A Study on Design Methodologies of Smoke Venting Systems (Part 1 - Field Measurements of Air Flow Rates and Pressure Differences)

Abstract

It is well known that excessive depressurization caused by the mechanical smoke exhaust system creates difficulties in opening and closing the doors. This will also increase smoke leakage into depressurized areas. It is difficult to estimate flow rates and depressurization due to the lack of available data concerning the leakage of building elements other than the leakage around the doors.
Therefore, the authors took measurements in a nine story office building and carried out a computer simulation, then compared the data. The results of the measurements show that with all the doors closed the required force to open the door reached 8.2 [kgf], and the 70% of the exhaust volume comes through gaps in the doors, (15% from the assumed fire room, the rest from other rooms). The remaining 30% comes from gaps in fixtures, ceilings, air ducts and pipe shafts, for which the effective flow area amounts to 0.039 [m²].
In order to estimate the flow rates and depressurization through the computer simulation, a ventilation network was formed and the effects of the gaps were calculated. If the gaps corresponding to 30% of the leakage are neglected then the calculated pressure is higher than the measured pressure, however, the results are in agreement if all gaps are taken into account.