BS 7346-4-2003 Components for smoke and heat control systems - Functional recommendations and calculation methods for smoke and heat exhaust ventilation systems employing steady-st.pdf

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1、BRITISH STANDARD BS 7346-4:2003 Components for smoke and heat control systems Part 4: Functional recommendations and calculation methods for smoke and heat exhaust ventilation systems, employing steady-state design fires Code of practice ICS 13.220.20 BS 7346-4:2003 This British Standsrd was publish

2、ed under the authority of the Standards Policy and Strategy Committee on 29 August 2003 BSI 29 August 2003 The following BSI references relate to the work on this British Standard Committee reference FSH/25 Draft for comment 00/541350 DC ISBN 0 580 42233 X Committees responsible for this British Sta

3、ndard The preparation of this British Standard was entrusted to Technical Committee FSH/25, Smoke, heat control systems and components, upon which the following bodies were represented: Association of Roof Light Manufacturers BRE/LPC Laboratories British Blind and Shutter Association Building Servic

4、es Research and Information Consumer Policy Committee of BSI Fire Resistant Glass and Glazing Federation HEVAC Association Institution of Fire Engineers London Fire and Emergency Planning Authority OPDM Building Regulation Division ODPM Office of the Deputy Prime Minister Smoke Vent Association Stee

5、l Window Association Co-opted members Amendments issued since publication Amd. No. Date CommentsBS 7346-4:2003 BSI 29 August 2003 i Contents Page Committees responsible Inside front cover Foreword ii 0 Introduction 1 1S c o p e 5 2 Normative references 5 3 Terms, definitions, symbols and units 6 4 G

6、eneral recommendations 14 5 Calculation procedures 19 6 Performance recommendations 22 7 Interaction with other fire protection systems and other building systems 40 Annex A (informative) Default value heat release rates 44 Annex B (informative) The plume rising directly from the fire into a smoke r

7、eservoir 44 Annex C (informative) The flow of hot smoky gases out of a fire-room into an adjacent space 47 Annex D (informative) The flow of hot smoky gases under a soffit projecting beyond a fire-rooms opening or window 51 Annex E (informative) The spill plume 56 Annex F (informative) The smoke res

8、ervoir and ventilators 56 Annex G (informative) The influence of zones of overpressure and/or zones of suction upon a SHEVS 60 Annex H (informative) Deflection of free-hanging smoke barriers 63 Annex I (informative) Plenum chamber 67 Annex J (informative) Atrium depressurization 69 Annex K (informat

9、ive) The interaction of sprinklers, a SHEVS and fire-fighting actions 79 Annex L (informative) The effect of a buoyant layer on the minimum pressure recommended for a pressure differential system 80 Bibliography 83 Figure 1 Design regions for a single-volume space 19 Figure 2 Design regions for a sp

10、ace where there is a spill plume 21 Figure 3a) Adhered plume 28 Figure 3b) Free plume 29 Figure 4a) Deep balcony projection 30 Figure 4b) Shallow balcony projection 31 Figure 5 Flow resistance through openings in an atrium 39 Figure 6 Early (or premature) stratification of smoke 41 Figure B.1 Limiti

11、ng size of a cellular room 45 Figure B.2 Smoke ventilation in a single-storey mall 47 Figure C.1 Flow out of an opening with high balcony 48 Figure C.2 Flow out of an opening with downstand and projecting balcony 49 Figure D.1 Smoke spreading sideways beneath a projecting canopy or balcony 52 Figure

12、 D.2 Smoke confined to a compact spill plume by channelling screens 53 Figure D.3 Slot exhaust 55 Figure F.1 Use of smoke transfer ducts in otherwise stagnant regions 59BS 7346-4:2003 ii BSI 29 August 2003 Page Figure G.1 Zones of overpressure on a roof with an outstanding structure 60 Figure G.2 As

13、sessment of h stin case of a roof with an outstanding structure and a parapet 61 Figure G.3 Zones of suctions affecting the location of inlet openings 62 Figure H.1 Forces acting on a deflected smoke barrier 64 Figure H.2 Forces acting on a deflecting smoke barrier closing an opening 66 Figure I.1 P

14、lenum chamber 68 Figure J.1 Neutral pressure plane throughflow ventilation 70 Figure J.2 Neutral pressure plane exhaust larger than inlet 71 Figure J.3 Neutral pressure plane above highest leaky storey 72 Figure J.4 Principles of hybrid smoke ventilation system mass flow-based 76 Figure J.5 Principl

15、es of hybrid smoke ventilation system temperature-based 78 Figure L.1 The neutral pressure plane and layer buoyant pressure 81 Table 1 Default values of design fires 24 Table 2 Minimum clear height above escape routes 25 Table 3 Convective heat flux at the room opening 26BS 7346-4:2003 BSI 29 August

16、 2003 iii Foreword This part of BS 7346 has been prepared by Technical Committee FSH/25. The other parts comprising BS 7346 are: Part 1: Specification for natural smoke and heat exhaust ventilators; Part 2: Specification for powered smoke and heat exhaust ventilators; Part 3: Specification for smoke

17、 curtains. The above three standards are eventually to be replaced by EN 12101, Smoke and heat control systems, consisting of the following parts: Part 1: Specification for smoke barriers Recommendations, test methods; Part 2: Specification for natural smoke and heat exhaust ventilators; Part 3: Spe

18、cification for powered smoke and heat exhaust ventilators; Part 4: Smoke and heat control installations Kits; Part 6: Functional requirements and calculation methods, components, installation and testing procedures for pressure differential smoke control systems; Part 7: Smoke control ducts; Part 8:

19、 Smoke control dampers; Part 9: Power supply equipment; Part 10: Control equipment. EN 12101 forms part of a series of European Standards, which are planned to cover: CO 2systems (EN 12094); sprinkler systems (EN 12259); powder systems (BS EN 12416); explosion protection systems (BS EN 26184); foam

20、systems (pr EN 13565); hydrant and hose reel systems (BS EN 671); semi-rigid hose systems (EN 694). As a code of practice, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that cl

21、aims of compliance are not misleading. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This docum

22、ent comprises a front cover, an inside front cover, pages i to iv, pages 1 to 83 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.iv blankBS 7346-4:2003 BSI 29 August 2003 1 0 Introduction 0.1 General introduction Smoke and heat exhaus

23、t ventilation systems (SHEVS) create a smoke free layer above a floor by removing smoke. They can, therefore, improve conditions to allow the safe escape and/or rescue of people and animals, to protect property and to permit a fire to be fought while still in its early stages. Ventilation systems fo

24、r smoke removal also serve simultaneously for heat exhaust and can exhaust hot gases released by a fire in the developing stage. The use of such systems to create smoke free areas beneath a buoyant smoke layer has become widespread. Their value in assisting in the evacuation of people from buildings

25、, reducing fire damage and financial loss by preventing smoke logging, facilitating fire-fighting, reducing roof temperatures and retarding the lateral spread of fire is firmly established. For these benefits to be realised it is crucial that smoke and heat exhaust ventilators operate fully and reli

26、ably whenever called upon to do so during their installed life. Components for a SHEVS need be installed as part of a properly designed smoke and heat exhaust system. Natural SHEVS operate on the basis of the thermal buoyancy of the gases produced by a fire. The performance of these installations de

27、pends, for example, on: the temperature of the smoke; the fire size; the aerodynamic free area of the ventilators, or the volume of smoke exhausted by powered ventilators; the wind influence; the size, geometry and location of the inlet air openings; the size, geometry and location of smoke reservoi

28、rs; the time of actuation; the arrangements and dimensions of the building. Ideally the design fire upon which calculations are based shows the physical size and heat output of the fire changing with time in a realistic manner, allowing the growing threat to occupants, property and fire-fighters to

29、be calculated as time progresses. Such time-based calculations of the time-to-danger usually have to be compared with separate assessments of the time recommended for safe evacuation of occupants of the building or of the time recommended for initiation of successful fire-fighting. These latter asse

30、ssment procedures fall outside the scope of this British Standard, although it is anticipated to supplement this standard with design procedures for time-dependant fires in the future. In these calculations fire growth curves are selected that are appropriate to the precise circumstances of the buil

31、ding occupancies, fuel arrangements and sprinkler performance, where appropriate. Where such information is available, these calculations are conducted on a case-by-case basis using recommended fire safety engineering procedures. Even where such an approach is adopted, appropriate performance recomm

32、endations, e.g. minimum clear height, external influences, can be drawn from this British Standard. NOTE BS 7974 describes the application of fire safety engineering principles to the design of buildings. Where such time-based calculations are not feasible, it is possible to use a simpler procedure

