High pressure fans that direct air flow up the stairway of a burning high-rise building can increase the effectiveness of firefighters and the survivability of occupants by ridding the stairwell of smoke and toxic gases, according to a recent National Institute of Standards and Technology (NIST) report*.
The NIST analysis of 160 experiments conducted last year with small and large fans in the stairwell of a vacant 30-story office building in Toledo, Ohio, showed that the positive pressure ventilation (PPV) techniques used in small homes also worked in tall structures. The NIST engineers found that portable PPV fans, if used correctly, can both limit the amount of smoke and heat entering the stairway, and push smoke and deadly gases out of the structure. Data were collected with training smoke and pressure measurement devices.
Pressurization smoke control systems, which usually consist of mounted wall fans, have been incorporated into high-rise buildings since the 1970s. The NIST Toledo experiments, however, represented the first scientific evaluation of positive pressure ventilation technology using portable fans for buildings without built-in systems.
The NIST researchers developed several guidelines for the most effective use and positioning of portable PPV fans. The researchers also noted that the noise level near the working fans can go as high as 110 decibels—comparable to the level of a chainsaw—making communication difficult, and recommended that the fire command post be sited well away from the fans.
The NIST report urges further experiments to update current fan air flow performance standards for PPV needs. Manufacturers could certify air flow rates for specific fans. To aid fan selection, firefighter organizations also could use formulas that incorporate data for certified air flows with information related to the height or the volume of a building. NIST is continuing to study the use of PPV (see "NIST Test Fans the Flames for High-Rise Fire Safety".) A second series of tests, to be conducted later this summer with the assistance of the Toledo Fire and Rescue Department, will use actual fire in the PPV experiments.
The Department of Homeland Security's Science and Technology Directorate sponsored the Toledo PPV experiments. The Toledo Fire and Rescue Department, the Fire Department of New York and the Chicago Fire Department provided guidance and assistance during the experiments.
* Evaluating Positive Pressure Ventilation in Large Structures: High-Rise Pressure Experiments (NISTIR 7412) may be downloaded at www.fire.nist.gov/bfrlpubs/NIST_IR_7412.pdf.