Element 7: Principles of Fire Initiation & Spread & Fire Risks Caused by Construction Activities.

Question 1

What are five classifications of fires according to fuel type?

Answer 1

1) Class A - Solid materials, paper, wood, coal, packaging material & textiles.
2) Class B - liquids or liquefiable solids, petrol, diesel, paraffin, oil, grease.
3) Class C - Gases, methane, propane, butane, acetylene & mains gas.
4) Class D - Metals, eg. Aluminium, magnesium.
5) Class F - High temperature fat.

Question 2

What are 4 basic principles of heat transmission & fire spread?

Answer 2

• Convection - Hot gases from fire rise up & ignite combustible materials. Outdoors convection currents carry hot embers which can carry fire to another location.
• Conduction - Heat transmitted through solid materials.
• Radiation. Infrared waves travelling in straight lines can pass through transparent surfaces.
• Direct burning- Flame spreads through material on fire til all consumed.

Question 3

Identify 3 ways of stopping a fire.

Answer 3

• Remove oxygen - smother (fire blanket, foam, dry powder).
• Remove heat - cool with water or carbon dioxide
• Remove fuel - turn off gas/electricity/oil supply

Question 4

What 3 topics should a fire risk assessment address?

Answer 4

1) A site plan
2) The fire hazards & their level of risk
3) Fire control & evacuation measures

Question 5

What considerations should be made when identifying fire hazards in risk assessment?

Answer 5

Looking around construction site, including existing buildings being worked in & temporary accommodation for sources of heat, fuel & oxygen which together might lead to fire.

Question 6

What should site emergency plan cover & where should it be kept?

Answer 6

Location of all main fire hazards & protective measures on site.

Kept in Construction Phase Plan.
Precautions identified will become part of site induction.

Question 7

How might you minimise risk of fire in woodworking area?

Answer 7

Ensuring that wood shavings & dust are cleared regularly & ignition sources such as sparks from electrical equipment do not come in to contact with combustible materials.

Question 8

What precautions should be taken when using flammable liquids?

Answer 8

• Volume minimised (up to 250l usual).
• Held in appropriate (usually metal), correctly labelled containers with secure lids.
• Decanting from one container to another minimised reducing risk of spillage.
• Storage area well ventilated.
• Drip trays & proper handling aids provided.
• Method for dealing with spillages & disposal of empty containers & contaminated waste required.

Question 9

What are hazards associated with LPG?

Answer 9

LPG is colourless liquid which evaporated into gas to form flammable or explosive mixture. Heavier than air can collect in drains gullies cellars & excavations where it can accumulate & lead to possible asphyxiation. Not easily detected by smell.
Can cause frost/ cold burns to skin & risk of fire or explosion especially in unventilated places.
Cylinders vulnerable to impact from equipment near. Leaks from faulty valves & pipe connections.
Cylinder give rise to manual handling problems & proper risk assessment required.

Question 10

What are requirements for safe storage of LPG?

Answer 10

• Cylinders should be stored upright (unless designed otherwise- LPG fuelled forklift trucks)
• Stored in suitable containers with valves uppermost, open air position protected from sunlight & falling material.
• Storage areas Suitably signed, warning sign where explosive atmosphere can occur.
• LPG storage is classified as hazardous place, i.e. in zonal classification.
• Not stored beneath beneath overhead cables or in path of falling materials.
• Planning- to ensure no. Of cylinders kept small as reasonable.
• Clearly marked “Highly flammable LPG, with design pressure & temperature.
• Correct regulators used & pipe colour coded orange.
• Not stored next to oxygen or other flammable gases, e.g. Acetylene or oxidising agents, or near any cellars, drains, excavations.
• Full stored separately to empty & separate from bulk containers.
• Suitable fire extinguishers available in event of accident (foam/powder).

Question 11

13. Upon what does fire resistance for
    Timber depend?

Answer 11

Four T’s
• Thickness (cross sectional)
• Tightness of any joints involved.
• Type of wood
• Treatment received

Question 12

Upon what does fire resistance for reinforced concrete depend?

Answer 12

• Type of aggregate used.
• Thickness concrete over reinforcing rods.

Question 13

Upon what does fire resistance for a brick wall depend?

Answer 13

• Thickness
• Applied Rendering/plastering
• Load bearing or not.
• Perforations/cavities within bricks

Question 14

Describe affects of fire on unprotected steel beam.

Question 15

Describe how flame retardant paint protects covered timber.

Answer 15

Bubbles rather than burns thereby giving added protection

Question 16

Describe conditions that determine 3 zones used to identify hazard areas (UK DSEAR)

Answer 16

• Zone 0 - explosive atmosphere present continuously or for long periods.
• Zone 1 - explosive atmosphere likely to occur in normal operation.
• Zone 2 - explosive atmosphere not likely to occur in normal operation, if it does, it is only short time.

Question 17

What are limitations of manual alarm system & how May they be overcome?

Answer 17

• Only raise alarm limited area for limited time.
• Overcome with means for person raising alarm to make it more widespread - Phone, public address system, manual/ electric system.

Question 18

Identify the 3 ways in which fire may be detected and state the types of automatic detector associated with each.

Answer 18

• Smoke/Fumes by ionisation or optical smoke detector.
• Flames by ultraviolet & infrared radiation detector.
• Heat by fusion or expansion heat detectors.

Question 19

Identify classes of fire for which water is suitable.

Answer 19

Water - Class A

Question 20

Identify classes of fire for which carbon dioxide gas is suitable.

Answer 20

Carbon dioxide Gas - Class B & electrical fires).

Question 21

Identify classes of fire for which Dry powder is suitable.

Answer 21

All classes except F

Question 22

Identify classes of fire for which foam is suitable.

Answer 22

Foam- Class A&B (Specialist foams for elec fires)

Question 23

Identify classes of fire for which Fire Blankets are suitable.

Answer 23

Classes B & F

Question 24

State colour coding requirements for portable fire extinguishers.

Answer 24

• Water - white lettering.
• Carbon dioxide - black.
• Foam - Cream.
• Dry powder - Blue.
• Halon - Green (rare)

Question 25

Outline main points to be covered in training in use of fire extinguishers.

Answer 25

• General understanding how to operate.
• Importance if correct extinguisher for different classes of fire.
• Practice in use of different extinguishers.
• When & when not to tackle fire.
• When to leave fire that’s not been extinguished.

Question 26

What is purpose of signs used along escape route?

Answer 26

To direct occupants to the means by which they can safely leave premises.

Question 27

Outline main requirements for escape route

Answer 27

• Clearly signed.
• Short & Straight as possible.
• Lead directly to place of safety.
• Be clear of obstructions/materials that could cause fire hazard.
• Well lit.
• Wide enough for unrestricted flow of people.

Question 28

What is an assembly point & how might it differ from refuge?

Answer 28

Place of ultimate safety (outside building in open air away from any further danger from the fire); a refuge is is a temporary place of comparative or relative safety, in fire protected area (usually within building)

Question 29

What should take place at assembly point following evacuation?

Answer 29

Roll call to ensure all people from affected area present.

Question 30

What are Fire marshals/Wardens responsible for?

Answer 30

• Ensuring all occupants leave.
• Searching all areas to ensure people are clear.
• Ensuring fire escape routes are open and clear at all times.
• Ensuring all doors & windows closed on leaving the area.
• Conducting roll call at assembly (in absence of senior management)
• Meeting fire service on arrival & informing them of any relevant details.
• Ensuring special assistance available for disabled & infirm. Evac chairs.
• Investigating location of fire.