33、based on the largest size a fire is reasonably likely to reach in the circumstances. This time-independent or steady-state design is not to be confused with steady fires, which achieve full size instantly and then burn steadily. Rather the procedure assumes that a SHEVS that is able to cope with the

34、 largest fire can also cope with the (usually earlier) smaller stages of the fire. In practice, it is much easier to assess the largest reasonably likely size of fire than to assess the growth rate of that fire.BS 7346-4:2003 2 BSI 29 August 2003 0.2 Smoke exhaust ventilation design philosophies 0.2

35、.1 Protection of means of escape (life safety) A common approach to protect a means of escape is to achieve a smoke-free height beneath a thermally buoyant smoke layer below a ceiling. A SHEVS uses this principle to allow the continued use of escape routes that are in the same space as the fire, e.g

36、. within enclosed shopping malls and many atria. The rate of smoke exhaust (using either natural smoke exhaust ventilators or powered smoke exhaust ventilators) is calculated to keep the smoke at a safe height above the heads of people using the escape routes, and to keep the radiated heat from the

37、smoke layer at a low enough value to allow the escape routes to be used freely, even while the fire is still burning. 0.2.2 Temperature control Where the height of clear air beneath the thermally buoyant smoke layer is not a critical design parameter, it is possible to use the calculation procedures

38、 in 0.2.1 in a different way. The rate of smoke exhaust can be designed to achieve (for a specified size of fire) a particular value for the temperature of the gases in the buoyant layer. This allows the use of materials that would otherwise be damaged by the hot gases. A typical example is where an

39、 atrium faade has glazing that is not fire-resisting, but which is known to be able to survive gas temperatures up to a specified value. The use of a temperature control SHEVS in such a case could, for example, allow the adoption of a phased evacuation strategy from higher storeys separated from the

40、 atrium only by such glazing. 0.2.3 Assisting the fire-fighting operation In order for fire-fighters to deal successfully with a fire in a building, it is first necessary for them to drive their fire appliances to entrances that give them access to the interior of the building. They then need to tra

41、nsport themselves and their equipment from this point to the scene of the fire. In extensive and multi-storey complex buildings this can be a long process and involve travel to upper or lower levels. Even in single-storey buildings the fire-fighters within the building need, amongst other things, an

42、 adequate supply of water at sufficient pressure to enable them to deal with the fire. The presence of heat and smoke can seriously hamper and delay fire-fighters efforts to effect rescues and carry out fire-fighting operations. The provision of SHEVS to assist means of escape or to protect property

43、 aids fire-fighting. It is possible to design a SHEVS similar to that described in 0.2.1 to provide fire-fighters with a clear air region below the buoyant smoke layer, to make it easier and quicker for them to find and to fight the fire. Temperature control designs are of less benefit. This documen

44、t does not include any functional recommendations for key design parameters where the primary purpose of the SHEVS is to assist fire-fighting. Such functional recommendations need to be agreed by the fire service responsible for the building in question. However, the calculation procedures set out i

45、n the annexes of this document can be used to design the SHEVS to meet whatever recommendations have been agreed. 0.2.4 Property protection Smoke exhaust ventilation cannot by itself prevent fires growing larger but it does guarantee that a fire in a ventilated space has a continuing supply of oxyge

46、n to keep growing. It follows that smoke exhaust ventilation can only protect property by allowing active intervention by the fire services to be quicker and more effective. Property protection is therefore regarded as a special case of 0.2.3. Depending on the materials present, a property protectio

47、n design philosophy can be based on the need to maintain the hot buoyant smoke layer above sensitive materials (similar in principle to 0.2.1), or the need to maintain the smoke layer below a critical temperature (similar to 0.2.2). In either case, the functional recommendations for key parameters o

48、n which the design is based need not be the same as where the primary purpose is life safety and will depend on the circumstances applying in each case. These key functional recommendations need to be agreed with all relevant interested parties. The calculation procedures in the annexes of this stan

49、dard can be used to design the SHEVS.BS 7346-4:2003 BSI 29 August 2003 3 0.2.5 Depressurization Where a smoke layer is very deep, and storeys adjacent to the layer are linked to it by small openings, e.g. door cracks or small ventilation grilles in walls, it can be possible to prevent the passage of smoke through the small openings by reducing the pressure of the gases in th