Mechanical Ventilation Flashcards
Define PPA
Positive Pressure Attack
- Used during the initial stages of an incident ton make the structure safer for fire attack.
- It consists of directing one or more high-output fans into the building in order to increase the pressure inside the building relative to atmospheric pressure outside.
- The pressure difference directs smoke and toxic gases and heat from the entrance where the fans are to the exhaust opening located as close to the fire as possible.
Define PPV
Positive Pressure Ventilation
- Similar to to PPA, except its used for purposes other then fire attack.
- eg. Make area safer for overhaul or clear out hazardous gases and smoke
Define PPP
Positive Pressure Pressurization
- Uses one or more high-output fans to over-pressurization an enclosed compartment, thereby preventing additional smoke and toxic gases and heat from entering. Usually don’t use an exhaust opening.
Define flowpath
- Volume between an inlet and an outlet that allows the movement of heat and smoke from the higher pressure within the fire area towards the lower pressure areas accessible via doors and window openings
- Maybe several flow paths
- Operations in the flow path are significantly more dangerous due to increase flow of smoke, heat and fire
What method of ventilation is commonly used in strip malls or single family detached homes to help reduce extension to neighbouring homes?
PPP
How many fan position set ups are there?
5
single series parallel combination v-point
The basic set up used to ventilate most residential fires. May not be sutable is there is limited access to the door or fan can’t be places to create a full season the door.
Single (basic)
One fan placed behind another. The further fan ensure a full seal and provide 30% more air.
Series
What fan set up provides 30% more air?
Series
If the entrance door is wider then normal, fans maybe placed side by side. Number of fans depends on size of enterance.
Parallel
When you combine the series and parallel patterns to effectivly vent a wide opening
Combination (wider openings)
This provides the highest volume of air
V-point
two fans may be positioned parallel to, and several feet away from each other in a v shape. One fan can seal the top, while the other seals the bottom. 10% more air then series or parallel
10% more air then series or parallel vent
V-point
When should interior crews immediately evacuate the structure or seek a safe location.
when there is sudden changes in conditions like
- reduced visibility
- rapid lowering of smoke or thermal layer
- higher heat
what is used to:
- reduce the risk of back draft or flashover occurring to facilitate rescue
PPA
What is used to:
- make an area more tenable for victims and firefighting to remove toxic, explosive and super heated gases
PPA
what is used to:
- to enable crews to advance more rapidly to the seat of the fire
PPA
what is used to:
- help protect firefighters who are extinguishing the fire by removing steam
PPA
What is used to:
- to make an area safer for salvage and overhaul
PPV
what is used to:
- to make salvage and overhaul more effective
PPV
what is used to:
- to remove toxic, explosive, and super heated gases
PPV
what is used to:
- to decrease property damage
PPV and PPP
what is used to:
- prevent toxic, explosive, and super heated gases from spreading to exposures
PPP
what is used to:
- to confine the fire
PPP
what is used to:
- to protect exposures
PPP
what is used when:
- conditions are untenable for firefighter entry due to heat, smoke, and toxic gases
PPA
what is used when:
- the construction is unsuitable for natural ventilation due to the lack of vertical shafts or horizontal exterior openings
PPA
what is used when:
- the fire is below ground level, in a confined space, or where it is difficult to gain entrance
PPA
How big should the exhaust opening be for PPA?
3/4 to 1 3/4 times the size of the entrance. bigger is better
Without a total proper seal, what can PPA’s additional convection currents create?
flashover conditions
