CFPS key terms

The sudden transition in a compartment fire when exposed combustible surfaces ignite almost simultaneously because radiant heat from the hot upper gas layer has driven them to ignition temperature. It marks the change from a growth-limited fire to a fully developed, ventilation-controlled fire.

A rapid deflagration that occurs when air enters a hot, fuel-rich, oxygen-starved compartment and mixes with accumulated unburned gases that then ignite, often forcing flame out of the opening with explosive force.

A model of combustion requiring four elements: fuel, oxidizer, heat, and an uninhibited chemical chain reaction. Removing any one element stops burning, and extinguishing agents work by interrupting at least one of them.

The thermal decomposition of a solid fuel into combustible gases and vapors before flaming combustion begins. It is an endothermic, temperature-driven chemical change, which is why solid fuels actually burn as gases.

The rate at which a fire liberates chemical energy, usually reported in kilowatts or Btu per second as it changes over time. It drives fire growth, detector response, and sprinkler activation.

The range of fuel concentration in air, expressed in volume percent, within which a gas or vapor will ignite. Below the lower limit the mixture is too lean; above the upper limit it is too rich.

A hypothetical fire, described by its growth rate, peak heat release rate, and duration, that an engineer selects to test whether a proposed design meets its stated performance criteria.

The organization or individual with legal authority to enforce a code and approve equipment, plans, and installations, such as a fire marshal or building official. It also settles questions of code interpretation.

A consensus document written by a standards organization for possible adoption by a government. Until a jurisdiction formally adopts it, a model code has no legal force.

A document cited by number and edition inside a code, making its provisions enforceable as part of that code. Compliance therefore depends on using the specific edition that was referenced.

Certification by a recognized testing laboratory that a product complies with a published standard and performs as described. Listed products bear a registered mark and are usually required for fire protection equipment.

Grouping of a building or space by its use and the hazard that use creates, such as assembly, business, or storage. The classification sets limits on height, construction type, and required egress features.

A design approach accepted on demonstrated ability to meet stated safety goals through engineering analysis of fire scenarios, rather than on strict compliance with fixed prescriptive rules.

The wiring pathway linking automatic detectors and manual pull stations to the fire alarm control unit. An open or short circuit on it normally produces a trouble indication at the panel.

The circuit that supplies operating power to audible and visible signaling appliances such as horns, speakers, and strobes. Its voltage drop and current must be calculated to ensure adequate output at the farthest device.

A fire alarm system in which each initiating device and appliance carries a unique address, letting the control unit report the specific device in alarm or trouble rather than only a circuit.

An indication that a system component is off-normal without being in alarm, such as a closed sprinkler control valve, low dry-pipe air pressure, or a fire pump left in manual mode.

The amount of water a sprinkler system must discharge over the design area, stated in gallons per minute per square foot. It is chosen from hazard-based tables and paired with an assumed operating area.

A coefficient describing a sprinkler's discharge, equal to flow in gallons per minute divided by the square root of pressure in psi. A larger K-value delivers more water at a given pressure.

The hydraulically most remote area of sprinkler coverage assumed to be flowing at once in a calculation, measured in square feet. Its size varies with hazard and may be reduced for quick-response sprinklers.

A sprinkler with a fast-acting thermal element that operates earlier in a growing fire than standard-response types, improving life safety and often allowing a smaller design area or reduced clearances.

A system with open sprinklers connected to a valve that opens on detection, discharging water from all heads simultaneously. It suits high-hazard occupancies needing rapid application over a large area.

A gaseous extinguishing medium that leaves no residue, does not conduct electricity, and is safe for occupied spaces at design concentration. Halocarbon and inert gas agents work by cooling and interrupting the combustion chemistry.

An alkaline solution, usually potassium-based, that reacts with hot cooking oil to form a smothering foam and also cools the fuel. It is the standard agent for Class K cooking equipment fires.

The number of people a space is designed to hold, computed from floor area and use or counted from fixed seating. It determines required egress width, number of exits, and exit capacity.

The continuous, unobstructed path from any point in a building to the public way, made up of exit access, the exit itself, and exit discharge.

The part of travel from a point in a space until two separate routes to exits become available. Codes limit its length because occupants have only one direction of escape during that segment.

The length measured along the natural path from the most remote point of a space to the nearest exit, limited by code according to occupancy and the presence of sprinkler protection.

A passage through a fire-rated wall with self-closing doors into an adjoining area or building that serves as a safe refuge, letting occupants leave the fire area without using stairs.

A protected space, such as a stair landing or rated room, where people unable to use stairs can wait for assistance. It must resist fire and smoke and connect to an accessible route.

A strategy in which occupants of a facility, typically a hospital or high-rise, stay inside protected compartments while staff control the fire, instead of evacuating the whole building.

The water rate in gallons per minute needed to control a fire in a given building, estimated from construction, occupancy, and exposure. It is compared against the supply available from mains and hydrants.

An empirical equation that predicts friction loss in a water-filled pipe from flow rate, pipe diameter, length, and a roughness coefficient. It is the workhorse of sprinkler and water main hydraulic calculations.

The pressure remaining at a point in a distribution system while water is flowing, typically measured at a hydrant during a flow test. Comparing it with static pressure shows how much supply is available.

The flow in gallons per minute at which a fire pump delivers its rated pressure at rated speed. Performance must also be verified at churn and at 150 percent of rated flow.

The lowest temperature at which a liquid produces enough vapor to form an ignitable mixture just above its surface, measured by a standard open-cup or closed-cup test. It drives flammable liquid classification.

A tank failure that occurs when a pressure vessel holding liquid above its atmospheric boiling point ruptures, releasing expanding vapor that can ignite into a fireball and throw vessel fragments.

A placard using a diamond with four color-coded fields for health, flammability, instability, and special hazards, each scored zero to four, warning responders about materials stored at a site.

Rapid combustion of finely divided combustible particles suspended in air inside an enclosure, producing pressure that can rupture structures and dislodge more dust, causing secondary explosions.

A structured process of identifying hazards, estimating how likely and how severe harm could be, and judging whether existing controls reduce risk enough to be acceptable.