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NFSC Sub-Officer Entrance study materials
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NFSC Sub-Officer Entrance practice questions

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Question 1Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

In the fire triangle, which component is removed when a carbon dioxide extinguisher is discharged onto a flaming liquid spill?

  1. Oxygen, because the gas displaces air at the fuel surface Correct answer.
  2. Heat, because the gas is colder than the fuel
  3. The chemical chain reaction, because CO2 is a catalyst
  4. Oxygen, because CO2 chemically binds free oxygen

Explanation

Carbon dioxide extinguishes mainly by smothering: the dense gas cloud displaces oxygen from around the burning surface, dropping the local oxygen concentration below the level needed for flaming combustion. Cooling and dilution of fuel vapour play minor secondary roles, but displacement of air is the dominant mechanism.

Question 2Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A compartment fire has passed flashover and all combustible contents are burning at once. Which description best characterises this phase?

  1. Fully developed, with high heat release and ventilation-controlled burning Correct answer.
  2. Incipient, with growth still limited to the item of origin
  3. Smouldering, with no visible flame and low temperature
  4. Decay, with heat release steadily falling to ambient

Explanation

After flashover the fire is fully developed: every exposed combustible surface is involved, heat release is at its peak, and burning rate becomes limited by the available ventilation openings. The incipient and smouldering phases precede this, and decay follows once fuel is consumed.

Question 3Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which class of fire involves combustible metals such as magnesium and sodium?

  1. Class D Correct answer.
  2. Class B
  3. Class A
  4. Class F

Explanation

Class D covers fires in combustible metals, which require special dry powders because water and foam can react violently with them. Class A is carbonaceous solids, Class B flammable liquids, and Class F cooking oils and fats.

Question 4Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Water is most effective as an extinguishing agent because of which dominant property?

  1. Its high latent heat of vaporisation, which absorbs large amounts of heat Correct answer.
  2. Its low density, which allows it to spread over liquids
  3. Its high viscosity, which coats fuel surfaces
  4. Its ability to chemically inhibit flame radicals

Explanation

Water absorbs heat mainly through its very high specific heat capacity and, more importantly, its high latent heat of vaporisation, converting to steam and cooling the fuel below its ignition temperature. The steam produced also dilutes oxygen, but cooling is the primary mechanism.

Question 5Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A dry powder extinguisher labelled for multiple classes extinguishes flame primarily by which mechanism?

  1. Cooling the fuel below its fire point
  2. Interrupting the chemical chain reaction of combustion Correct answer.
  3. Displacing all nitrogen from the compartment
  4. Forming a soapy film that seals the fuel surface

Explanation

Dry chemical powders work chiefly by chemical inhibition: the fine particles decompose in the flame and scavenge the free radicals that propagate combustion, breaking the chain reaction. Cooling and blanketing effects are secondary.

Question 6Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which type of sprinkler system keeps its pipes filled with air under pressure and only admits water when a sprinkler head operates?

  1. Dry pipe system Correct answer.
  2. Deluge system
  3. Wet pipe system
  4. Pre-action system

Explanation

A dry pipe system holds compressed air in the piping and uses a dry pipe valve that trips to admit water only after a sprinkler head fuses and releases pressure. This avoids water in unheated spaces where freezing would burst pipes.

Question 7Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which extinguishing medium is specifically designed to form a film over a burning liquid and prevent vapour release?

  1. Wet chemical
  2. Carbon dioxide
  3. Dry sand
  4. Aqueous film-forming foam Correct answer.

Explanation

Aqueous film-forming foam (AFFF) spreads a thin aqueous film ahead of the foam blanket over the fuel surface, sealing it and suppressing vapour release while also cooling. This makes it effective on Class B liquid fires.

Question 8Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

What is the primary purpose of a fire damper in a ventilation duct passing through a fire-resisting wall?

  1. To cool the duct surface below ignition temperature
  2. To prevent the spread of fire and smoke through the duct opening Correct answer.
  3. To detect heat and sound an alarm zone signal
  4. To boost air flow to dilute smoke in the duct

Explanation

A fire damper closes automatically when heat or smoke is detected, sealing the duct penetration so fire and smoke cannot travel through the wall opening into another compartment. It maintains the integrity of the fire-resisting separation.

