What are the two widely used types of continuous-loop systems?

The two widely used types of continuous-loop fire detection systems are indeed Kidde and Fenwal. These systems are designed to provide constant monitoring for potential fire hazards in various environments, particularly in powerplants and aviation applications.

Kidde systems typically utilize a wire that senses temperature changes, while Fenwal systems employ a thermal sensing cable that reacts to heat, allowing for precise and reliable detection of fires. Both types are engineered to activate alarms and potentially fire suppression systems automatically, ensuring rapid response to fire incidents.

In contrast, the other options do not represent types of continuous-loop systems. Thermal and optical refer to sensing technologies, but they do not specifically identify solutions that operate on a continuous-loop basis in fire detection. Pneumatic and fixed are terms associated with different mechanisms of fire detection and suppression but do not imply continuous-loop systems specifically. Lastly, gas and flame are too general to classify as continuous-loop fire detection systems; they describe detection methods rather than system types.

Thus, recognizing Kidde and Fenwal as the two prominent choices reflects an understanding of specialized technologies used for continuous monitoring in fire detection.