Which type of sprinkler head utilizes a plunger?

The type of sprinkler head that utilizes a plunger is the chemical pellet sprinkler head. This system typically employs a plunger mechanism where a small pellet containing a chemical composition is used to hold the valve in a closed position. When a fire occurs and the surrounding temperature rises, the heat activates the chemical pellet, causing it to burst. This action releases the plunger, allowing water to flow through the sprinkler head and extinguish the fire.

In contrast, other types of sprinkler heads operate on different principles. For example, bulb-type sprinkler heads contain a sealed glass bulb filled with a heat-sensitive liquid. When the temperature rises, the liquid expands, causing the bulb to shatter, which subsequently opens the sprinkler valve. Fusible link sprinkler heads, on the other hand, use a metal link that melts at a specific temperature, releasing the valve as well. Guarded heads are designed to prevent damage from physical impact or obstructions, but they do not utilize a plunger mechanism in their operation.

Thus, the unique functioning of the chemical pellet mechanism sets it apart from those alternatives, confirming its correct identification as the sprinkler head that uses a plunger.