Question 9Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A pool of petrol is burning in a bunded area. Applying a solid water jet directly onto the surface is dangerous mainly because:

  1. Water raises the flash point of petrol above ambient
  2. The water sinks below the fuel and the steam produced can eject burning liquid Correct answer.
  3. Water reacts chemically with petrol to produce flammable gas
  4. The jet cools the petrol below its pour point

Explanation

Petrol is less dense than water, so a water jet sinks beneath the fuel layer. The water flashes to steam, expands enormously, and can throw burning fuel out of the bund in a violent boil-over or slop-over effect, spreading the fire.

Question 10Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A compartment has limited ventilation and the fire becomes ventilation-controlled. What is the most likely consequence for firefighting crews?

  1. The fire becomes fuel-controlled and cools the compartment
  2. Flashover risk is eliminated because oxygen is low
  3. Unburnt fuel and smoke accumulate, and admitting air can cause rapid fire growth Correct answer.
  4. Heat release rate falls steadily and the fire self-extinguishes

Explanation

In a ventilation-controlled fire, the oxygen supply limits combustion, so unburnt fuel and flammable gases build up in the compartment. If a door or window is opened, fresh air can mix with these hot gases and cause sudden rapid growth or a backdraught.

Question 11Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which statement correctly distinguishes flashover from backdraught?

  1. Flashover happens in the decay phase; backdraught happens in the incipient phase
  2. Flashover occurs only in liquid fuel fires; backdraught occurs only in solid fuel fires
  3. Flashover is the simultaneous ignition of all combustible surfaces in a compartment; backdraught is the explosive ignition of accumulated gases when air enters Correct answer.
  4. Flashover is a sudden inflow of air into a hot compartment; backdraught is the ignition of all surfaces at once

Explanation

Flashover marks the transition to a fully developed fire, when radiant heat ignites all combustible surfaces almost simultaneously. Backdraught is a separate phenomenon in which hot, fuel-rich, oxygen-deficient gases ignite explosively when fresh air is admitted.

Question 12Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

For a liquid with a flash point of 12 degrees Celsius and a fire point of 18 degrees Celsius, what does the flash point indicate?

  1. The temperature at which the liquid will continue to burn once ignited
  2. The temperature at which the liquid will spontaneously ignite without an ignition source
  3. The temperature at which the liquid gives off enough vapour to ignite momentarily when a flame is applied Correct answer.
  4. The temperature at which the liquid becomes too viscous to flow

Explanation

The flash point is the lowest temperature at which a liquid releases sufficient vapour to form an ignitable mixture with air near its surface; the vapour flashes but sustained burning may not follow. The fire point is the higher temperature at which vapour is produced fast enough to sustain combustion.

Question 13Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Why is a wet chemical extinguisher preferred over a water extinguisher for a deep-fat fryer fire?

  1. It lowers the oil's auto-ignition temperature
  2. It cools the oil faster than water can
  3. It displaces all oxygen in the kitchen permanently
  4. It reacts with the oil to form a saponified foam blanket that seals the surface Correct answer.

Explanation

Wet chemical agents react with hot cooking oil to form a soap-like saponified layer that floats on the surface, sealing it and preventing vapour escape while also cooling. Water can cause violent spitting and spread burning oil.

Question 14Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

In a building fitted with a wet riser, what is the purpose of the landing valves?

  1. To automatically activate the sprinkler pump
  2. To vent air from the riser during filling
  3. To allow firefighting hose to be connected and water drawn at upper floors Correct answer.
  4. To drain the system after use

Explanation

A wet riser is a permanently charged vertical main with landing valves at each floor, letting firefighters connect hose and obtain water at height without running hose up stairways. The valves are outlets, not drains, vents, or pump controls.

Question 15Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A foam blanket applied to a burning alcohol fire breaks down quickly. Which foam type is most appropriate?

  1. High-expansion foam of any type
  2. Alcohol-resistant foam Correct answer.
  3. Protein foam
  4. Fluoroprotein foam

Explanation

Alcohols and other polar solvents destroy conventional protein and fluoroprotein foams. Alcohol-resistant foam contains a polymer membrane that protects the bubble structure from the solvent, so the blanket persists.

Question 16Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which principle explains why a closed compartment door slows fire growth in a corridor?

  1. The door increases the compartment's ventilation rate
  2. The door limits the supply of oxygen and restricts heat and smoke spread Correct answer.
  3. The door increases the fuel load of the compartment
  4. The door raises the auto-ignition temperature of the contents

Explanation

A closed fire door restricts air supply to the fire and blocks the passage of heat and smoke into the corridor, keeping the fire ventilation-controlled and protecting the escape route. This is the basis of compartmentation as a passive fire protection measure.

