Smoke Control

Question 2

What is the primary cause of deaths in fire incidents?

Answer 2

Breathing in combustion products and smoke

Most deaths are not due to direct contact with flames or heat exposure.

Question 3

What percentage of fire deaths not directly due to burns is attributed to carbon monoxide?

Answer 3

85%

Carbon monoxide is the primary toxicant in fire-related fatalities.

Question 4

What are the two classes of toxic combustion products?

Answer 4

• Asphyxiant gases
• Irritant gases

Asphyxiants prevent oxygen uptake, while irritants cause immediate incapacitation.

Question 5

What is the effect of carbon monoxide (CO) on the body?

Answer 5

Prevents oxygen transport to cells by forming carboxy haemoglobin

This leads to central nervous system depression and potential death.

Question 6

How does hydrogen cyanide (HCN) compare in toxicity to carbon monoxide (CO)?

Answer 6

HCN is about 20 times as toxic as CO

HCN is produced from burning nitrogen-containing materials.

Question 7

What is the primary toxicant in poorly ventilated post-flashover fires?

Answer 7

Carbon monoxide (CO)

These fires have a very high yield of CO.

Question 8

What is the role of carbon dioxide (CO2) in fire situations?

Answer 8

Displaces O2, increasing breathing rate and depth

This can lead to accelerated inhalation of other toxicants.

Question 9

What happens to oxygen (O2) levels during a fire?

Answer 9

O2 is consumed, dropping from 21% to lower levels

Levels below 17% impair motor coordination.

Question 10

At what O2 level does a person lose consciousness?

Answer 10

6% to 10%

Immediate revival with fresh air or O2 is necessary to prevent death.

Question 11

Free card say thank you

Answer 11

Thank you

You’re welcome

Question 12

How does smoke typically travel during building fires?

Answer 12

Smoke travels to locations far away from the room of fire origin through door openings, leakage areas, cracks, and openings around pipes and ducts.

Question 13

What is the main driving force behind smoke movement in buildings?

Answer 13

The natural driving forces of buoyancy due to a change in density of the hot gases.

Question 14

What happens to smoke as it spreads and mixes with cold air?

Answer 14

It loses its buoyancy and descends to the floor, a process known as smoke-logging.

Question 15

What areas can become smoke-logged as a result of smoke spread?

Answer 15

Escape routes such as corridors, staircases, and lift shafts.

Question 16

What is a critical reason for controlling smoke movement in building fires?

Answer 16

To prevent smoke spread to escape routes, blocking occupant evacuation and hindering firefighting.

Question 17

What are the main objectives of smoke control systems?

Answer 17

• To limit smoke spread
• Reduce property loss
• Preserve fire resistance of buildings.

Question 18

How do smoke control systems contribute to the safety of building occupants?

Answer 18

By maintaining an acceptable, smoke-free environment along escape routes for safe evacuation.

Question 19

What effect does exhausting smoke and hot gases have on fire spread?

Answer 19

It reduces the accumulation of heat, slowing the rate of fire spread.

Question 20

What is one consequence of reduced accumulation of fire gases?

Answer 20

Avoids danger of flashover due to build-up of explosive gases.

Question 21

Fill in the blank: Smoke movement is driven mainly due to the natural driving forces of _______.

Answer 21

[buoyancy]

Question 22

True or False: Smoke-logging refers to smoke rising and remaining in the air.

Answer 22

False

Question 23

What are the two methods of smoke control?

Answer 23

1. Smoke Containment and Exhaust
2. Air Pressurisation of Escape Routes

These methods are used to manage smoke spread during a fire.

Question 24

What is the purpose of the ‘Smoke Containment and Exhaust’ method?

Answer 24

To contain smoke from a fire and exhaust it to the exterior

This method prevents smoke from spreading unnecessarily.

Question 25

What is the goal of 'Air Pressurisation of Escape Routes'?

Answer 25

To prevent smoke from entering escape routes ## Footnote This allows occupants to evacuate in a smoke-free environment.

Question 26

In which scenario is the 'Smoke Containment and Exhaust' method typically used?

