CT Fire Alarm key terms

The National Fire Alarm and Signaling Code, which sets minimum requirements for the design, installation, testing, inspection, and maintenance of fire detection and signaling systems. Local jurisdictions adopt it, often with amendments.

The National Electrical Code, which governs wiring methods, conductor sizing, overcurrent protection, and grounding for fire alarm circuits. Article 760 covers fire alarm systems specifically.

A system installed within one building or group of buildings under single ownership or control to detect fire and alert occupants and responders. It is the most common commercial system type.

A facility that receives and monitors signals from a protected premises system and dispatches or relays information. Types include central station, proprietary, remote, and auxiliary stations, each with different code obligations.

The organization or individual responsible for approving equipment, installations, and procedures. The AHJ enforces the adopted code, reviews plans, and witnesses acceptance testing before a system is approved for use.

An audible or visual output indicating a fire condition or other emergency requiring evacuation or response. It is distinct from supervisory and trouble signals in both sound and required response.

A signal indicating that a system component or condition is abnormal, such as a closed sprinkler valve or low water level. It requires attention but does not indicate an actual fire emergency.

An audible and visual indication that a circuit, component, or power supply has failed or degraded. It warns that the system may not perform as designed and requires prompt service response.

An initiating or notification circuit that leaves the control unit, connects devices, and returns to the control unit. An open in the wiring does not prevent operation of devices on the remaining path.

An initiating or notification circuit that runs from the control unit through devices and ends at the last device. A single open fault disables all devices beyond the break, so circuit integrity is lower than Class A.

The wiring path connecting automatic detectors and manual pull stations to the control unit. It carries alarm-initiating signals and is monitored for opens, shorts, and ground faults.

The circuit supplying power to horns, strobes, speakers, and other notification appliances. It is typically supervised and must deliver adequate voltage at the last appliance under worst-case loading.

The loss of voltage along a conductor caused by resistance and current flow. On notification circuits, excessive drop can leave the last appliance unable to operate within its listed voltage range.

The relationship stating that voltage equals current multiplied by resistance (V = I x R). It underlies circuit calculations for current draw, conductor resistance, and appliance voltage drop.

A circuit in which current flows through each component in sequence along one path. A break anywhere stops current, and total resistance is the sum of individual resistances.

A circuit in which components connect across common points so each has its own current path. Voltage is the same across branches, and total current is the sum of branch currents.

The backup source, usually sealed lead-acid batteries, that keeps the system operating when normal AC power fails. It must support standby and alarm loads for code-specified durations.

The process of sizing backup batteries by adding standby current over the required standby period plus alarm current over the required alarm period, then applying a derating and aging allowance.

A measure of battery capacity expressing how many amperes a battery can deliver for a stated number of hours before reaching its end voltage. It is used to size standby batteries.

An unintentional connection between an energized conductor and ground. Fire alarm systems must detect and annunciate ground faults as trouble conditions so wiring can be repaired before it affects operation.

A component that produces a signal in response to a fire or manual action, such as a smoke detector, heat detector, waterflow switch, or manual pull station. It connects to an initiating device circuit.

A device that senses smoke particles or related combustion products and sends an alarm signal. Common types include ionization, photoelectric, and air-sampling detectors, chosen by expected fire characteristics.

A smoke detector that uses a light source and sensor; smoke scattering or obscuring light triggers an alarm. It responds well to smoldering fires that produce larger visible particles.

A smoke detector that senses changes in an electrical current flowing through ionized air inside a chamber. It tends to respond faster to flaming fires with small particles.

A device that responds to a fixed temperature threshold, a rapid rate of temperature rise, or both. It is used where smoke detection is unsuitable, such as kitchens or dusty areas.

A detector installed in HVAC ductwork to sense smoke moving through the air handling system. It typically shuts down fans and dampers and is supervised for airflow and housing placement.

A manually operated initiating device that lets an occupant trigger an alarm. It must be mounted at accessible heights along exit paths and is often the most reliable human-initiated alarm source.

A system in which each initiating or notification device has a unique address, letting the control unit identify the exact device in alarm or trouble. It simplifies troubleshooting and speeds response.

A system where devices share a zone circuit, and the control unit reports only the zone rather than the individual device. It is simpler and less costly but offers less diagnostic detail.

A defined area or group of devices reported together by the control unit. Zones help responders locate an alarm or trouble quickly and are often tied to building floors or compartments.

A device that alerts occupants, such as a horn, strobe, chime, speaker, or combination unit. Appliances must meet audibility and visibility requirements for the spaces they serve.

The coordinated flashing of strobes so they flash in unison rather than randomly. Synchronized flashes prevent seizure risk and meet code requirements when multiple appliances share a visible notification area.

A measure of luminous intensity for a strobe. Higher candela values are required for larger rooms or where mounting height and distance reduce effective visibility to occupants.

The degree to which an alarm sound can be heard above ambient noise. Codes set minimum sound pressure levels above average ambient, with higher levels required in sleeping areas.

A resistor installed at the far end of a supervised conventional circuit. It provides a known normal current so the control unit can detect opens and shorts as trouble conditions.

Continuous monitoring of wiring integrity so opens, shorts, and grounds are reported as trouble signals. Supervision ensures faults are found before an actual fire event occurs.

A documented test performed after installation to verify the system operates as designed and meets code. It is witnessed by the AHJ and must cover initiating devices, notification appliances, and power supplies.

Scheduled activities that verify a fire alarm system remains functional over time. NFPA 72 sets frequencies for testing devices, batteries, and circuits, and requires records of results.

A remote display panel that shows alarm, supervisory, and trouble conditions by zone or device. It helps responders and staff locate events without returning to the main control unit.