1. Principles of Positive Pressure Ventilation

2. Principles of Positive Pressure VentilationVIDEO2KEY CONCEPTS: REDUCE HEATREDUCE SMOKEIMPROVE VISIBILITYCOMMUNICATION 3. Principles of Positive Pressure Ventilation3OVERVIEW I. PRINCIPLES OF PPV II. LOCATIONIII. MANAGING AIRFLOW IV.SUCCESSFUL PPVV. OPERATIONAL CONSIDERATIONS VI.ADVANTAGES AND DISADVANTAGES OF PPV 4. Principles of Positive Pressure Ventilation4Principles of PPV A. Use to supplement natural airflow 1. Note prevailing wind direction 2. Do not try to reverse convection What is convection? The transfer of heat energy by the movement of heated liquids or gases (heated air and gases rise) A. Use high volume fans B. Create pressure differential 1. High pressure inside 2. Low pressure outside C. Smoke seeks an outlet through an opening controlled by fire fighters 4 5. Principles of Positive Pressure Ventilation5Principles of PPVUse high volume fansGasElectric5 6. Principles of Positive Pressure Ventilation6Principles of PPV Create pressure differential High pressure inside Low pressure outside6 7. Principles of Positive Pressure Ventilation7Location A. Outside of building 1. Fans produce carbon monoxide B. At lowest point of building C. Cone of air must fully cover opening 8. Principles of Positive Pressure Ventilation8Managing Airflow A. Systematic process 1. Exhaust opening should be smaller than input opening 2. A single exhaust opening is preferred a) Multiple exhaust openings will reduce effectiveness 3. If size of exhaust openings exceeds size of input opening positive pressure will be lost B. Direct airflow by opening and closing doors 1. Work one room at a time C. Multistory buildings 1. Apply airflow at lowest level of building a) Use stairwells or vertical shafts to direct airflow 2. Work one level at a time a) Begin with level most heavily charged with smoke b) Open and close doors to direct airflow 1. Smoke can be directed out exterior openings on fire floor 2. Smoke can be directed up vertical shafts that extend through the roof 9. Principles of Positive Pressure Ventilation9Successful PPV A.Good communications B.Discipline C.Building occupants may compromise operations 1.Occupants leaving building may alter airflow 2.Curious occupants open doors and interfere with operations 3.In large buildings it may be necessary to detail personnel to patrol openings 10. Principles of Positive Pressure Ventilation10Operational Considerations A. Exhaust openings 1. PPV is not effective if smoke and heat have no where to go (vertical ventilation) 2. Remove screens, etc. B. Fan placement 1. Spot fan so that cone of air covers entire opening 2. Multiple fans can be used for large openings a) Arrangements include side by side, stacked, inline 3. PPV fans will introduce small amounts of carbon monoxide into buildings (from exhaust) 11. Principles of Positive Pressure Ventilation11Advantages & Disadvantages of PPV A. Advantages 1. Set up without entering building 2. Most efficient forced ventilation technique 3. Effective in very large buildings B. Disadvantages 1. Structure must be intact (crews must have the ability to control openings) 2. Introduces carbon monoxide into structure (exhaust-gas fan) 3. May extend hidden fires 12. Principles of Positive Pressure VentilationVIDEO-Bad PPVKEY CONCEPTS: COMMUNICATIONEGRESSVERTICALPLACEMENT12 13. Principles of Positive Pressure Ventilation