warning sign.
This is an example of a NFPA 704 warning sign. The four colored quadrants of the sign indicate the types of hazards presented by a material. This is the NFPA 704 for sodium borohydride. public domain

You probably have seen NFPA 704 or the fire diamond on chemical containers. The National Fire Protection Association (NFPA) in the United States uses a standard called NFPA 704 as a chemical hazard label. NFPA 704 sometimes is called a "fire diamond" because the diamond-shaped sign indicates flammability of a substance and also communicates essential information about how emergency response teams should deal with a material if there is a spill, fire or other accident.

Understanding the Fire Diamond

There are four colored sections on the diamond. Each section is labeled with a number from 0-4 to indicate the level of hazard. On this scale, 0 indicates "no hazard" while 4 means "severe hazard". The red section indicates flammability. The blue section indicates a health risk. Yellow indicates reactivity or explosivity. The white is section is used to describe any special hazards.

Hazard Symbols on NFPA 704

Symbol and Number Meaning Example
Blue - 0 Does not pose a health hazard. No precautions are necessary. water
Blue - 1 Exposure may cause irritation and minor residual injury. acetone
Blue - 2 Intense or continued non-chronic exposure may result in incapacitation or residual injury. ethyl ether
Blue - 3 Brief exposure may cause serious temporary or moderate residual injury. chlorine gas
Blue - 4 Very brief exposure may cause death or major residual injury. sarin, carbon monoxide
Red - 0 Will not burn. carbon dioxide
Red - 1 Must be heated in order to ignite. Flashpoint exceeds 90°C or 200°F mineral oil
Red - 2 Moderate heat or relatively high ambient temperature is required for ignition. Flashpoint between 38°C or 100°F and 93°C or 200°F diesel fuel
Red - 3 Liquids or solids that readily ignite at most ambient temperature conditions. Liquids have a flash point below 23°C (73°F) and the boiling point at or above 38°C (100°F) or flash point between 23°C (73°F) and 38°C (100°F) gasoline
Red - 4 Rapidly or completely vaporizes at normal temperature and pressure or readily disperses in air and readily burns. Flashpoint below 23°C (73°F) hydrogen, propane
Yellow - 0 Normally stable even when exposed to fire; not reactive with water. helium
Yellow - 1 Normally stable, but may become unstable elevated temperature and pressure. propene
Yellow - 2 Changes violently at elevated temperature and pressure or reacts violently with water or forms explosive mixtures with water. sodium, phosphorus
Yellow - 3 May detonate or undergo explosive decomposition under the action of a strong initiator or reacts explosively with water or detonates under severe shock. ammonium nitrate, chlorine trifluoride
Yellow - 4 Readily undergoes explosive decomposition or detonates at normal temperature and pressure. TNT, nitroglycerine
White - OX oxidizer hydrogen peroxide, ammonium nitrate
White - W Reacts with water in a dangerous or unusual way. sulfuric acid, sodium
White - SA simple asphyxiant gas Only: nitrogen, helium, neon, argon, krypton, xenon