What does a frangible bulb do in a sprinkler head?

What does a frangible bulb do in a sprinkler head?

• A. It seals the sprinkler head until activation
• B. It vents air from the system
• C. It breaks as the pressure increases
• D. It changes color when heated

Answer: (C)

Frangible bulbs act as the temperature‑sensitive trigger inside a sprinkler head. They’re small glass bulbs filled with a liquid that expands when heated to the head’s rated activation temperature. As heat from a fire raises the temperature, the bulb breaks, releasing the seal and allowing water to flow through the head. This mechanism keeps the sprinkler from releasing water too soon and ensures activation occurs only when exposed to sufficient heat. It’s not about sealing or venting, and the bulb’s color is simply indicative of its rating, not a dynamic change during operation.

Frangible bulbs act as the temperature‑sensitive trigger inside a sprinkler head. They’re small glass bulbs filled with a liquid that expands when heated to the head’s rated activation temperature. As heat from a fire raises the temperature, the bulb breaks, releasing the seal and allowing water to flow through the head. This mechanism keeps the sprinkler from releasing water too soon and ensures activation occurs only when exposed to sufficient heat. It’s not about sealing or venting, and the bulb’s color is simply indicative of its rating, not a dynamic change during operation.