SCO Fire key terms

The sudden transition to full-room fire involvement, when heat radiated from the ceiling and hot gas layer ignites nearly all exposed combustible surfaces at once.

A violent ignition of accumulated unburned fuel gases that occurs when oxygen suddenly enters an oxygen-depleted, hot, smoke-filled compartment.

Chemical decomposition of a solid material driven by heat, releasing combustible gases before visible flame ever appears on the surface.

The four elements needed for flaming combustion: fuel, oxygen, heat, and the uninhibited chemical chain reaction that sustains the flame.

Stratification of fire gases in a compartment, with hot smoke collecting at the ceiling and cooler air remaining near the floor.

The horizontal boundary in a smoke-filled compartment separating the upper hot gas layer from the lower cooler, clearer air layer.

A fire involving flammable or combustible liquids, such as gasoline, oil, or solvents, where a smothering or foam blanket is usually required.

A fire in cooking oils or fats in commercial cooking equipment, requiring a wet chemical agent that saponifies the burning oil.

The lowest temperature at which a material will continue to burn on its own once an external ignition source is removed.

The upper or lower concentration of fuel vapor in air that will support combustion; outside this range the mixture is too lean or too rich to burn.

A device that senses combustion products such as visible smoke or aerosols and sends a signal to the fire alarm control unit.

A detector that monitors a limited area around its mounting location, as opposed to sampling air from a wide or extended space.

A detector installed in an HVAC duct that senses smoke moving through the air handling system and typically shuts down the unit.

A fire alarm architecture in which each initiating device has a unique identifier, letting the panel report the exact device in alarm.

A fire alarm arrangement where devices share a circuit or zone, so the panel reports only the zone rather than the individual device.

A device such as a horn, speaker, or strobe that alerts occupants of a fire alarm condition through audible or visible signals.

An emergency communication arrangement that delivers live or prerecorded spoken instructions to occupants instead of only a tone or horn.

An automatic sprinkler system with water held under pressure in the piping at all times, discharging immediately when a sprinkler operates.

A sprinkler system with pressurized air or nitrogen in the piping and water held back by a valve, used where freezing is a concern.

A sprinkler arrangement requiring a detector signal to admit water into the piping before a sprinkler head operates, limiting accidental discharge.

A heat-actuated discharge device that opens at a rated temperature, releasing water in a designed spray pattern over a protected area.

A numerical rating of a sprinkler's discharge coefficient that relates water flow to the square root of pressure at the head.

A gaseous extinguishing medium that leaves no residue and works mainly by interrupting the chemical chain reaction or by cooling.

A suppression system using CO2 to displace oxygen and cool the fire, hazardous to people because it is an asphyxiant in enclosed spaces.

A fixed system using an alkaline solution that reacts with burning cooking fats to form a smothering soap-like foam.

The continuous and unobstructed path of travel from any point in a building to a public way, comprising exit access, exit, and exit discharge.

The portion of the egress path that leads from an occupied space to the entrance of an exit, such as a corridor or aisle.

The part of the means of egress between the termination of an exit and a public way, such as an exterior walkway or courtyard.

The measured length of the egress route from the most remote point in a space to an exit, limited by code according to occupancy.

The distance a person must travel before reaching a point where two separate routes to exits become available.

A designated space protected from fire and smoke where people unable to use stairs can wait safely for assisted evacuation.

The calculated number of people a space is designed to hold, derived from floor area and occupancy-based density factors.

The period, in hours or minutes, that a building element withstands a standard fire test while maintaining its separating or structural function.

A fire-resistance-rated wall or assembly with protected openings that restricts fire spread and typically must remain continuous through concealed spaces.

A rated wall with a lower fire-resistance rating than a fire barrier, usually used to separate dwelling units or corridors within a building.

A written authorization issued before welding, cutting, or other spark-producing work, documenting fire watch, area preparation, and equipment checks.

A person assigned to patrol an area for fire conditions and provide early notification, often required when protection systems are impaired.

A condition in which a fire protection system or feature is out of service or degraded, requiring notification, mitigation, and often a fire watch.

A document assembled in advance describing a building's layout, hazards, access, utilities, and suppression resources to guide emergency operations.

A written or verbal statement of objectives, strategies, and tactics that guides responders for an operational period of an incident.