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Positive pressure ventilation tactics (PPV)

There are three PPV tactics: offfensive, defensive and combinated fire ventilation tactics.

Blowing a large quantity of fresh air into a fire-affected space raises the internal pressure, allowing the smoke to be controlled.

The effects are rapidly obvious: Increased visibility, lowered temperature, reduced toxicity, control of smoke movement, and reduced calorific potential. These effects are beneficial to responders and trapped persons alike.

Firefighters must decide which fan or fans will be best in a given situation, depending on the layout of the premises to be ventilated.


OFFENSIVE PPV TACTIC

Tactique de VPP offensive.JPG


The offensive tactic is direct ventilation of the volume in which the fire is developing, combined with fire extinguishing resources.


This tactic aims to modify the behavior of the fire and quickly reduce its intensity.

 

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DEFENSIVE PPV TACTIC

Tactique de VPP défensive.JPG


This defensive tactic protects particular areas. It prevents smoke and hot gases propagating to locations that are to be protected.


Only volumes not affected by fire are ventilated.

This tactic employs ventilation dissociated from fireextinguishing actions.

It creates a logistical route with a slightly higher air pressure through which, for example, victims can be evacuated.

 

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COMBINED VENTILATION TACTICS

Also known as operational ventilation, this combined tactic involves using both the preceding tactics on high-rise tower blocks:


1/ Defensive ventilation is first deployed using a high-power "master" fan positioned at the foot of the building facing its entrance.

2/ With the stair well pressurized and thus made safe, the intervention team climbs up to the affected floor to set up a portable relay fan at the entrance of the burning volume.

3/ Once the exit is created, the offensive phase can begin: The air flow from the master fan is relayed by the secondary fan, which is on the affected floor, and pushes the hot toxic smoke out of the building so that the combustible materials of the smoke cannot spread. Smoke control facilitates the work of the teams, especially the fire extinguishing team.

 


Combined tactics.JPG

 

To see the video, click here