Final answer:
The question pertains to the types of devices used to trip preaction valves in fire protection systems. Alongside fixed temperature and rate-of-rise devices, the third type is manual devices.
Step-by-step explanation:
The student's question refers to the various types of initiating devices used to activate preaction sprinkler systems, which are typically used in fire protection. A preaction valve is an automated valve that controls the water supply to the sprinkler piping, held closed by air pressure and opened by the operation of a detection system before water is released into the sprinkler piping.
Three common types of devices used to trip (activate) preaction valves include fixed temperature devices, rate-of-rise devices, and manual devices. Fixed temperature devices operate when the ambient temperature reaches a predetermined point, melting a link or triggering a chemical reaction to release the valve. Rate-of-rise devices detect a rapid temperature increase, indicative of a fire, which expands air inside a sensor to trigger the sprinkler system. The third type, manual devices, require human intervention, such as a pull station, where an individual activates the fire suppression system manually.
In summary, a complete fire protection system utilizing a preaction valve might incorporate all these devices to ensure robust detection and response to various fire conditions. However, the choice of which devices to use and how to integrate them depends on specific building requirements, local codes, and the desired level of protection.