Question 17Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A carbon dioxide system protects a computer server room. What is the main reason CO2 is chosen here over water?

  1. CO2 leaves no residue and does not damage electrical equipment Correct answer.
  2. CO2 cools the room more effectively than water
  3. CO2 is safe for personnel to breathe in high concentrations
  4. CO2 is cheaper than water for all installations

Explanation

CO2 is a clean agent: it evaporates completely and leaves no residue, so sensitive electronics are not damaged, unlike water which causes short circuits and corrosion. However, it is an asphyxiant and requires evacuation and warning before discharge.

Question 18Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which condition must be met for a backdraught to occur when a compartment door is opened?

  1. The compartment contains only solid fuels with no gas production
  2. The compartment contains hot, fuel-rich gases with insufficient oxygen and a source of ignition Correct answer.
  3. The fire is in the incipient stage with abundant oxygen
  4. The compartment is cool and well ventilated

Explanation

A backdraught requires a hot, oxygen-deficient compartment in which incomplete combustion has generated large quantities of flammable gases. When air enters, the gases mix within the flammable range and ignite, producing a pressure wave.

Question 19Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A sprinkler head with a nominal operating temperature of 68 degrees Celsius is installed in a room whose ceiling reaches 50 degrees Celsius in summer. Why is this rating acceptable?

  1. The operating temperature must be safely above normal ceiling temperatures but low enough to respond to fire Correct answer.
  2. Sprinkler heads operate only on smoke detection, not temperature
  3. The rating only matters in winter when temperatures are low
  4. The head must operate at ambient temperature to ensure quick response

Explanation

Sprinkler bulbs or fusible links are rated to fuse well above expected ambient ceiling temperatures so they do not operate spuriously, yet low enough to respond promptly to a fire. A 68 degrees Celsius rating comfortably exceeds a 50 degrees Celsius summer ceiling.

Question 20Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which statement about the flammable range of a gas is correct?

  1. A gas with a wide flammable range is generally more hazardous because more concentrations can ignite Correct answer.
  2. Flammable limits are independent of temperature and pressure
  3. The lower flammable limit is the richest mixture that will burn
  4. The wider the flammable range, the narrower the band of concentrations that can ignite

Explanation

The flammable range lies between the lower and upper flammable limits. A wider range means a greater span of fuel-air concentrations can ignite, so the gas is generally more hazardous. Flammable limits shift with temperature and pressure.

Question 21Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A compartment fire is burning steadily with a heat release rate limited by the size of the ventilation opening. A crew opens a large window. What is the expected immediate effect?

  1. Heat release rate decreases because the fire is cooled by incoming air
  2. The fire enters the decay phase immediately
  3. The fire becomes fuel-controlled and burns more slowly
  4. Heat release rate increases as oxygen supply improves, potentially causing rapid fire growth Correct answer.

Explanation

In a ventilation-controlled fire, the burning rate is limited by oxygen. Opening a large vent admits air, allowing more fuel to burn and raising the heat release rate sharply, which can trigger rapid fire development or flashover.

Question 22Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which combination of conditions best explains why a high-expansion foam system is unsuitable for outdoor liquid fuel fires in windy conditions?

  1. High-expansion foam cannot cool any fuel surface
  2. Wind disrupts the fragile foam blanket, and high expansion ratios give low resistance to disruption Correct answer.
  3. High-expansion foam is too dense to spread over fuel
  4. High-expansion foam reacts chemically with hydrocarbons

Explanation

High-expansion foam has a high air-to-liquid ratio, producing a light, fragile blanket that wind can break up and displace, exposing the fuel. It is therefore suited to total flooding of enclosed spaces rather than exposed outdoor spills.

Question 23Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A sealed room contains a gas at a concentration above its upper flammable limit. A leak allows air to enter slowly. What hazard develops?

  1. The concentration passes down through the flammable range, creating an explosive mixture Correct answer.
  2. The mixture becomes too rich to burn permanently
  3. The upper flammable limit rises so ignition becomes impossible
  4. The gas condenses into a liquid and cannot ignite

Explanation

As air dilutes a mixture that started above the upper flammable limit, the fuel concentration falls. It must pass through the flammable range on its way down, so at some point the mixture becomes ignitable and an ignition source could cause an explosion.

