16 Ventilation Flashcards
Define ventilation?
Ventilation, as applied in firefighting, is the planned and systematic release and removal of heated air, smoke and toxic gases from a confined area and the controlled replacement of these products of combustion with a supply of cooler fresh air.
What 4 factors must the FF consider pertaining to smoke?
- Volume
- Velocity
- Density
- Colour
3 different cuts for roof ventilation openings?
- Kerf cuts
- Inspection cuts
- Louvered cuts
Find where you want the opening and think about the following?
- Location of seat of fire
- Wind direction
- Extend of the fire
- Obstructions
- Exposures
Who does ventilation have to be coordinated with?
Ventilation must be coordinated with fire attack - it is a systematic and controlled process involving coordination of which areas to ventilate. (ex. breaking windows, opening doors, roof cuts etc.)
What are the means of achieving vertical or horizontal ventilation?
- Natural
- Forced/Mechanical
- Electric fans
- Hydraulic
- Heating, ventilation and air condition systems (HVAC)
What are the disadvantages of negative pressure ventilation (NPV) ?
- Equipment block access and egress to the structure
- FF must enter the the structure to initiate NPV
- Equipment gets exposed to contaminants
- Not effective in high ceiling structures
- Produces additional noise within the structure
- Must be used with electric fans only
- Less adaptable to situation
- Less effective than PPV
- Depends on a power source (electricity, fuel)
- Requires special equipment
When should positive pressure ventilation (PPV) not be used?
Where the fire exists in an under-ventilated state or where any warning signs preceding backdraft are apparent!
It is well established that the addition of air into an under ventilated compartment could possibly trigger a backdraft, smoke explosion or even flashover.
What are the advantages of PPV?
- can be established without entering contaminated environments
- Air currents are kept to a minimum
- Equipment does not block doorways
- Internal combustion equipment operates more efficiently (gas operated fans)
- Equipment cleaning and maintenance is reduced
- Noise levels are reduced within the fire building
- It is effective in all types of occupancies
- Heat and smoke can be directed away from paths of egress
- It can be controlled
- It is more effective than NPV or HV
What are the disadvantages of PPV?
- Must be coordinated with other sectors
- Introduces large volumes of air into a structure that if misdirected will intensify and spread the fire
- Requires special equipment
- Depends on a power source (water, electrical, fuel)
What % of the opening has to be covered, when ventilating with a fog stream (Hydraulic ventilation) ?
85 - 90%
How far back does the nozzle tip have to at least be from the opening for HV?
At least 2 ‘ or 0.6m
When are FF allowed to switch of the HVAC system?
- when no qualified person is available
2. If it is a simple on and off switch
Before attempting Hydraulic ventilation the fire must be?
- placed under control to prevent further fire damage
2. contact fire command prior to ventilating
The intensity of the stack effect will depend on?
- How air tight the building is
- The distance between the upper and lower openings
- the difference between the inside and outside temperature
The greater the distance between upper & lower openings and the difference in temp. the more intense the stack effect will be.
