What does the yellow color on the NFPA 704 Diamond signify?

The yellow color on the NFPA 704 Diamond specifically indicates a reactivity hazard. This system utilizes a color-coded diamond shape to quickly convey the hazards associated with materials, primarily in emergency situations. The yellow section, being in the upper part of the diamond, reflects the potential for a material to undergo chemical reactions that may release energy, which could be dangerous under certain conditions, such as if mixed with water or subjected to heat.

Understanding the reactivity hazard is crucial for first responders and personnel dealing with hazardous materials, as it informs them about the potential chemical hazards associated with a substance, including the likelihood of explosions or the release of toxic gases when the material is unstable or reactive under certain conditions. In contrast, the other colors represent different types of hazards—blue for health hazards, red for flammability, and white, which is used to indicate specific hazards like radiation or corrosivity.