AHJ (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.
Alarm Valve – Opens the stop valve when the fire sprinkler system activates, controlling the flow of water into the fire sprinkler system.
Alarm Test Valve – Allows you to test your fire sprinkler system at shut off connections.
Antifreeze Sprinkler System – Wet pipe fire sprinkler system that holds a small amount of antifreeze in the pipes to keep the water from freezing. When the sprinkler system activates, some of the antifreeze is discharged along with the water.
Automatic Sprinkler System – Fire suppression system that operates automatically in response to the heat from flames. When activated, the fire sprinkler system douses the area in its effect radius with water.
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.
Code – A body of law systematically arranged to define requirements pertaining to the safety of the general public from fire and other calamities.
Control Valve – A valve employed to control (shut) a supply of water to a sprinkler system, or a portion of the sprinkler system.
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.
Dry Pipe Fire Sprinkler System – Automatic fire sprinkler system that stores water in a central tank as opposed to in the pipes. Slightly increases sprinkler response time, and is useful in areas where water stored in pipes can freeze.
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).
Fire Pump – Pump that supplies the fire sprinkler system with water.
Fire Pump Controller – Group of devices that govern the starting and stopping of the fire pump driver as well as monitoring and signaling the status and condition of the pump.
Flow Switch – Monitors the flow of water through different sections of pipe within the automatic fire sprinkler system. If the flow switch senses enough water flowing, they trigger the alarm.
FM 200 Fire Suppression System – Clean Agent fire suppression system with no effect on the ozone layer. Used as a replacement for Halon 1301.
Hazard – A condition of element that provides a source of ignition for a hostile fire or that contributes to the spread and severity of a hostile fire.
Hostile Fire – Any unwanted or destructive fire.
Hydraulically Designed System – Calculated sprinkler system where pipe sizes are selected based on pressure loss to prescribe water density in gallons/minute/sq. ft.
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.
Inspection – 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.
Maintenance – Work, including, but not limited to, repair, replacement, and service, performed to ensure that equipment operates properly.
Pipe Schedule System – Sprinkler system in which pipe sizing is selected from a schedule determined by the occupancy of a building in which a given number of sprinklers are allowed to be supplied from specific pipe sizes.
Pressure Gauge – Measures the pressure within the fire sprinkler system. 
Pressure Switch – Enables the fire sprinkler system to alert the fire department that your fire sprinkler system is going off, monitors your fire alarm system by watching for a fall in water pressure after the alarm valve.
Sprinkler Head – A sprayer made up of a threaded nipple connecting the head to a water pipe, an activation device such as a fusible link or heat sensitive bulb held in place by a yolk and a deflector that breaks up the water spray into fine droplets.
Sprinkler System – Grid of water pipes and sprinkler heads installed in a building to control and extinguish fires.
UL – Underwriters Laboratories, a certification authority for many appliances and systems associated with fire protection.
Wall Hydrant – A hydrant mounted on the outside wall of a building that is fed from interior piping and equipped with control valves located inside the building. Wall hydrants are normally key operated and accessed via the building’s exterior.
Water Hammer – A sudden surge of pressure caused when fast moving water is abruptly blocked. This pressure can be as much as seven or more times more powerful than static pressure!
Wet Pipe Fire Sprinkler System – A standard fire sprinkler system, with water stored directly in the pipes held back by the fire sprinkler heads until a fire starts.
Wet Barrel Hydrant – Type of fire hydrant sometimes used where there is little to no danger of freezing weather. Each outlet of a wet barrel hydrant is outfitted with a valved outlet threaded for a fire hose.
Working Pressure – The maximum allowable pressure to which a sprinkler system, pipe or hose can be subjected to safely.