S95 Fire Alarm System Operation 3 — Questions and Answers
Question 1: When a fire alarm control unit receives a ground fault indication, the supervisor should FIRST:
- Immediately evacuate the building as a precautionary measure
- Silence the trouble signal and document the condition for later service
- Notify the authority having jurisdiction (AHJ) and arrange for prompt repair (Correct answer)
- Reset the control unit to clear the indication from the display
Correct answer: Notify the authority having jurisdiction (AHJ) and arrange for prompt repair
A ground fault is a trouble condition that must be reported to the AHJ and corrected promptly, as it can impair system reliability.
Question 2: Rate-of-rise heat detectors respond to which fire condition?
- Absolute temperature exceeding a fixed threshold only
- A rapid increase in temperature over a short time period (Correct answer)
- Visible combustion particles entering the sensing chamber
- Infrared radiation emitted by open flame
Correct answer: A rapid increase in temperature over a short time period
Rate-of-rise detectors activate when temperature increases at a rate exceeding approximately 12–15°F per minute, regardless of the actual temperature reached.
Question 3: A fire alarm system with a 'positive alarm sequence' (PAS) feature allows:
- The system to automatically reset after 3 minutes if no second device activates
- Trained personnel up to 3 minutes to investigate before general evacuation signals sound (Correct answer)
- The AHJ to remotely silence alarms from the supervising station
- Automatic escalation to a mass notification system after 60 seconds
Correct answer: Trained personnel up to 3 minutes to investigate before general evacuation signals sound
Under NFPA 72, PAS gives trained staff up to 3 minutes (180 seconds) to acknowledge and investigate before general notification is initiated.
Question 4: An addressable fire alarm system differs from a conventional system in that it:
- Uses wireless radio frequency devices instead of wired circuits
- Can identify the specific device in alarm or trouble by its unique address (Correct answer)
- Does not require a central control unit to operate
- Is limited to residential and small commercial occupancies
Correct answer: Can identify the specific device in alarm or trouble by its unique address
Addressable systems assign each device a unique identifier, allowing the control panel to pinpoint exactly which device is reporting an alarm or fault.
Question 5: Which of the following is the CORRECT action when a fire alarm system is taken out of service for maintenance exceeding four hours?
- Post a sign at the main entrance indicating the system is offline
- Provide a fire watch and notify the AHJ and supervising station (Correct answer)
- Disable only the affected zone and keep the rest of the system active
- Document the outage in the log book and resume normal operations
Correct answer: Provide a fire watch and notify the AHJ and supervising station
NFPA 72 and most fire codes require a fire watch when a fire alarm system is impaired, along with notification to the AHJ and supervising station.
Question 6: What does a 'trouble' signal on a fire alarm control unit indicate?
- An alarm condition has been detected and suppressed by staff
- A fault in the system wiring, power supply, or component that requires service (Correct answer)
- A supervisory condition in a sprinkler valve or water flow device
- The panel is conducting its scheduled automatic self-test
Correct answer: A fault in the system wiring, power supply, or component that requires service
A trouble signal indicates the system has detected an abnormal condition such as a wiring fault, ground fault, or component failure that requires service.
Question 7: In the context of fire alarm systems, what is the function of an 'End-of-Line' (EOL) resistor?
- It boosts signal strength over long wiring runs
- It allows the control panel to supervise the circuit for open or short faults (Correct answer)
- It limits current to protect initiating devices from power surges
- It terminates optical fiber cables used in addressable systems
Correct answer: It allows the control panel to supervise the circuit for open or short faults
An EOL resistor placed at the end of a Class B circuit allows the FACU to continuously monitor the loop for opens or shorts by measuring circuit impedance.
S95 Fire Alarm System Operation 3
When a fire alarm control unit receives a ground fault indication, the supervisor should FIRST: