What does the W symbol on the NFPA hazard diamond indicate?

• A. Water reactive
• B. Water reactive hazard present water safety
• C. Wet conditions
• D. Warning

Answer: (A)

The symbol in the white special-hazards area signifies a water reactivity hazard. When a material carries the W, it means it can react with water—sometimes violently—releasing heat, hydrogen gas, or other hazardous products. Because of this, it must be kept away from water or moisture, and response and storage procedures should avoid water-based methods. In practice, handle with dry, non-aqueous precautions and follow specific guidance from the material’s safety data sheet for appropriate extinguishing agents and spill response. This is not about general warning or “wet conditions,” but a specific warning that the substance may react with water.