What do the colors on an NFPA 704 marker represent?

• A. Red: Flammability; Blue: Health hazard; Yellow: Instability; White: Special considerations
• B. Red: Health hazard; Blue: Flammability; Yellow: Instability; White: Fire resistance
• C. Red: Instability; Blue: Flammability; Yellow: Health hazard; White: Special considerations
• D. Red: Fire resistance; Blue: Noise level; Yellow: Air quality; White: Occupancy

Answer: (A)

NFPA 704 uses a color-coded diamond to communicate hazards at a glance. Each color represents a different hazard category: blue indicates health hazard, red indicates flammability, yellow indicates instability (reactivity), and white is reserved for special hazards or notes.

The correct mapping is blue for health, red for flammability, yellow for instability, and white for special considerations. The numbers inside the colored sections (0–4) show how severe each hazard is, with higher numbers meaning greater danger. The white area may also include symbols (like W for water reactivity or OX for oxidizers) to convey specific, nonstandard hazards.

Other color assignments would misrepresent the risks—for example, making red about fire resistance or yellow about health would confuse responders and slow or endanger their actions. The white area is not about fire resistance or occupancy; it’s specifically for special hazards.