Positive pressure ventilation tactics (PPV)
There are three PPV tactics: offensive, defensive and combinated firefighting 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
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
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.
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INTERACTIVE TRAINING COURSES - firefighting VENTILATION
Test yourself with our free interactive courses available at this link : http://leader.educexpert.com/
Their aim is to:
- Recall the main principles on fire,
- Explain the thermal phenomena
- Train learners to the concept of fire ventilation in intervention according 3 main techniques (Offensive, defensive and combined fire ventilation tactics).
Each part includes a self-assessment for rapid validation of the learner.
LEADER, well-known firefighting equipment manufacturer, offers a wide range of PPV firefighting fans.
Discover our other expertises on firefighting fans and firefighting ventilation (PPV, NPV, operational ventilation, etc).