Positive Pressure Ventilation Research

NIST Releases DVD Set on Positive Pressure Ventilation Research
This new DVD set includes a presentation video that explains PPV, examines the results of NIST's PPV research, and closes with a focus on the use of PPV tactics in high-rise buildings. All of the NIST PPV reports referenced in the presentation are included on Disc 1 of the set. All of the videos from the high-rise fire experiments are also provided with a user-friendly, graphic menu that can be used on a PC or a DVD player. NIST, with support from USFA, DHS, and fire departments across the country, has taken engineering principles and applied them to fire service PPV tactics in order to improve fire fighter safety. To receive a copy of the DVD, send email to skerber@nist.gov with your name and mailing address.

Positive Pressure Ventilation
The objective of this research is to improve firefighter safety by enabling a better understanding of structural ventilation techniques, including positive pressure venting (PPV) and natural venting. In addition, by examining structural fire ventilation using full-scale fire experiments with and without PPV using the NIST Fire Dynamics Simulator (FDS), a technical basis for improved training in the effects of ventilation on fire behavior was provided.

Characterizing Positive Pressure Ventilation using Computational Fluid Dynamics
Full-scale experiments were conducted to characterize a Positive Pressure Ventilation (PPV) fan, in terms of velocity. Experiments were performed in an open atmosphere and in a simple room geometry. The results of the experiments were compared with Fire Dynamic Simulator (FDS) output. The measurements of both sets of experiments compare favorably with the FDS model results. With the correct geometry, vent placement, and boundary location FDS predicted velocities that were within 10 percent for the open atmosphere and 20 percent for the simple room geometry. The Smokeview visualization of the FDS results of the PPV fan's flow pattern, and the flow out of the window also correlated well with those measured experimentally.

Effect of Positive Pressure Ventilation on a Room Fire
Fire departments may use ventilation blowers or fans to pressurize a structure prior to suppressing a fire. This pressurization or positive pressure ventilation (PPV) tactic can assist in the venting of smoke and high temperature combustion products and make attacking the fire easier than without PPV. However, this tactic also provides additional oxygen to the fire and can increase the rate of heat and energy being released. PPV has not been characterized carefully enough to establish specific guidelines for optimum use.

This study examined gas temperatures, gas velocities and total heat release rate in a series of fires in a furnished room. The use of the PPV fan created slightly lower gas temperatures in the fire room and significantly lower gas temperatures in the adjacent corridor. The gas velocities at the window plane were much higher in the PPV case than in the naturally ventilated scenario. This higher velocity improved visibility significantly. PPV caused an increase in heat release rate for 200 seconds following initiation of ventilation but the heat release rate then declined at a faster rate than that of the naturally ventilated experiment.

http://www.fire.gov/PPV/index.htm