What happens when there is a resistance drop in the thermistor material of a Kidde system?

In a Kidde fire detection and extinguishment system, thermistors are temperature-sensitive resistive devices that change their resistance based on the temperature of the environment. When a significant change in temperature occurs, particularly in the context of a fire, the thermistor's resistance drops. This drop in resistance is critical for the system's operation.

A decrease in resistance typically indicates a rise in temperature, triggering the system to activate an alarm. The alarm serves as an initial warning to alert personnel of potential fire conditions. The activation of the alarm is essential for ensuring a prompt response to a possible fire, providing time to take necessary safety measures.

This behavior is a fundamental part of the design of such fire detection systems. Other outcomes, such as releasing the fire extinguishing agent or powering down the system, do not happen directly due to a resistance drop. The ground connection severing would be an unrelated failure mode that does not typically result from a normal operational change in the thermistor's performance.