HKIE Professional Assessment - Fire Discipline key terms

The sudden transition from a growing compartment fire to full-room involvement, in which all combustible surfaces ignite almost simultaneously, driven by radiant feedback from the hot smoke layer to the fuel surfaces.

The horizontal boundary at an opening where the outflowing hot smoke layer meets the inflowing cool air, marking the pressure-equalisation level between the fire compartment and the adjacent space.

The buoyant accumulation of combustion products beneath a ceiling, whose depth, temperature and optical density govern visibility, tenability and the onset of flashover conditions.

A deflagration caused by air entering an under-ventilated compartment where fuel-rich gases have accumulated, which can produce a fireball and pressure wave when an opening is made.

An idealised fire described by heat release rate against time, with assumed growth, peak and decay phases, used as the input to fire engineering calculations and egress analysis.

The rate at which a fire releases thermal energy, usually expressed in kilowatts or megawatts; it is the single most influential parameter governing smoke production and tenability.

A growth model in which heat release rate rises with the square of time after ignition, characterised by a growth coefficient that classifies fires as slow, medium, fast or ultra-fast.

The condition in which occupants can survive and escape without incapacitation, assessed against limits for smoke optical density, temperature, radiant heat, and toxic gas concentrations.

A cumulative toxicity measure that sums the fractions of incapacitating dose received over time from asphyxiant and irritant gases, allowing comparison of exposure against escape time.

A qualitative and quantitative description of a fire event covering ignition location, fuel package, ventilation conditions and growth, adopted as a basis for design or assessment.

A mathematical representation of a fire in an enclosure, ranging from simple zone models with two layers to computational fluid dynamics, used to predict temperatures and smoke spread.

A fire model that divides a compartment into an upper hot layer and a lower cool layer, solving conservation equations for each to predict layer depth, temperature and species concentrations.

Numerical solution of the governing equations of fluid flow and heat transfer on a discretised domain, applied to fire engineering to predict smoke movement, temperatures and velocities in complex geometries.

The continuous route of protected travel from any point in a building to a place of safety in the open air, comprising exits, protected corridors, staircases and discharge points.

The measured length of the escape route from the furthest occupied point to the nearest exit or protected escape route, limited by code according to occupancy and fire risk.

An enclosed space with fire-resisting construction and self-closing doors that separates a staircase from the accommodation, preventing smoke entry and maintaining a tenable escape route.

Subdivision of a building by fire-resisting walls, floors and ceilings into fire compartments that limit fire and smoke spread, providing time for evacuation and firefighting operations.

The period, in minutes, for which a building element resists fire in terms of stability, integrity and insulation when tested to a standard time-temperature curve.

A seal of approved fire-resisting material installed where services or openings penetrate a fire-resisting element, restoring the integrity and insulation of that element.

An automatic fixed installation in which heat-sensitive heads open individually to discharge water onto a fire, controlled from a dedicated water supply and usually supervised by a control valve set.

The assumed rate of water application per unit area over the design area, used to size a sprinkler system for a given hazard classification and occupancy risk.

A vertical pipe installed in a building, kept permanently charged with water, providing firefighting water at hydrant outlets on each floor for use by the fire service.

A first-aid firefighting installation comprising a reel of small-bore hose connected to the water supply, intended for rapid use by occupants on incipient fires.

A dedicated pump that maintains pressure and flow in a fire service installation, typically arranged duty and standby with automatic starting and a dedicated suction tank.

An engineered arrangement of natural vents, mechanical fans, shafts or barriers that limits smoke spread and maintains clear escape or firefighting access routes.

A smoke control method that maintains a positive pressure in protected staircases or lobbies relative to the fire floor, preventing smoke infiltration when doors are closed.

The documented logic governing how detection, alarm, suppression and smoke control systems interact, including cause-and-effect matrices, zoning and fail-safe behaviour.

A tabular statement of the outputs required for each detected input, such as alarm, plant shutdown, damper closure or smoke vent activation, forming the basis for system testing.

A fixed installation discharging an inert or chemical agent to extinguish fire by oxygen displacement or chemical inhibition, used where water would damage protected assets.

A suppression installation producing fine water droplets that cool the fire, displace oxygen and attenuate radiant heat, using far less water than conventional sprinklers.

Hong Kong legislation requiring prescribed commercial premises and specified commercial buildings to provide or improve fire safety measures, including means of escape and fire service installations.

The primary Hong Kong statute controlling building design, construction and use, supported by regulations and codes of practice covering fire safety and means of escape.

A statutory notice issued under the Fire Safety (Buildings) Ordinance requiring the owner or occupier to carry out specified fire safety improvement works within a stated period.

Hong Kong guidance issued by the Buildings Department setting out deemed-to-satisfy provisions for escape routes, exit capacities, travel distances and protected escape design.

The systematic examination of a fire scene to determine origin, cause and development, using burn patterns, witness evidence and physical evidence while preserving chain of custody.

The location where a fire is determined to have started, established by correlating fire patterns, witness accounts, protected surfaces and the extent of damage.

Interpretation of charring, soot deposition, spalling and heat-line marks to reconstruct fire spread direction, ventilation effects and the region of greatest heat exposure.

The organised arrangements for maintaining fire safety in an occupied building, covering maintenance of installations, staff training, drills, records and periodic inspection.

Insurance protecting an engineer against claims of negligence or professional error, underpinning ethical responsibility for advice given on fire safety design and assessment.