NFPA placard yellow stands for which hazard?

• A. Flammability
• B. Instability/Reactivity
• C. Special Notice
• D. Health Hazard

Answer: (B)

The main idea here is how the NFPA 704 hazard diamond communicates different kinds of danger at a glance. The yellow section specifically represents instability or reactivity. That means the chemical’s tendency to undergo a chemical reaction—sometimes violently—under changes in temperature, pressure, or shock, or when mixed with other substances. In practice, a higher number in the yellow quadrant signals greater reactivity risk, from materials that may decompose or polymerize under certain conditions to those that can react violently or even detonate if heated, shocked, or combined with water or other chemicals. This is why responders look for the yellow marking to gauge potential reactive hazards and handle the substance with precautions to avoid initiating a dangerous reaction. The other colors denote different hazards: blue is health, red is flammability, and the white section covers special hazards such as oxidizers or water reactivity.