Initiating Devices Flashcards

A sprinkler system waterflow switch is classified as what type of initiating device?

Answer: Alarm initiating device

Waterflow switches are alarm initiating devices because water flowing through a sprinkler pipe indicates a fire has activated a sprinkler head, requiring an alarm signal.

A waterflow switch on a wet-pipe sprinkler system typically has a built-in retard feature. What is the purpose of this retard?

Answer: To prevent false alarms caused by momentary pressure surges or water hammer

The retard chamber delays the alarm signal for 30–90 seconds to filter out brief pressure surges in the piping that would otherwise cause nuisance alarms.

A valve supervisory switch (tamper switch) on a control valve generates what type of signal at the fire alarm control panel?

Answer: Supervisory signal

A valve supervisory switch monitors the open or closed position of a sprinkler control valve and generates a supervisory signal when the valve is moved from its normal (fully open) position.

Which initiating device is specifically designed to detect the presence of flame rather than smoke or heat?

Answer: Infrared or ultraviolet flame detector

Infrared (IR) and ultraviolet (UV) flame detectors sense the specific radiation wavelengths emitted by flames, providing very fast response to open fires.

A duct smoke detector must be located how far downstream from air supply inlets or outlets, mixing dampers, or any obstructions per NFPA 72?

Answer: At least 3 duct widths

NFPA 72 requires duct smoke detectors to be installed at least 3 duct widths downstream from any obstruction or air inlet/outlet to ensure representative air sampling.

A fire alarm system supervisory signal is generated by a low air pressure switch on a dry-pipe sprinkler system when air pressure drops below the required level. What condition does this indicate?

Answer: The air compressor has failed or there is a significant air leak in the system

Low air pressure in a dry-pipe system indicates either a failed compressor or a significant leak; this triggers a supervisory signal because the system's ability to function is impaired.

A carbon monoxide (CO) detector used as an initiating device on a fire alarm system must comply with which standard for residential applications?

Answer: UL 2075

UL 2075 is the standard for gas and vapor detectors and sensors, which covers CO detectors intended for connection to fire alarm systems in residential and commercial applications.