What defines frangible-bulb sprinkler heads?

Frangible-bulb sprinkler heads are distinctly characterized by their use of a liquid-filled glass bulb that shatters when exposed to heat. This mechanism is crucial for the automatic operation of the sprinkler system. When a fire occurs, the temperature increases, causing the liquid inside the bulb to expand. Once it reaches a specific temperature threshold, the pressure from the expansion breaks the glass, allowing water to flow and extinguishing or controlling the spread of the fire.

This design ensures a quick response to the fire incident, as the sprinkler will activate only when necessary, reducing water damage and optimizing fire control. Understanding this system is essential for firefighters, as it impacts how they manage fire suppression systems and respond to emergencies effectively. Other options refer to different types of sprinkler mechanisms or features but do not accurately describe the mechanism at the heart of frangible-bulb sprinkler heads.