S95 Fire Alarm System Operation — Questions and Answers

Question 1: During a fire alarm signal, the control unit begins a pre-signal delay before notifying occupants. What is the primary purpose of this delay?

To allow time for automatic suppression systems to activate first
To permit trained personnel to investigate and confirm the alarm before general evacuation (Correct answer)
To give the fire department time to arrive on scene before occupants react
To reset the initiating device if it was triggered accidentally

Correct answer: To permit trained personnel to investigate and confirm the alarm before general evacuation

A pre-signal (or presignal) delay allows designated staff to investigate the alarm source before general notification, reducing unnecessary evacuations.

Question 2: A smoke detector in a corridor repeatedly goes into alarm during early morning hours with no visible smoke present. The MOST likely cause is:

Faulty wiring in the initiating device circuit
High humidity or condensation affecting the detector chamber (Correct answer)
The detector is programmed for nighttime sensitivity mode
Electromagnetic interference from HVAC startup

Correct answer: High humidity or condensation affecting the detector chamber

High humidity or condensation can cause ionization and photoelectric detectors to alarm nuisance-free by mimicking smoke particle density in the sensing chamber.

Question 3: According to NFPA 72, a single station smoke alarm differs from a system smoke detector primarily because it:

Uses a different sensing principle that is more accurate
Contains its own integral notification appliance and is self-contained (Correct answer)
Must be connected to a supervising station to be code-compliant
Is only permitted in residential occupancies of less than 500 sq ft

Correct answer: Contains its own integral notification appliance and is self-contained

A single station alarm integrates the detector and notification appliance in one unit, operating independently without a central control panel.

Question 4: A fire alarm control unit (FACU) is in the 'silenced' condition. Which of the following statements is TRUE?

The alarm signal has been acknowledged and all initiating devices have reset
Audible notification has been silenced but visual indicators and alarm condition remain active (Correct answer)
The system has been placed in a full reset and is ready for normal operation
Remote supervising station notification has been suspended until manual reset

Correct answer: Audible notification has been silenced but visual indicators and alarm condition remain active

Silencing only quiets audible appliances; the FACU remains in alarm condition with visual indicators active until the system is fully reset.

Question 5: Which component in a fire alarm system is responsible for converting a detected condition into an electrical signal sent to the control unit?

Notification appliance
Initiating device (Correct answer)
Signal line circuit
Annunciator panel

Correct answer: Initiating device

Initiating devices such as smoke detectors, heat detectors, and manual pull stations sense a condition and send a signal to the FACU.

Question 6: A fire alarm system supervisory signal is generated when:

A smoke detector enters alarm state
A sprinkler system valve is found in a partially closed position (Correct answer)
The control unit battery voltage drops below acceptable levels
A manual pull station is activated by a building occupant

Correct answer: A sprinkler system valve is found in a partially closed position

Supervisory signals indicate an off-normal condition in a fire protection system, such as a closed or partially closed sprinkler control valve.

Question 7: In a fire alarm system, Class B wiring differs from Class A wiring primarily in that Class B:

Uses fiber optic cable instead of copper conductors
Does not provide continuity of operation when a single open fault occurs (Correct answer)
Requires end-of-line devices at each initiating device
Is only approved for use with addressable control panels

Correct answer: Does not provide continuity of operation when a single open fault occurs

Class B circuits will lose communication to devices beyond a single open fault, whereas Class A circuits use a loop that maintains operation despite one open.

Question 8: 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 9: 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 10: 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 11: 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 12: 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 13: 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 14: 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.

Question 15: In a fire alarm system, the term 'alarm verification' refers to a feature that:

Requires a second manual pull station activation before sounding general alarm
Introduces a time delay to re-sample detector input before transmitting an alarm signal (Correct answer)
Sends an automatic test signal to the supervising station every 24 hours
Requires two independent smoke detectors to activate before initiating evacuation

Correct answer: Introduces a time delay to re-sample detector input before transmitting an alarm signal

Alarm verification temporarily clears the initiating device input and re-evaluates it to reduce nuisance alarms caused by transient conditions.

Question 16: Which type of occupancy is MOST likely to require a voice evacuation system rather than audible tone-only notification?

Single-family residential dwellings
High-rise buildings above 75 feet in height (Correct answer)
Small retail stores under 5,000 square feet
Open parking structures with fewer than 500 spaces

Correct answer: High-rise buildings above 75 feet in height

High-rise buildings typically require voice/alarm communication systems (VACS) to provide specific evacuation instructions to occupants on each floor.

Question 17: A photoelectric smoke detector operates on which principle?

Ionization of air molecules between two electrically charged plates
Interruption or scattering of a light beam by smoke particles (Correct answer)
Detection of infrared radiation emitted by combustion gases
Measurement of heat energy released per unit area of the sensing chamber

Correct answer: Interruption or scattering of a light beam by smoke particles

Photoelectric detectors use a light source and sensor; smoke particles scatter light onto the sensor, triggering an alarm.

Question 18: A supervisory signal from a sprinkler system pressure switch would MOST likely indicate:

A sprinkler head has activated and water is flowing
Air or water pressure in the system has deviated from normal operating range (Correct answer)
The sprinkler system's main drain valve has been fully opened
Smoke has been detected in the sprinkler riser room

Correct answer: Air or water pressure in the system has deviated from normal operating range

A pressure supervisory switch monitors system pressure and signals an off-normal condition when pressure falls outside acceptable limits, indicating a potential leak or tampering.

Question 19: When performing a fire alarm system inspection, the supervisor notices a smoke detector has a painted-over grille. The CORRECT action is to:

Test the detector with canned smoke to verify it still functions through the paint
Tag the detector as failed and replace it, since paint compromises sensing chamber entry (Correct answer)
Document the finding and schedule repainting of the surrounding ceiling to match
Clean the detector grille with compressed air to restore airflow

Correct answer: Tag the detector as failed and replace it, since paint compromises sensing chamber entry

Paint over a detector grille blocks airflow into the sensing chamber, rendering the detector non-functional; it must be replaced.

Question 20: A fire alarm control unit displays a 'common alarm' condition. This means:

Multiple supervisory signals are active simultaneously throughout the building
At least one initiating device in the system has activated an alarm condition (Correct answer)
The notification appliances are sounding on all zones including non-alarmed areas
The primary and secondary power supplies have both failed

Correct answer: At least one initiating device in the system has activated an alarm condition

A 'common alarm' LED or indicator on the FACU simply signals that one or more initiating devices are in an alarm state.

Question 21: Under NFPA 72, how often must a fire alarm system's battery backup be load-tested to verify adequate capacity?

Monthly using the panel's built-in self-test
Annually under simulated load conditions (Correct answer)
Every 3 years with a full discharge test
Every 5 years or when the battery reaches 80% of its rated life

Correct answer: Annually under simulated load conditions

NFPA 72 requires annual load testing of sealed lead-acid batteries to verify they can supply required standby and alarm loads under actual discharge conditions.

S95 Fire Alarm System Operation

During a fire alarm signal, the control unit begins a pre-signal delay before notifying occupants.
What is the primary purpose of this delay?

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