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15 Cards in this Set
- Front
- Back
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Three ways a fire can be ventilated? |
Self Ventilation - occurs when the fire damages the structure of the premises, so that increased ventilation occurs Automatic ventilation - occurs when pre installed vents operate, usually in the early stages of a fire. Tactical ventilation - is used to assist firefighting operations and requires firefighters to release the products of combustion to allow fresher air to enter |
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Define ventilation |
The removal of heated air, smoke or other airborne contaminants from a structure, and their replacement with a supply of fresher air. |
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The benefits of tactical ventilation : |
• Assist the escape of occupants and firefighters by restricting the spread of smoke. • Improve conditions for firefighters and trapped occupants. • Speed up rescue operations and fire attack by reducing heat and smoke. • Increase the safety of firefighters by reducing risk of flashover, backdraft and fire gas explosion. • Reduce fire spread and property damage by controlling the movement of hot smoke and gases. • Improve visibility |
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The Basic Principles of Ventilation: |
• Hot gases should be released from the area at the greatest height possible and replacement fresh air should be allowed to enter at low level. • The high level vent should be downwind of the low level vent to take advantage of wind induced air flows. • The high level vent should be made before the low level vent. • If condition indicate signs of a potential backdraught, the compartment should be ventilated from outside the building where possible. • Outlet vents should be protected by firefighters in BA with charged branches. |
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Stages of the fire when tactical ventilation can be used: |
• After the arrival of LFB but before control is achieved. • After control but before fire extinction. • After fire extinction |
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Two types of tactical ventilation: |
Offensive and Defensive |
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Reason for defensive ventilations and how is it achieved ? |
Carried out away from the fire to improve access and escape routes for firefighting and searching conditions. It involves the venting of adjoining and outer compartments after the fire compartment has been isolated and suppressed |
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Reason for offensive ventilation and how is it achieved? |
Carried out directly to fire itself, to limit fire spread and improve conditions within the fire compartment. It also makes the approach route safer for firefighters. |
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Two types of tactical ventilations techniques(direction): |
• Vertical Ventilation • Horizonta Ventilation |
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When is vertical ventilation most appropriate? |
• The Fire is in or has spread to the roof space or tactical voids. • Where there are tall of vertical shafts within the building. |
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Advantages of vertical ventilation: |
• It minimises the risk of backdraft, as the overpressure in the compartment will drive out the hot gases. • It minimises fire spread, as the hot gases travel the shortest route before exiting the building. • It provides rapid smoke clearance because of the velocity of hot gases through the vent. |
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Disadvantages of vertical ventilation : |
• Firefighting operations may be required on the roof above the fire, which can be extremely hazardous. • There are fewer opportunities to make a vertical vent. |
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When is horizontal ventilation most appropriate ? |
• when vertical ventilation is not safe or possible and there are doors or windows close to the seat of the fire. |
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Before tactical ventilation can be undertaken, the IC must: |
• Undertake dynamic risk assessment. • Make sure adequate resources are available. • Identify the wind direction. • Decide whether vertical or horizontal ventilation is more appropriate. • Select inlet and outlet vents and decide how they will be made. • Make sure the outlet vent is covered by a charged 45mm hoseline. Make sure there is effective communication between firefighters performing other activities inside the building, the IC, and firefighters conducting ventilation activities. • Consider withdrawing any firefighters inside the building while ventilation takes place. • Notify all crew members of the intention to start ventilation. • Make an outlet vent first, followed by an inlet vent as soon as possible. • Closely supervise the effects of ventilation and make sure progress and conditions within the building are reported. |
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Size of inlet compared to outlet? |
Inlet should be twice the size of outlet. |