Answer 26

When the fire occurs in the same space as the occupants or escape routes ## Footnote Commonly applied in atrium buildings.

Question 27

What happens to cold air when a fire occurs?

Answer 27

Cold air is drawn into the bottom of the hot smoke plume as it rises ## Footnote This increases the volume of smoke and gases.

Question 28

What role does a down-stand play in smoke containment?

Answer 28

Acts as a barrier to contain hot smoke in a reservoir ## Footnote Prevents smoke from traveling afar and losing buoyancy.

Question 29

What is the required clear layer height for smoke safety?

Answer 29

2.5 m ## Footnote This height allows for clear visibility for escape and reduces heat radiation exposure.

Question 30

How does the natural buoyancy of smoke affect its removal?

Answer 30

It drives hot smoke through natural vents ## Footnote Larger areas may require exhaust fans to assist in this process.

Question 31

Quantity of smoke removed must...

Answer 31

- Equal the quantity of air entering the plume - To ensure smoke layer remains at a safe level.

Question 32

What happens if sufficient air does not enter the space during smoke removal?

Answer 32

- Smoke exhaust system will draw air from leakage areas, - Compromising effectiveness - Increase in fire size.

Question 33

At what level should replacement air supply enter to ensure proper buoyancy?

Answer 33

Low level ## Footnote This allows the air to contact and be heated by the fire or hot smoke.

Question 34

What is the maximum face velocity of air supply to prevent hindrance to evacuees?

Answer 34

5.0 m/s ## Footnote Exceeding this velocity may obstruct the movement of evacuees.

Question 35

What is the minimum clear height below the smoke layer for safe evacuation?

Answer 35

2.5 metres ## Footnote This height allows occupants to evacuate in a clear breathable layer.

Question 36

What is the main purpose of maintaining a clear smoke layer?

Answer 36

- To permit occupants to evacuate in a clear breathable layer - Aid firefighting operations ## Footnote A clear layer improves visibility and air quality for those escaping.

Question 37

What is the lowest acceptable temperature of the smoke layer to prevent loss of buoyancy?

Answer 37

18°C above ambient ## Footnote Maintaining this temperature helps ensure that the smoke layer remains buoyant.

Question 38

What temperature of the smoke layer can cause severe pain and discomfort to occupants?

Answer 38

More than 200°C ## Footnote High temperatures from the smoke layer pose significant risks to safety during evacuation.

Question 39

Fill in the blank: The design hot smoke layer base must be above the heads of people escaping underneath it at a minimum height of _______.

Answer 39

2.5 metres

Question 40

True or False: The smoke layer should be maintained at a temperature below 18°C to ensure safety during evacuation.

Answer 40

False ## Footnote The smoke layer must be at least 18°C above ambient to maintain buoyancy.

Question 41

What is the primary risk associated with open atriums in buildings during a fire?

Answer 41

Smoke can spread rapidly to other floors or accumulate in the atrium ## Footnote This poses a significant risk to occupants and responders.

Question 42

What is the height to which smoke curtains drop when activated?

Answer 42

1.8 metres ## Footnote Smoke curtains are made of flame-resistant fabric.

Question 43

What are the main purposes of smoke curtains?

Answer 43

* Keep smoke out of occupied spaces * Help create a smoke reservoir * Guide smoke towards the atrium roof for exhaustion ## Footnote This facilitates safe evacuation and easier access for firefighters.

Question 44

How can smoke curtains be managed when not in use?

Answer 44

They can be retracted and concealed ## Footnote This feature allows for unobstructed use of the atrium.

Question 45

What is the function of an air pressurisation system?

Answer 45

To keep areas smoke-free by increasing air pressure ## Footnote This protects areas like staircases relative to the area on fire.

Question 46

How does an air pressurisation system help during a fire?

Answer 46

It blocks smoke from entering protected areas ## Footnote This allows for safe evacuation and navigation for firefighters.

Question 47

What does the air pressurisation fan do in a smoke control system?

Answer 47

Pushes smoke to exhaust from the building through smoke vents ## Footnote This is essential for maintaining clear escape routes.

Question 48

In which situations are air pressurisation systems required to be installed in staircases?

