Chapter 16: Ventilation Flashcards
Ventilation
As applied to firefighting is the planned and systematic, release and removal of heated air, smoke and toxic gases from a confined area and controlled replacement of these products of combustion with a supply of cooler, fresh air
Presure and Heat transfer
both move from an area of high to an area of low
and will follow the path of least resistance
Advantages of Ventilation
- Rescue op.: makes atmosphere in the structure more tenable
- Fire attack: easier to rapidly extinguish.
- Property damaged minimized
- Thermal layering: disturbance is minimized
- Reduce backdraft/flashover
- Fire spread: tends to localize fire
Mechanics of ventilation
regardless of how its achieved,its simply the movement of air from high-pressure location to a lower pressure location
Vertical & Horizontal Ventilation
-Can be achieved through Natural, Forced: Mechanical, Hvac, and Hydraulic means
when ventilating you want the wind at your back
Vertical Ventilation
Defined as the vertical Channeling of heat, smoke, and gases which is achieved by creating an opining above the fire either by means of existing openings or by cutting the roof. Vertical ventilation provides an opening for the rising and expanding smoke and fire gasses to leave the structure
when doing Vertical Ventilation…
Always wear PPE & SCBA
- Work on windward side of hole
- Have a charged hose line for safety
- Do not throw Debris on crews below
- Always sound the roof before you move
4 types of roof cuts
Kerf Cut: slot cut width of chain to determine direction of fire spred
Inspection cuts: Small Tri angle
Louvered Cut: large rectangular openings
- length-ways: 3 rafters - width wise between 4 rafters
Trench cuts
5 things to consider before opening a roof
Location of seat of fire Wind Direction Extent of Fire Obstructions Exposures
Horizontal Ventilation
Defined as the horizontal channeling of heat, smoke and gases through wall openings such as windows and doors allowing cooler air to enter
when doing Horizontal Ventilation…
it uses natural openings
open leeward side first
Windward side second
NPV
Use mechanical means to develop artificial circulation to pull or draw products of combustion of a structure
generate low pressurer gradient inside
PPV
Use mechanical means to create a positive pressure gradient that pushes the products of combustion from a structure
dont fight the wind
air should be introduced from un burnt side
exit to same size or smaller than opening
Do not PPV if
Fire is ventilation controlled / under ventilated state.
if we add air+ back draft, flashover, smoke explosion
pluses of PPV
can be done from outside the structure
it can be controlled
flow path can be direct away from points of egress
equipment does not block door ways