Question 24Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A fire in a room with a single high-level opening is burning under ventilation control. Compared with a room with a low-level inlet and high-level outlet, what is the main difference in fire behaviour?

  1. The single high-level opening provides better inflow of fresh air at the fire base
  2. The single high-level opening eliminates the risk of backdraught
  3. There is no difference because ventilation openings act identically
  4. The single high-level opening gives poorer air supply to the seat of the fire, increasing incomplete combustion and smoke production Correct answer.

Explanation

Air entering at high level does not reach the base of the fire efficiently, so combustion is more incomplete and smoke and unburnt gases accumulate. A low inlet and high outlet arrangement sets up a better flow path, supplying air at the fire and venting hot gases.

Question 25Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which statement correctly describes the relationship between a material's auto-ignition temperature and its flash point?

  1. Auto-ignition temperature applies only to solids, while flash point applies only to liquids
  2. Auto-ignition temperature is the temperature at which ignition occurs without an external ignition source and is generally higher than the flash point Correct answer.
  3. Flash point and auto-ignition temperature are the same value for all liquids
  4. Auto-ignition temperature is always lower than the flash point

Explanation

The auto-ignition temperature is the temperature at which a material ignites spontaneously without a spark or flame, and for most flammable liquids it is considerably higher than the flash point. The flash point requires an external ignition source and marks the lowest temperature for ignitable vapour.

Question 26Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A fire tetrahedron is used to describe the four elements required for sustained flaming combustion. Which set lists those four elements?

  1. Fuel, oxygen, heat and a chemical chain reaction Correct answer.
  2. Fuel, oxygen, pressure and a chemical chain reaction
  3. Fuel, nitrogen, heat and an ignition source
  4. Fuel, oxygen, heat and smoke production

Explanation

The fire tetrahedron extends the older fire triangle by adding the chemical chain reaction to fuel, oxygen and heat. Removing any one of the four elements stops flaming combustion, which is the basis for classifying extinguishing agents by their mode of action.

Question 27Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which extinguishing mechanism is the primary way a clean-agent halocarbon such as an HFC blend extinguishes a flaming fire in an occupied room?

  1. Saponification of the burning liquid surface
  2. Cooling the fuel surface below its fire point
  3. Displacement of oxygen to below 8 per cent
  4. Chemical interruption of the combustion chain reaction Correct answer.

Explanation

Halocarbon clean agents act mainly by chemically interrupting the free-radical chain reaction in the flame, so they work at low design concentrations. They are specified for occupied spaces because they do not rely on reducing oxygen to a level that would be dangerous to people.

Question 28Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A dry riser is installed in a building. Which statement describes its normal condition and purpose?

  1. It is kept empty and is charged by a pumping appliance at the fire service inlet to supply landing valves. Correct answer.
  2. It is connected to the automatic sprinkler system and boosts pressure to the sprinkler heads.
  3. It contains foam concentrate that is proportioned at each landing valve.
  4. It is permanently charged with water and supplies hose reels on every floor.

Explanation

A dry riser is an empty vertical main with a fire service inlet at ground level and landing valves on upper floors. It is charged on arrival by a pumping appliance, which allows crews to obtain water at height without running hose up stairways.

Question 29Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which statement correctly describes the role of a fire-resisting compartment wall in limiting fire spread?

  1. It removes heat from the fire by absorbing it into the wall mass.
  2. It interrupts the fuel supply to the fire in the adjacent compartment.
  3. It restricts the spread of fire and hot gases between compartments for a stated fire resistance period. Correct answer.
  4. It lowers the oxygen concentration in the compartment of origin.

Explanation

Compartmentation divides a building so that a fire is contained within its compartment for a defined period, measured by the fire resistance of the separating elements. The wall does not extinguish the fire; it buys time for evacuation and firefighting.

Question 30Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A fire in a basement store is burning with a deep-seated glowing zone in a pile of cardboard. Which extinguishing agent application is most appropriate?

  1. A foam blanket laid over the top of the pile
  2. A dry powder burst aimed at the visible flames only
  3. A single brief application of carbon dioxide to the surface
  4. A sustained application of water with adequate penetration and cooling Correct answer.

