Making vents Open windows where possible Cover exit vents with jets Ensure no-one working above vent Fresh air may result in backdraught, withdraw all personnel from danger area Glass may travel long distances.
Inlet and outlet vents - Same window Viewed from inside the room.
Forced ventilation - Disadvantages It requires mechanical device Can increase the intensity of the fire If large compartment - large fan or several smaller ones needed Time to set up When used defensively it means a room by room approach.
Main techniques Positive pressure ventilation (PPV) Negative pressure ventilation (NPV) Heating, ventilation and air conditioning systems Powered exhaust systems.
Defensive PPV - Advantages Rapid removal of gases Cooler and easier working conditions Hot spots seen easier - have hose line to deal with.
PPV sequence of operations Isolate unaffected areas Position the fan Crew members to open exhaust vent Start the fan Check smoke taking expected route Monitor until fan stopped.
Offensive PPV Used before the fire is out Part of firefighting tactics If not used effectively can cause fire spread.
Summary Note and use prevailing wind Consider and use correct tactic Do firefighters need to withdraw Outlet first - high and downwind Cover outlet vents with charged hoselines Start inlet vent Communications Monitor.
Confirmation Assessments will be based on this lesson and the corresponding study note Learning Outcomes Describe the effects of forced and natural ventilation on the development of a range of fires.