Glossary of Terms


Authority Having Jurisdiction
An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure. 

Automatic Sprinkler System
A sprinkler system of pipes with water under pressure that allows water to be discharged immediately when a sprinkler head operates.

Automatic Standpipe System
A standpipe system that is attached to a water supply capable of supplying the system demand at all times and that requires no action other than opening a hose valve to provide water at hose connections.


Clean Agent
Electrically nonconducting, volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation.

Combined Dry Pipe-Preaction System
A sprinkler system employing automatic sprinklers attached to a piping system containing air under pressure, with a supplemental detection system installed in the same areas as the sprinklers. Operation of the detection system actuates tripping devices that open dry pipe valves simultaneously and without loss of air pressure in the system. Operation of the detection system also opens listed air exhaust valves at the end of the feed main, which usually precedes the opening of sprinklers. The detection system also serves as an automatic fire alarm system.

The time period of plant testing and operation between initial operation and commercial operation.

One who contracts on predetermined terms to provide labor and materials and who is responsible for performance of a construction job in accordance with construction documents.

Control Valve
A valve employed to control (shut) a supply of water to a sprinkler system.

Corrosion Resistance
The ability of a material to withstand deterioration of its surface or its properties when exposed to its environment.


Deluge System
A water spray sprinkler system using open nozzles attached to a piping system that is connected to a water supply through a valve that is opened by means of a detection system installed in the same area as the sprinkler nozzles. When the valve opens, water flows into the piping system and discharges through all nozzles attached to the system.

Deluge Valve
A water supply control valve intended to be operated by actuation of an automatic detection system that is installed in the same area as the water spray nozzles. Each control valve also shall be capable of manual operation. 

Detection Devices
Electrical, pneumatic, thermal, mechanical, or optical sensing instruments, or subcomponents of such instruments, whose purpose is to cause an automatic action upon the occurrence of some preselected event.

Detection System
A system consisting of detectors; controls; control panels; automatic and manual actuating mechanisms; all wiring, piping, and tubing; and all associated equipment that is used to actuate an extinguishing system.

Dry Pipe Sprinkler System
A sprinkler system employing automatic sprinklers that are attached to a piping system containing air or nitrogen under pressure, the release of which (as from the opening of a sprinkler) permits the water pressure to open a valve known as a dry pipe valve, and the water then flows into the piping system and out the opened sprinklers.

Dry Standpipe System
A system that shall be arranged as follows: (1) includes devices to admit water to the system automatically by opening a hose valve; (2) admits water to the system through manual operation of remote control devices located at each hose station; (3) has no permanent water supply (a filled standpipe having a small water supply connection to keep the piping filled by requiring water to be pumped into the system shall be considered to be a dry standpipe).


Early Suppression Fast Response (ESFR) Sprinklers
A type of fast-response sprinkler listed for its capability to provide fire suppression of specific high-challenge fire hazards.


The entity performing off-site manufacture or assembly, or both, of construction components or systems.

Fire Hazards Analysis (FHA)
An analysis to evaluate potential fire hazards and appropriate fire protection systems and features to mitigate the effects of fire in any plant location.

Fire Protection Manager
The person directly responsible for the fire prevention and fire protection program at the plant.

Fire Suppression
The sharp reduction of the rate of heat release of a fire and the prevention of regrowth.

Fixed Fire Suppression System
A total flooding or local application system consisting of a fixed supply of extinguishing agent permanently connected for fixed agent distribution to fixed nozzles that are arranged to discharge an extinguishing agent into an enclosure (total flooding), directly onto a hazard (local application), or a combination of both; or an automatic sprinkler system.

A stable aggregation of small bubbles of lower density than oil or water that exhibits a tenacity for covering horizontal surfaces.

Foam System
A system provided on fire apparatus for the delivery of a proportioned foam and water mixture for use in fire extinguishment. The system includes a concentrate tank, a method for removing the concentrate from the tank, a foam-liquid proportioning system, and a method (e.g., hand lines or fixed turret nozzles) of delivering the proportioned foam to the fire.

Any material that will maintain combustion under specified environmental conditions.


Grounding System
A system of conductors that provides a low-impedance return path for leakage and fault currents.


The potential for harm or damage to people, property, or the environment. Hazards include the characteristics of facilities, equipment systems, property, hardware, or other objects, and the actions and inactions of people that create such hazards.


The striking of a protected surface by water droplets issuing directly from a water spray nozzle.

Indicating Valve
A valve that has components that show if the valve is open or closed. Examples are outside screw and yoke (OS&Y) gate valves and underground gate valves with indicator posts.

