In the NFPA 704 hazard diamond, what do numbers 0–4 represent?

• A. Color code intensity.
• B. Container size.
• C. Severity level of hazard in that category; 0 means no hazard, 4 indicates extreme hazard.
• D. Weather conditions.

Answer: (C)

The numbers 0–4 indicate how severe the hazard is in each category of the NFPA 704 diamond. In each colored section—blue for health, red for flammability, and yellow for reactivity—the number shows the level of danger, with 0 meaning no hazard and 4 meaning extreme hazard. This quick scale lets responders assess risk at a glance and decide on appropriate protective measures and actions. It’s about how bad the hazard is in that aspect, not about how big the container is, nor about weather conditions, and the white section uses symbols for special hazards rather than numbers.