NFSC Sub-Officer Entrance flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Fire Tetrahedron

Four elements sustain flaming combustion: fuel, oxygen, heat and the uninhibited chain reaction. Removing any one element extinguishes the fire.

Flash Point

The lowest temperature at which a liquid releases enough vapour to ignite momentarily when a flame is applied. It indicates fire risk, not the temperature of sustained burning.

Flashover

The sudden transition when hot compartment gases ignite all combustible contents at once, typically at gas temperatures of about 500–600°C.

Backdraught

An explosive ignition of unburnt fuel gases when air enters an oxygen-starved compartment. Warning signs include pulsing smoke and smoke-stained windows.

Heat Release Rate

The rate at which a fire releases energy, in kilowatts. It equals mass loss rate times effective heat of combustion times combustion efficiency.

Latent Heat of Vaporisation

The energy needed to turn a liquid into vapour without changing temperature. Water absorbs about 2.26 MJ per kilogram, making it an effective cooling agent.

Span of Control

The number of people or sectors one commander can effectively supervise, normally three to seven, with five as the practical ideal.

Offensive Firefighting

An interior attack on the fire with a known entry and exit route, adequate water supply and a viable rescue plan for occupants.

Mayday Transmission

The distress call for a firefighter in danger. It states name, location, situation and needed resources, and radio silence is maintained for it.

NPSH

Net positive suction head. Cavitation occurs when available NPSH falls below that required by the pump; reduce lift or speed to correct it.

Nozzle Reaction

The backward force produced by a flowing nozzle. It increases with flow and pressure and must be controlled on ladders and aerial platforms.

Foam Proportioning

Mixing concentrate with water: 3% for hydrocarbon fuels and 6% for polar solvents using alcohol-resistant foam. An aspirating branch expands the solution.

BA Cylinder Duration

Working duration equals cylinder volume times pressure divided by consumption rate, minus a safety margin of at least 25 percent.

Type IV Construction

Heavy timber construction with solid or laminated wood columns and beams of large cross-section, giving slow charring and moderate fire resistance.

Spalling

The breaking away of concrete or masonry surface under fire or water impact, exposing reinforcement and reducing structural load capacity.

Dead Load

The permanent weight of the structure itself, including walls, floors and roofing. It is distinct from live loads from occupants and contents.

Fire Door Requirements

Fire doors must be self-closing and latched, with hold-open devices that release on alarm. Gaps must not be wedged open.

Hot Work Permit

A control for welding, cutting and grinding: remove combustibles, post a fire watch, and inspect the area for at least 60 minutes after work ends.

Sprinkler Design Density

The water application rate in millimetres per minute over a stated operating area. Density times area gives the design flow.

BLEVE

Boiling liquid expanding vapour explosion. A pressurised container fails catastrophically when heated; cool it from cover and never approach tank ends.

Water-Reactive Material

A substance that liberates flammable gas or heat on contact with water. Use dry powder or inert gas, never water, to control it.

LPG Behaviour

Liquefied petroleum gas is heavier than air and pools in low areas, drains and basements. Natural gas and hydrogen are lighter and rise.

Vehicle Extrication Order

Stabilise the vehicle, disconnect the battery, manage glass, displace doors, remove the roof, and roll the dash in that sequence.

Confined Space Testing

Before entry, test for oxygen (19.5–23.5%), flammable gas (below 10% LEL) and toxic gas within limits. A permit and standby person are required.

Water Rescue Sequence

Reach, throw, row, go. A rescuer entering the water needs a flotation device and a shore tether, and it is the last option.

Pressure Conversion

One bar equals 100 kilopascals or about 14.5 pounds per square inch. One metre of water head equals about 0.098 bar.

Flow Rate Equation

Flow rate equals cross-sectional area times velocity. For a 50 mm bore, area is π times 0.025 squared, about 0.00196 square metres.

Friction Loss Formula

Friction loss in bar is approximately k times flow squared times hose length, where k depends on hose diameter and flow is in hundreds of litres per minute.

Heat Transfer Modes

Conduction transfers heat through solid contact, convection through moving fluids, and radiation by electromagnetic waves proportional to absolute temperature to the fourth power.

Ideal Gas Law

Pressure times volume equals amount times the gas constant times absolute temperature. It explains pressure rise in sealed containers exposed to fire.

Active Voice

A sentence construction in which the subject performs the action, as in 'Close the valve'. It is preferred in operational orders and reports.

Syllogism Rule

A valid conclusion must follow from the premises alone and hold in every arrangement that satisfies them. Outside knowledge is never used.