What are the three categories rated in the NEPA 704 system?

• A. Health, Flammability, Instability
• B. Toxicity, Reactivity, Odor
• C. Color, Size, Weight
• D. Pressure, Temperature, Humidity

Answer: (A)

NFPA 704 uses three numeric ratings to convey the immediate hazards of a material: Health, Flammability, and Instability (also called Reactivity). Each of these is shown as a blue, red, or yellow section with a number from 0 to 4, where higher numbers mean greater hazard. The white diamond is reserved for special hazards, but it’s separate from these three ratings. So the three categories that are actually rated are Health, Flammability, and Instability. The other options mix in qualities that aren’t part of this system, like Odor or Toxicity, or refer to physical properties (Color, Size, Weight; Pressure, Temperature, Humidity) that aren’t the NFPA 704 categories.