Which two types of Quick Operating Devices (Q.O.Ds) are commonly used?

Accelerators and exhausters are commonly used types of Quick Operating Devices (Q.O.Ds) in sprinkler systems because they facilitate rapid response to changes in system pressure and ensure that water flow is appropriately managed during a fire incident.

Accelerators are devices that increase the speed at which water is delivered to the sprinkler heads. They reduce the lag time in water flow, allowing for a quicker response in extinguishing a fire. This rapid activation is crucial in fire protection, where every second counts.

Exhausters are used to remove air from a system, which can also help improve the performance and responsiveness of the sprinkler system. By ensuring that the system is free of air pockets, exhausters contribute to a timely and effective water discharge during emergencies.

Other options presented do not accurately reflect the specific types of devices classified as Quick Operating Devices in the context of sprinkler systems. For instance, detectors and alarms are essential components but serve a different function in detecting fire and alerting occupants rather than directly influencing water delivery speed. Similarly, valves and sensors play roles in system control and monitoring but do not fit the precise definition of Quick Operating Devices.