The NFPA 704 hazard rating diamond communicates hazards using four categories. Which categories are included?

• A. Health, Flammability, Reactivity, Special hazards
• B. Health, Flammability, Toxicity, Stability
• C. Health, Temperature, Pressure, Humidity
• D. Flammability, Reactivity, Radioactivity, Special hazards

Answer: (A)

NFPA 704 diamond uses four dimensions to convey hazards so responders can quickly assess what they’re dealing with. The four categories are health, which indicates potential harm from exposure; flammability, showing how easily the material ignites; reactivity, reflecting stability and how the substance behaves under heat, shock, or conditions that could cause it to react; and special hazards in the white section, which flags particular concerns like oxidizers or water-reactive properties. This combination—health, flammability, reactivity, and special hazards—is why that answer is the best fit.

The other options mix terms that aren’t part of the standard four categories. Toxicity and stability aren’t separate NFPA 704 categories; temperature, pressure, and humidity aren’t used as ratings in this system; and radioactivity isn’t its own category, though it can be noted in the special hazards section if needed.