A yellow placard signifies which hazard on hazmat?

• A. Flammability hazard.
• B. Health hazard.
• C. Reactivity hazard.
• D. Environmental hazard.

Answer: (C)

The main idea is how hazard information is color-coded for quick understanding. A yellow panel signals a reactivity hazard in the NFPA 704 system. This relates to how stable the material is and how it might react under certain conditions. Materials with reactivity hazards can become unstable or violently react when exposed to heat, shock, friction, or when mixed with water or other chemicals, and they may release energy or toxic gases or even detonate under the right conditions. The numbers inside the yellow section (0 to 4) indicate how severe that reactivity risk is, with higher numbers meaning greater danger.

This is different from the blue area, which indicates health hazards, and the red area, which indicates flammability hazards. The white area covers special hazards. Environmental hazard concerns aren’t conveyed by the yellow reactivity color on NFPA 704; those are typically shown with other labeling or pictograms.