Use of Positive Pressure Ventilation (PPV) Fans to Reduce the Hazards of Entering Chemically Contaminated Buildings

Fire fighters have used Positive Pressure Ventilation PPV fans to remove smoke from buildings before entry for rescue operations. A study was conducted to determine their effectiveness in removing chemical vapors from a building to afford quick rescue in the event that a terrorist bomb used chemical warfare agents. The testing was conducted in two phases. The first phase examined the ventilation rate of the building when PPV fans were used to determine the improvement in ventilation, and to determine how much vapor can be purged from a building within the first 10 minutes of PPV fan use. The second phase examined a mock rescue scenario in the same building by filling it with methyl salicylate and measuring the protection factor PF that fire fighters received while performing the rescue mission. This testing was performed according to standard Man in Simulant Test MIST procedures. Previous MIST testing of fire-fighter gear was used to compare the increased protection obtained through use of the PPV fans. The results show that the PPV fans were able to purge 47-72 of the vapors from the building within the first 10 min. The Ventilation rate was improved from 22 to 43 over the natural rate, depending upon the fan combination used. Protection of fire fighters was increased up to 27 times when the PPV fans were used. Bigger, gasoline-driven fans were better, and tilting the fans improved performance.