In the NFPA hazard diamond, what does the number on the left side represent?

• A. Health
• B. Reactivity
• C. Flammability
• D. Special

Answer: (A)

The left-hand number on the NFPA 704 hazard diamond shows health hazard. It uses a blue quadrant with a 0–4 scale: 0 means no health hazard, 1 indicates slight hazard (minor irritation or exposure unlikely to cause harm), 2 signifies a hazardous level that could cause injury with normal exposure, 3 signals a severe hazard that could cause serious or permanent injury on short exposure, and 4 represents extreme danger where exposure could be fatal. This rating helps responders and workers quickly gauge how dangerous a chemical is to people and plan appropriate protection. The other sides convey different hazards: the top (red) for flammability, the bottom (yellow) for instability/reactivity, and the right (white) for special hazards such as oxidizers or water reactivity.