Answer 48

* Buildings exceeding 24 m in height with no natural ventilation in staircases * Buildings with more than 4 basement storeys where exit staircases connect to the firefighting lobby in the basement ## Footnote Each staircase must have its own pressurisation system.

Question 49

True or False: Smoke curtains can only be used in buildings with natural ventilation.

Answer 49

False ## Footnote Smoke curtains are effective in various building designs.

Question 50

What is the main purpose of the air pressurisation system in a staircase during a fire?

Answer 50

To prevent smoke from infiltrating into the staircase via gaps and cracks.

Question 51

What must all doors separating the staircase and occupied spaces be fitted with?

Answer 51

Automatic door closers.

Question 52

What is the required pressure difference maintained by the air pressurisation system when doors are closed?

Answer 52

About 50 Pa.

Question 53

What is the significance of maintaining a pressure differential of 50 Pa?

Answer 53

It prevents smoke from infiltrating from the fire space to the escape staircase.

Question 54

What force is equivalent to a pressure of 50 Pa across a door?

Answer 54

110 N at the door handle.

Question 55

Why should the pressure differential not exceed 50 Pa?

Answer 55

It will be difficult for the elderly to open the door.

Question 56

What mechanism is provided to prevent over-pressurisation in the staircase?

Answer 56

An air pressure relief valve.

Question 57

What happens when the pressure differential exceeds 50 Pa?

Answer 57

The air relief valve opens to allow air to be released to the building exterior.

Question 58

What is the fan capacity designed to maintain during door openings?

Answer 58

A pressure difference of 50 Pa.

Question 59

Why must doors on two successive floors and the main discharge door be opened?

Answer 59

To allow occupants to evacuate and firefighters to access the staircase.

Question 60

What is the minimum air velocity required through an open door to prevent smoke entry?

Answer 60

1.0 m/s.

Question 61

What is the consequence of not maintaining a minimum air velocity of 1.0 m/s during door openings?

Answer 61

Smoke may enter the pressurised staircase.

Question 62

Fill in the blank: The air pressurisation system must maintain a pressure difference of _______ between the pressurised staircase and the occupied space.

Answer 62

50 Pa

Question 63

True or False: The pressure differential across the door helps occupants open the door easily during a fire.

Answer 63

False

Question 64

What are the two methods of operating pressurisation systems?

Answer 64

Single-Stage Operation and Two-Stage Operation

Question 65

In Single-Stage Operation, when does the pressurisation fan run?

Answer 65

Only when the fire alarm system has been activated

Question 66

What is the basic weakness of Single-Stage Operation?

Answer 66

Delay between the start of a fire, its discovery, and the starting of the pressurisation fan

Question 67

Why is the operation of pressurisation during the early stages of a fire important?

Answer 67

Large quantities of smoke can be generated through incomplete combustion

Question 68

In Two-Stage Operation, when is the pressurisation fan system in operation?

Answer 68

Whenever the building is occupied

Question 69

What additional function does the pressurisation fan serve in Two-Stage Operation?

Answer 69

It meets the normal ventilation requirements of the pressurised space

Question 70

What is a key benefit of Two-Stage Operation compared to Single-Stage Operation?

Answer 70

Prevention of smoke spread during the early stage of a fire

Question 71

Why are the fan and associated equipment likely to be in good maintenance condition in Two-Stage Operation?

Answer 71

They are in constant operation

Question 72

What risks do fires in basements pose?

Answer 72

High heat buildup and unexpected floor collapse

Question 73

Why is adequate air pressurisation needed in basement staircases?

Answer 73

To prevent hot smoke from traveling through the staircases

Question 74

Where must smoke vents be distributed in basements?

Answer 74

Along the perimeter of the basement

Question 75

What must be provided for each basement floor?

Answer 75

Separate ducts and vent outlets

Question 76

Fill in the blank: In a fire situation, the Two-Stage Operation will run in __________ mode after the fire alarm system is activated.

Answer 76

pressurisation

Question 77

True or False: In Single-Stage Operation, the pressurisation fan runs continuously.

Answer 77

False