A mechanical or electrical device that shows when an extinguishing system or a critical component of it is ready to operate, or if it has already operated.

A visual examination of a system or portion thereof to verify that it appears to be in operating condition and is free of physical damage.

Inspection Testing and Maintenance Services
A service program provided by a qualified contractor or qualified owner's representative in which all components unique to the property's systems are inspected and tested at the required times and necessary maintenance is provided. This program includes logging and retention of relevant records.

That place at which independent systems meet and act on or communicate with each other.

Internal Excess-Flow Valve
An excess-flow valve constructed and installed so that damage to valve parts exterior to the container does not prevent closing of the valve.

Ionization Smoke Detection
The principle of using a small amount of radioactive material to ionize the air between two differentially charged electrodes to sense the presence of smoke particles. Smoke particles entering the ionization volume decrease the conductance of the air by reducing ion mobility. The reduced conductance signal is processed and used to convey an alarm condition when it meets preset criteria.


Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or service meets appropriate designated standards or has been tested and found suitable for a specified purpose.

Looped Sprinkler System
A sprinkler system in which multiple cross mains are tied together so as to provide more than one path for water to flow to an operating sprinkler and branch lines are not tied together.


Work, including, but not limited to, repair, replacement, and service, performed to ensure that equipment operates properly.

Minimum Water Supply
The quantity of water required for fire control.

A dispersion of fine liquid droplets in a gaseous medium.

Action that moderates the severity of a fire hazard or risk.


Normally Occupied
An enclosure where, under normal circumstances, persons are present.

The time at which an alarm is received and acknowledged at a communications center.

Notification Appliance
A fire alarm system component such as a bell, horn, speaker, light, or text display that provides audible, tactile, or visible outputs, or any combination thereof.

A constricting appliance attached to the end of a fire hose or monitor to increase the water velocity and form a stream.

Nozzle Pressure
Pressure required at the inlet of a nozzle to produce the desired water discharge characteristics. 

Nuisance Alarm
Any alarm caused by mechanical failure, malfunction, improper installation, or lack of proper maintenance, or any alarm activated by a cause that cannot be determined.


Obstructed Construction
Panel construction and other construction where beams, trusses, or other members impede heat flow or water distribution in a manner that materially affects the ability of sprinklers to control or suppress a fire.

The Occupational Safety and Health Administration of the U.S. Department of Labor.

The organization(s) with fiscal responsibility for the operation, maintenance, and profitability of a plant.


Piping System
All piping, valves, and fittings from the outlet of the point of delivery from the supplier to the outlets of the equipment shutoff valves.

A graphic representation of a building structure or portion of a building structure, fire protection system, or fire assembly or equipment.

Point of Origin
The exact physical location where a heat source and a fuel come in contact with each other and a fire begins.

Postulated Fire
A fire that is assumed to occur in a specific area of a nuclear plant.

Preaction Sprinkler System
A sprinkler system employing automatic sprinklers that are attached to a piping system that contains air that might or might not be under pressure, with a supplemental detection system installed in the same areas as the sprinklers.

Fabricated prior to erection or installation on or in a building or on a foundation.

Pressure Relief Device
A device that is designed to open in order to prevent a rise of internal fluid pressure in excess of a specified value due to emergency or abnormal conditions and that can be of the reclosing or other type, such as one having a rupture disk or fusible plug that requires replacement after each use.

Pressure Test
An operation performed to verify the gastight integrity of gas piping following its installation or modification.

Pressure-Regulating Device
A device designed for the purpose of reducing, regulating, controlling, or restricting water pressure. Examples include pressure-reducing valves, pressure control valves, and pressure-restricting devices.

Preventive Maintenance
The act or work of keeping something in proper condition by performing necessary preventive actions, in a routine manner, to prevent failure or breakdown.

Protective Systems, Equipment, or Apparatus
Automatic sprinklers, standpipes, carbon dioxide systems, clean agent systems, automatic covers, and other devices used for extinguishing fires.

A mechanical device that transfers or raises, or transfers and raises the pressure of a fluid (water).


Quality Assurance Program
A predefined set of periodic observations, tests, and other procedures that provide an independent record to the owner, authority having jurisdiction, and RDP that the construction is in general conformance with the approved design documents.

Quality Control
The operational procedures provided by contractors to ensure compliance with construction documents.


Rated Capacity
The flow available from a device, at the designated residual pressure either measured or calculated.

The application of more than one device or system, or part of a device or system, with the objective of ensuring that in the event of one failing to perform its function another is available to perform that function.

