The 0 to 4 range on the NFPA hazard diamond represents

• A. The hazard ratings used for health, flammability, and reactivity
• B. The temperature range of flammability
• C. The pH range of substances
• D. The classification of oxidizers

Answer: (A)

NFPA 704 uses a blue, red, and yellow diamond where each colored quadrant is numbered from 0 to 4 to indicate how hazardous a substance is in that aspect: health (blue), flammability (red), and reactivity (yellow). A 0 means no hazard in that category, while a 4 means a severe hazard. This quick numeric scale lets responders gauge risk at a glance and decide on protective measures and procedures. The white section holds special hazard information (like OX for oxidizers or W with a slash for water reactivity) and is not part of the 0–4 numeric rating. Temperature range, pH range, or a separate oxidizer classification aren’t conveyed by these numbers.