Describe the operation of a Lindberg fire detection system.

• A. Liquid-filled bulb expands triggers reed switch.
• B. Optical fiber along tube detects smoke.
• C. Gas detector uses catalytic reaction.
• D. Stainless steel tube contains inert gas and a discrete material that absorbs gas; heat releases gas increasing pressure, activating a pressure switch.

Answer: (D)

Lindberg fire detection works by using a sealed metal tube that contains inert gas and a material that releases gas when heated. When a fire heats the tube, the discrete material releases the stored gas, causing the pressure inside the tube to rise. That pressure movement actuates a pressure switch, which sends an electrical signal to indicate a fire condition. This is a heat-activated, pressure-change detector, designed to respond directly to elevated temperatures rather than to smoke or gas concentrations.

This differs from a liquid-filled bulb that expands to operate a reed switch, which is a different type of thermal detector; it also isn’t an optical fiber smoke detector, which senses smoke by light interaction, nor a catalytic gas detector, which responds to combustible gases rather than heat.