Explanation

Deep-seated fires in class A materials need the cooling and penetration that water provides, applied long enough to reach the glowing material. Surface-acting agents may knock down flames while the interior continues to burn and can later reignite.

Question 31Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A pressure gauge on a stored-pressure water extinguisher reads in the green zone, but the extinguisher has not been serviced for several years. Which additional check is most important before the appliance is accepted for use?

  1. Checking whether the safety pin is painted over
  2. Weighing the cylinder to confirm the propellant charge
  3. Checking the service label and confirming the annual service and extended service dates Correct answer.
  4. Testing the hose by running water through it at full pressure

Explanation

A gauge only shows that the stored pressure is within range at that moment; it says nothing about internal condition or the agent. The service record confirms that the required annual servicing and extended service have been carried out.

Question 32Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A liquid with a flash point of 23 degrees Celsius is stored in an open container in a workshop at 30 degrees Celsius. What is the main fire hazard?

  1. The liquid cannot ignite because it is below its auto-ignition temperature.
  2. The liquid will self-heat and ignite without any ignition source.
  3. Vapour is being released at a temperature above the flash point, so an ignitable vapour-air mixture can form above the surface. Correct answer.
  4. Only the liquid surface can burn, so the vapour space is not a hazard.

Explanation

When the liquid temperature exceeds the flash point, sufficient vapour is produced to form a flammable mixture with air near the surface. An ignition source can then cause a flash fire, even though the bulk liquid is well below its boiling point.

Question 33Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A gas detector in a plant room reads 15 per cent of the lower flammable limit for methane. What does this reading indicate?

  1. The gas is at its stoichiometric concentration for complete combustion.
  2. The atmosphere is above the upper flammable limit and cannot burn.
  3. The concentration is well below the lower flammable limit and is not yet capable of propagating flame. Correct answer.
  4. The atmosphere is oxygen-deficient and entry should be refused.

Explanation

Readings expressed as a percentage of the lower flammable limit compare the measured concentration with the minimum concentration that will support flame propagation. A reading of 15 per cent LFL means the concentration is about one-sixth of that threshold, so it is not flammable but indicates a leak that must be investigated.

Question 34Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A closed 2 metre by 3 metre by 2.5 metre room contains 15 cubic metres of air. A gas leak adds 0.6 cubic metres of a gas whose lower flammable limit in air is 5 per cent by volume. What is the approximate concentration of gas in the room?

  1. About 2.4 per cent, below the lower flammable limit Correct answer.
  2. About 0.6 per cent, far below the lower flammable limit
  3. About 4.0 per cent, just below the lower flammable limit
  4. About 6.0 per cent, above the lower flammable limit

Explanation

The room volume is 2 x 3 x 2.5 = 15 cubic metres, so the added gas makes up 0.6 divided by 15, which is 0.04 or about 4 per cent of the total mixture. Because the lower flammable limit is 5 per cent, the mixture is still below it, although it is close enough to require ventilation and control of ignition sources.

Question 35Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

Which statement about the cooling effect of water applied to a fire is correct?

  1. Water mainly cools by absorbing heat as it warms and then vaporises, with latent heat accounting for most of the heat absorbed. Correct answer.
  2. Water has a higher latent heat of vaporisation than any other common extinguishing agent, so it works on all fuel types.
  3. Water cools only by conduction through the hose stream into the fuel.
  4. Water extinguishes fires solely by displacing oxygen from the compartment.

Explanation

Water absorbs sensible heat as it warms to boiling point and then absorbs a large amount of latent heat as it turns to steam. The vaporisation stage accounts for the greater part of the heat removed, which is why fine sprays are effective coolants.

Question 36Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A fire involving a spill of petrol is burning in a bund. Which foam application method gives the best chance of extinguishing it?

  1. Playing foam gently onto a surface ahead of the fire so it rolls across the fuel Correct answer.
  2. Applying foam from directly above into the centre of the flames
  3. Directing the jet into the burning liquid to agitate it
  4. Using a high-pressure water jet to break the foam into the fire

Explanation

Foam should be applied gently onto a surface such as the bund wall or the fuel ahead of the fire so that the blanket spreads across the liquid. This avoids plunging the foam into the fuel, which damages the blanket and can mix fuel into the foam.

Question 37Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A dry powder extinguisher is used on a small fire in a tray of cooking oil. What is the most likely outcome?

