Which component reacts to temperature changes?

• A. Water Closet
• B. Sprinkler Positioning
• C. Listed or Labeled
• D. Thermal Element

Answer: (D)

The component that reacts to temperature changes is the thermal element. Each sprinkler head includes a temperature-sensitive device that holds the mechanism closed until heat reaches its rated threshold. In a glass-bulb sprinkler, heat causes the liquid inside the bulb to expand until the bulb shatters, releasing the sprinkler. In other types, a fusible link or pellet melts at the specified temperature, freeing the mechanism to release water. This temperature-responsive element is what actually triggers sprinkler activation. The other items—Water Closet, Sprinkler Positioning, and Listed or Labeled—are not temperature-sensitive components; they relate to bathroom fixtures, installation placement, and compliance labeling, respectively.