What Do the Chemical Diamond Signs Mean?

NFPA 704 Panel diagram.

Fire Diamonds – NFPA Signs

We all have seen these diamond signs with colors and numbers on them, but what are they? Commonly known as “fire diamonds,” they are concise, coded signs showing the danger of what chemicals are in a room or container. The National Fire Protection Association, or NFPA, designed these signs as warning labels. The first image shows what the colors and numbers mean, but below is a text version of it.

Red Diamond – Fire Hazard
  • 0 = Will not burn
  • 1 = Above 200°F (93°C)
  • 2 = Below 200°F (93°C)
  • 3 = Below 100°F (38°C)
  • 4 = Below 73°F (23°C)
Blue Diamond – Health Hazard
  • 0 = No hazard
  • 1 = Slightly hazardous
  • 2 = Hazardous
  • 3 = Extremely hazardous
  • 4 = Deadly
Yellow Diamond – Reactivity
  • 0 = Stable
  • 1 = Unstable if heated
  • 2 = Violent chemical
  • 3 = Shock or heat may detonate
  • 4 = May detonate
White Diamond – Specific Hazard
  • OXY = Oxidizer
  • ACID
  • ALK = Alkali
  • COR = Corrosive
  • Other symbols are listed below
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