  1. The flames are knocked down but the oil may reignite because the powder provides little cooling. Correct answer.
  2. The fire is extinguished permanently because the powder seals the oil surface.
  3. The powder cools the oil below its flash point and prevents reignition.
  4. The powder reacts with the oil to form a soapy crust that seals the surface.

Explanation

Dry powder interrupts the flame chemistry and can rapidly knock down flames, but it has negligible cooling effect on the hot oil. Without cooling, the oil can remain above its fire point and reignite, which is why wet chemical agents are specified for cooking oil fires.

Question 38Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A high-rise building has a wet riser system. During a fire on the twelfth floor, the landing valve is opened but little water flows. Which cause is most consistent with a wet riser design?

  1. The sprinkler alarm valve has not operated.
  2. The fire damper on the floor has closed.
  3. The duty pump has failed or the system pressure is not being maintained. Correct answer.
  4. The riser is empty and must be charged by a pumping appliance.

Explanation

A wet riser is kept full of water under pressure by dedicated tanks and pumps, so poor flow points to a failure of the pump or pressure maintenance rather than an empty main. Crews should know the difference between wet and dry riser behaviour to diagnose the problem quickly.

Question 39Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A compartment fire has passed flashover and is now ventilation-controlled. A crew is about to open a door to make entry. Which combination of indicators best suggests a backdraught risk?

  1. Bright yellow flames visible through a window and a neutral smoke layer
  2. A well-established fire with flames projecting from a window opening
  3. Dark, turbulent smoke pulsing at gaps, windows stained with smoke and little visible flame Correct answer.
  4. A steady fire with a clear, high smoke layer and audible sprinkler operation

Explanation

Backdraught indicators include a fire that has used up available oxygen, producing dark smoke that pulses or is drawn inward at openings, together with smoke staining and an absence of visible flame. Introducing air by opening the door can then cause a sudden deflagration, so crews should cool the compartment from outside before entry.

Question 40Fire Engineering Science (combustion, fire behaviour, extinguishing agents, fire protection systems)

A sprinkler installation protects a warehouse with a high-piled storage hazard. Which design feature is most important for controlling a fire in this occupancy?

  1. Adequate design density and sprinkler coverage at the storage height, with attention to the ceiling-to-storage clearance Correct answer.
  2. Reliance on the wet riser landing valves instead of ceiling sprinklers
  3. A reduced design density because the high roof allows heat to escape
  4. Fewer sprinkler heads to reduce water demand

Explanation

High-piled storage creates a deep-seated fire that challenges sprinkler discharge, so design density and coverage must suit the storage height and commodity. Ceiling-to-storage clearance affects how quickly sprinklers operate and how effectively water reaches the fire.

Question 41Fire Fighting Operations, Equipment and Appliances

In a standard fire service hose layout, what does the term 'attack line' refer to?

  1. A short length kept on the appliance for washing down after incidents
  2. A hose used only for drafting from an open water source
  3. A large-diameter supply line laid from a hydrant to a pumper
  4. A hoseline deployed from the pump to deliver water onto the fire Correct answer.

Explanation

An attack line is the hoseline taken from the pump or appliance to the fire and used to apply water to the burning material. Supply lines, by contrast, move water from a source to the pump and are usually larger diameter. The distinction matters because attack lines are sized and manned for firefighting, not bulk water movement.

Question 42Fire Fighting Operations, Equipment and Appliances

Which type of branch is designed to produce a fine spray pattern for protecting crews and cooling hot gases?

  1. A solid-bore jet branch
  2. A high-pressure spray branch Correct answer.
  3. A foam-making branch
  4. A ground monitor

Explanation

A spray branch breaks the water stream into fine droplets, giving a wide cone that absorbs heat and shields firefighters from radiant heat. Solid-bore branches deliver a concentrated jet for reach and penetration but produce little spray protection. Foam branches and monitors serve different purposes entirely.

Question 43Fire Fighting Operations, Equipment and Appliances

What is the primary purpose of a self-contained breathing apparatus (SCBA) set at a fire?

  1. To filter smoke particles from the surrounding air
  2. To provide communication with the incident commander
  3. To cool the wearer's body during prolonged work
  4. To supply the wearer with clean air independent of the contaminated atmosphere Correct answer.

Explanation

SCBA supplies air from a cylinder carried by the wearer, so the user breathes clean air regardless of the smoke, toxic gases, or oxygen deficiency around them. It does not filter the ambient atmosphere, which is the role of a filter respirator. Cooling and communication are separate functions or secondary features.

