NFPA 704 Fire Diamonds
The NFPA 704 diamond shows health, flammability, instability, and special hazards for emergency response.
The NFPA 704 diamond, sometimes called the fire diamond, is a US standard marking that gives emergency responders a quick read of the hazards of materials in a building, tank, or storage area. It is posted on doors, walls, and tanks rather than on individual containers.
Each of the four colored sections carries a rating. Blue is health, red is flammability, and yellow is instability, each rated from 0 (minimal hazard) to 4 (severe hazard). The white section at the bottom carries special-hazard codes, such as W with a line through it for materials that react with water, OX for oxidisers, and SA for simple asphyxiant gases.
Ratings depend on the material and its properties. Do not copy GHS category numbers into the diamond.
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NFPA 704 and other hazard systems
NFPA 704 is a consensus standard published by the National Fire Protection Association. Local fire codes and authorities having jurisdiction decide where it is required. It is not a substitute for GHS labels or safety data sheets, which address workers handling the product.
The scales run in opposite directions. NFPA 4 is the most severe rating, while GHS category 1 is the most severe category. OSHA guidance is explicit that the hazard categories on a safety data sheet must not be copied into an NFPA diamond; ratings are assigned from the NFPA criteria.
Frequently asked questions
What do the four colors of the NFPA diamond mean?
Blue on the left is health hazard, red at the top is flammability, yellow on the right is instability (reactivity), and white at the bottom is for special hazards such as water reactivity (W with a line through it), oxidisers (OX), or simple asphyxiants (SA).
Is 4 or 0 the most dangerous NFPA rating?
4 is the most severe and 0 the least. This is the opposite of GHS, where category 1 is the most severe, which is a common source of mistakes.
Who decides the NFPA ratings for a chemical?
Ratings are assigned using the criteria in NFPA 704 and the properties of the actual material, such as its flash point and toxicity. Manufacturers often provide them on the safety data sheet, but the facility is responsible for the signs it posts, and the local fire authority may set requirements.