The redevelopment of a fire after it was thought to have been extinguished by the original fire service response.

The probability that the system, structure, or component of interest will function without failure for a given interval of time or number of cycles. For standby systems, structures, or components, this includes the probability of success upon demand.

Relief Valve
A device that allows the bypass of fluids to limit the pressure in a system.

As applied to vehicles and facilities, to furnish with new parts or equipment to constitute a deliberate modification of the original design (as contrasted with an overhaul or a replacement in kind).

The vertical pipes connecting the system main line(s) with the branch lines on the various levels of the facility.

The set of probabilities and consequences for all possible accident scenarios associated with a given plant or process.


A guard or protective device used as a safety measure to protect persons from a present or impending hazard.

Semiautomatic Standpipe System
A standpipe system that is attached to a water supply capable of supplying the system demand at all times and that requires activation of a control device to provide water at hose connections.

Service Testing
The regular, periodic inspection and testing of apparatus and equipment, according to an established schedule and procedure, to ensure that they are in safe and functional operating condition.

Shutoff Valve
A valve designed so that, when closed, it completely stops the flow.

A status indication communicated by electrical or other means.

Signaling Line Circuit
A circuit or path between any combination of circuit interfaces, control units, or transmitters over which multiple system input signals or output signals, or both, are carried.

Signaling Line Circuit Interface
A system component that connects a signaling line circuit to any combination of initiating devices, initiating device circuits, notification appliances, notification appliance circuits, system control outputs, and other signaling line circuits.

Single Station Alarm
A detector comprising an assembly that incorporates a sensor, control components, and an alarm notification appliance in one unit operated from a power source either located in the unit or obtained at the point of installation.

Refers to the contiguous property that makes up a nuclear power plant facility. This would include areas both inside the protected area and the owner-controlled property.

Smoke Detector
A device that detects visible or invisible particles of combustion.

Sprinkler System
For fire protection purposes, an integrated system of underground and overhead piping designed in accordance with fire protection engineering standards. The installation includes one or more automatic water supplies. The portion of the sprinkler system aboveground is a network of specially sized or hydraulically designed piping installed in a building, structure, or area, generally overhead, and to which sprinklers are attached in a systematic pattern. The system is usually activated by heat from a fire and discharges water over the fire area.

Standpipe System
An arrangement of piping, valves, hose connections, and allied equipment with the hose connections located in such a manner that water can be discharged in streams or spray patterns through attached hose and nozzles, for the purpose of extinguishing a fire and so protecting designated buildings, structures or property in addition to providing occupant protection as required.

Structural Element
The columns and girders, beams, trusses, joists, braced frames, moment-resistant frames, and vertical and lateral resisting elements, and other framing members that are designed to carry any portion of the dead or live load and lateral forces, that are essential to the stability of the building or structure.

Supervisory Signal
A signal indicating the need for action in connection with the supervision of guard tours, the fire suppression systems or equipment, or the maintenance features of related systems.

System Actuation Valve
The main valve that controls the flow of water into the water spray system.


An individual qualified and authorized by the compliant product manufacturer to provide specified care and maintenance to the product, and perform inspection, repair, and testing beyond the level classified as "user repair." 


A device by which the flow of liquid, air or other gas, loose material in bulk, or other such material can be started, stopped, or regulated by a movable part that opens or obstructs passage.

An opening for the passage of, or dissipation of, fluids, such as gases, fumes, smoke, and the like.


Water Mist System
A distribution system connected to a water supply or water and atomizing media supplies that is equipped with one or more nozzles capable of delivering water mist intended to control, suppress, or extinguish fires and that has been demonstrated to meet the performance requirements of its listing and this standard.

Water Spray System
An automatic or manually actuated fixed pipe system connected to a water supply and equipped with water spray nozzles designed to provide a specific water discharge and distribution over the protected surfaces or area.

Water Supply
A source of water that provides the flows (L/min) and pressures (bar) required by the water-based fire protection system.

Water Tank
A tank supplying water for water-based fire protection systems.

Wet Pipe Sprinkler System
A sprinkler system employing automatic sprinklers attached to a piping system containing water and connected to a water supply so that water discharges immediately from sprinklers opened by heat from a fire.

Wet Pipe Water Mist System
A water mist system using automatic nozzles attached to a piping system containing water and connected to a water supply so that water discharges immediately from nozzles operated by the heat from a fire.

Wet Standpipe
A standpipe system having piping containing water at all times.

Wireless Control Panel
A component that transmits/receives and processes wireless signals.
Definitions provided by the 2005 NFPA Glossary of Terms


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