Name the four NFPA 704 hazard codes and what the colors roughly indicate.

• A. Blue indicates health hazard, red indicates flammability, yellow indicates reactivity, white indicates special hazards
• B. Blue indicates humidity, red indicates weight, yellow indicates temperature, white indicates nothing
• C. The codes are used only for storage rooms and have no field use
• D. There are more than four codes and colors vary by manufacturer

Answer: (B)

NFPA 704 uses a four‑section diamond to convey hazards quickly. The four codes correspond to Health, Flammability, Reactivity, and Special Hazards. Each section is a color: blue for health, red for flammability, yellow for reactivity, and white for special hazards. In each colored field you’ll see a number from 0 to 4, where 0 means no hazard and 4 means a severe hazard. The white area may also show letters or symbols (for example, OX for oxidizers or W with a line through it for water reactivity) to flag specific hazards. The other options don’t fit NFPA 704 because humidity, weight, temperature, or “nothing” aren’t part of the standard, and the system uses four standardized categories with fixed colors.