Question 44Fire Fighting Operations, Equipment and Appliances

A length of delivery hose stored in a flat, folded configuration ready for quick deployment from an appliance is best described as which of the following?

  1. A hose reel
  2. A hose lay
  3. A hose pack or flat pack Correct answer.
  4. A suction hose

Explanation

A hose pack, often called a flat pack, is hose folded in a compact bundle so it can be carried or thrown and run out quickly. A hose lay describes the overall arrangement of hose from source to fire. A hose reel holds hose wound on a drum, and suction hose is rigid hose used for drafting.

Question 45Fire Fighting Operations, Equipment and Appliances

Which item of equipment is used to divide one incoming hoseline into two or more outgoing lines at an incident?

  1. A breeching (dividing) piece Correct answer.
  2. A collecting head
  3. A standpipe
  4. A hose clamp

Explanation

A breeching piece, also called a dividing breech, takes one inlet and splits it into two or more outlets so a single supply can feed multiple attack lines. A collecting head does the reverse, combining several inlets into one outlet. A hose clamp stops flow in a single line, and a standpipe provides an outlet from a riser or hydrant.

Question 46Fire Fighting Operations, Equipment and Appliances

When a ground monitor is set up to deliver a large jet at an incident, what is the main advantage over a hand-held branch?

  1. It can be repositioned more quickly by one firefighter
  2. It requires a smaller water supply than a hand-held branch
  3. It sustains a large flow without tying up firefighters to hold the reaction force Correct answer.
  4. It produces a finer spray than any hand-held branch

Explanation

A ground monitor is a mounted device that holds a large branch steady, so it can deliver high flows for long periods without firefighters absorbing the reaction force. It is slower to reposition and needs a substantial water supply. Its value is sustained volume with fewer personnel committed to holding the branch.

Question 47Fire Fighting Operations, Equipment and Appliances

What is the function of the non-return valve fitted to a pump's suction inlet?

  1. To mix foam concentrate into the delivery stream
  2. To allow water to flow only into the pump and prevent it draining back to the source Correct answer.
  3. To regulate the pressure of water leaving the pump
  4. To relieve excess pressure in the delivery hose

Explanation

A non-return valve at the suction inlet permits flow toward the pump but blocks reverse flow, so water does not drain back to the source when the pump stops or priming is lost. Pressure regulation, foam proportioning, and pressure relief are handled by other components. Keeping the pump and suction primed is essential for reliable drafting.

Question 48Fire Fighting Operations, Equipment and Appliances

Which of the following best describes the purpose of a hose clamp during a firefighting operation?

  1. To squeeze a hoseline shut so flow can be stopped while a length is changed or a branch is repaired Correct answer.
  2. To join two lengths of hose of different diameter
  3. To protect hose from abrasion where it crosses a wall
  4. To anchor a hoseline to the appliance

Explanation

A hose clamp compresses the hose to stop the flow of water, allowing a damaged length or branch to be replaced without shutting down the pump. Reducing couplings, hose anchors, and hose ramps or sleeves perform the other listed jobs. Clamps must be applied carefully to avoid damaging the hose jacket.

Question 49Fire Fighting Operations, Equipment and Appliances

A pumper is drafting from an open water source. Which condition most directly limits the theoretical lift of the pump?

  1. The temperature of the water in the source
  2. The number of branches in use
  3. The diameter of the delivery hose
  4. Atmospheric pressure acting on the water surface Correct answer.

Explanation

Drafting relies on atmospheric pressure pushing water up the suction hose as the pump creates a partial vacuum. At sea level atmospheric pressure supports a theoretical lift of about 10 metres, and losses reduce the practical figure. Delivery hose size, branch count, and water temperature affect flow and friction but not the fundamental lift limit.

Question 50Fire Fighting Operations, Equipment and Appliances

Friction loss in a hoseline increases in which way when the flow rate through the same hose is doubled?

  1. It falls because the water moves faster
  2. It stays the same because the hose is unchanged
  3. It increases by roughly four times Correct answer.
  4. It doubles in proportion to flow

Explanation

Friction loss varies approximately with the square of the flow rate, so doubling the flow through the same hose raises friction loss by about four times. This is why long or high-flow lines need higher pump pressure or larger hose. The relationship is a key part of pump pressure calculations.