A series of full-scale experiments were conducted in a three-story fire fighter training burn building to compare natural ventilation with positive pressure ventilation. A wood pallet and dry hay fire was allowed to burn in the structure with all doors and widows closed until the fire reached an oxygen-limited state. A door and window were then opened and the structure allowed to either undergo natural ventilation or a positive pressure fan was started in front of the door to ventilate the structure. Fourteen different configurations of fire room and vent locations were examined, each with both natural and positive pressure ventilation. Gas temperatures, air velocities, fire room oxygen concentrations and differential pressures were recorded and compared for the different configurations and ventilation techniques. The data indicates that using correct ventilation scenarios resulted in lower temperatures within the structure at the 0.61 m (2 ft) height, where victims may have been located, and at the 1.22 m (4 ft) height, where fire fighters may have been operating. There were only a few ventilation configurations where the temperatures in rooms other than the fire room exceeded the victim or fire fighter threshold temperatures with either ventilation technique. The use of positive pressure ventilation caused the fire to grow more quickly and in some cases created higher temperatures at the lower elevations within the structure. The use of PPV ventilation resulted in visibility improving more rapidly and in many cases cooled rooms surrounding the fire room.
Citation: NIST Interagency/Internal Report (NISTIR) - 7342
NIST Pub Series: NIST Interagency/Internal Report (NISTIR)
Pub Type: NIST Pubs
air flow, air velocity, fan, fire fighter, positive pressure ventilation, PPV, tactics, ventilation