Smoke Ventilation in Large Spaces

摘要

The study presented in the paper is focused on the problem of fire smoke evacuation via roof-mounted vents and fans along with working ordinary ventilation systems. Resulting pressure in a space in case of a fire is effected by different pressures due to buoyancy, thermal expansion of indoor air and wind pressure on the building. The combination of wind pressure on building and airtightness of the building along with opening of doors and/or windows in the walls and smoke vents on the roof can result in great variations of pressure. Furthermore, pressure balance will of course be influenced by operating an ordinary ventilation system. In order to evaluate indoor pressure under different circumstances the equivalent indoor wind factor **_i was established and an equation along with interval reducing method for its calculation are shown. Evaluation of the industrial and large spaces' airtighteness built at different times shows a great variation of data. Swedish construction traditions and airtightness requirements differ from those in the US A. For the purpose of this study the size of air leakage paths for Swedish buildings is determined by the requirements in the Swedish Building Regulations, i.e. air leakage is assumed to be 6 m~3/h, m~2 relating to the area of the building's envelope. The more complicated cases with wind effected roofs along with different pressures in the place when burning is analysed with the help of the computer program PFS.