smoke extraction

Topics: Shopping mall, Mass flow rate, Smoke Pages: 28 (10885 words) Published: October 12, 2013
Name: Leung Chun Wai
Student no.: G20554292
Topic: (NT3048) Smoke extraction design for large space such as atrium 1. INTRODUCTION
Atrium inside a building is an old architectural concept for about two thousand years. This concept has been developed and extended to modern buildings. Current trend of atrium design provides an ‘ideal’ external environment to the occupants with a large undivided space. The major problem for fires in atrium is hot and toxic gases accumulating and go down in the atrium, spreading throughout the atrium, and affecting escape routes, even there is no fire. Generally, atrium design is classified into three types which are cubic, flat and high [1, 2]. Cubic and flat atria have been widely applied in U.K. and Europe. For tall atria, it can be commonly found in Hong Kong and U.S.A.. The objective of this paper is to evaluate the performance of smoke exhaust system inside a tall atrium and develop such a ‘fire engineering’ approach, which can underpin a simple guide for engineers in the smoke management for tall atrium. This Report is intended to assist designers of smoke ventilation systems in enclosed shopping complexes. Most of the methods advocated are the outcome of research into smoke control by smoke ventilation at the Fire Research Station, but also take into account the recommendations1 of the Working Party on fire precautions in town centre redevelopment, as well as experience gained and ideas developed whilst the authors and their colleagues have discussed many proposed schemes with interested parties. The primary purpose of this Report is to summarise the design advice available from the Fire Research Station at the time of its preparation, in a readily usable form. As such, the Report is neither a detailed engineering manual nor is it a scientific review article. Perhaps most important of all, it is not a summary of the totality of approaches possible. New methods such as those based upon computational fluid dynamics, will be developed as time passes and there will always be special cases where existing alternative methods can be adopted. At peak times a shopping centre can be occupied by thousands of people, and some larger centres by more than a hundred thousand. A typical centre may comprise many individual shop units opening onto a common mall. Although the individual units may be separated from each other by a dividing wall of fireresisting construction, usually the shop is either open fronted or only separated from the mall by a glass shop front. This means that the public areas of the entire centre can be effectively undivided. Means of escape from within each shop unit will, in general, be specified (eg BS 5588 Part 22) in the same way as for shops which are not part of an enclosed complex. This means that escape from within the shops is specified as if the mall were as much a place of safety as the usual open-sky street. Unfortunately, the mall is a street with a roof, and so cannot be regarded as being as inherently safe as an open-topped street. People escaping from a shop into a mall will still need to travel along the mall before exiting to a true place of safety. It follows that the mall constitutes an additional stage to the escape route, which needs to be protected from the effects of fire and smoke. Ideally, it should approach the same level of safety as a street for as long as people need to escape through it — even if smoke enters the mall from the shop on fire. Details of means of escape provisions for the malls can be found elsewhere1. A shopping complex is a public building and the occupants will be a cross section of the community including the elderly, children and the disabled. They will not necessarily be familiar with the building, or perhaps more importantly, with all the escape routes that might be provided for them. In many types of building it is widely recognised that people will commonly try to escape by the same route they had used to enter the premises...
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