Product Details This part of BS provides guidance on the incorporation of one or more atria into new and existing buildings. The primary objective of the code is to ensure that the incorporation of an atrium into a building does not present an increased risk to life as a result of fire and smoke spread. This code is concerned only with those additional measures that may be required to compensate for any increased risk resulting from the inclusion of an atrium within a building. It is not intended to provide a fire-engineered solution for any particular design. The principles presented in this standard are applicable to all building types containing atria other than: prisons or other buildings intended for the confinement of persons; auditoria in theatres or similar places of entertainment, for which guidance is given in BS ; malls in shopping complexes for which guidance is given in BS
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In addition to the existing BS The objects of this code are to state general principles and to give both planning and technical data concerning pressurization of protected escape routes. Pressurization is one of several methods of smoke control in buildings in the event of fire and it is not suggested that it is the only effective method in all circumstances.
It has however certain advantages inasmuch as it offers greater flexibility of layout than other methods and in some cases reduced costs stemmin g from this flexibility. Designers will need to offer the system described in this code to the building control authority as an alternative to the natural ventilation that may be required by specific legislation.
Protected escape routes may include corridors, lobbies, staircases and other communication spaces connecting to a final exit. Unprotected routes include spaces within rooms or open storeys and corridors where travel distances apply.
The travel distances as specified in other codes or regulations should not be modified because smoke control is employed as described in this code. Once inside a protected route, people in a building should be able to make their way to a final exit and safety in the open air.
It is smoke and toxic gases, rather than flame, that will in the first instance inhibit this movement an d the exclusion of smoke and gases from the protected routes is thus of great importance. In normal fire-prevention design the intention always will be to confine the fire within a fire compartment and, although this may be effective in limiting the spread of fire, smoke will readily spread to adjacent spaces through the various leakage openings that occur in the compartment enclosure, such as cracks, openings around pipes, ducts, airflow grilles and doors.
In good building practice the leakage at some of these points will be minimized but it is not generally possible to seal them completely. There are two main factors that determine the movement of smoke arising from a fire in a building. These are: a the mobility of smoke that results from its consist ing of hot gases less dense than the surrounding air; b the normal air movement which may have nothin g to do with the fire that can carry smoke, sometimes slowly, sometimes quickly, to all parts of the building.
Air movement is itself controlled by: a the stack effect see 3. In pressurization, air is injected into the protected escape routes, i. Consequently smoke or toxic gases will be unlikely to find their way into escape routes. The use of a system to extract air from spaces that are pressurized is very strongly deprecated because it will render the maintenance of the required pressure in the escape routes extremely difficult.
It is necessary to determine not only where the fresh air supply for pressurization is to be introduced into a building but also where that fresh air will leak out and what paths it will take in the process. The aim will be to establish a pressure gradient and thus an airflow pattern with the protected escape routes at the highest pressure and the pressure progressively decreasing in areas remote from the escape routes. A pressurization system for smoke control should: a give positive smoke control in the protected escape routes; b be readily available when a fire starts; c be reliable and capable of functioning for a period corresponding to the standard of fire resistance of the elements of structure in a building; d be simple and economic.
Diagrams that accompany the text in this code are intended only to clarify points made in the text. It should not be assumed that the arrangements shown are more satisfactory than others that may be devised. Consultation with the building control authority at an early stage is recommended, to check not only that proposals for means of escape are satisfactory but also that other building regulations, concerned for example with ventilation of parts of the building for public health purposes, are satisfied.
This code does not contain all the necessary information for the satisfactory design of a pressurization scheme, which should be undertaken by a competent person. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 38, an inside back cover and a back cover.
This standard has been updated see copyright date and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. The code is intended to apply to new buildings, t hough there is no reason why the principles should not be used when existing buildings are to be altered or adapt ed.
The principles stated in the code may be used for other occupancies and purpose groups where the fundamental aim is to keep the protected escape route clear of products of combustion. This code is not intended to apply to shopping malls and town centre redevelopments. These are t he staircase s , the lobbies and in some cases the corridors. This is called a single-stage system. See 5. Pressurizing staircase s only. The simple lobby should be unventilated, in which case it will be automatically pressurized by the air flowing out of the staircase.
Figure 1 shows examples of pressurized staircases leading into simple lobbies. The resulting pressurization of the lobbies is indicated, as also is the effect of an open lobby door. During a fire emergency all protected staircases interconnected by lobbies, corridors or accommodation areas should be simultaneously pressurized. Pressurizing the staircase s and all or part of the horizontal route 4.
In every building in which each floor has a horizontal component of the protected escape route other than the simple lobby mentioned in 4. This arrangement carries the protection right up to the door leading into the accommodat ion area in which a fire might occur.
Additionally, the effect of an open door on the pressurization levels is largely localized on the floor concerned. If a lobby separating the staircase from the accommodation is other than a simple lobby, this lobby should be pressurized independently of the staircase, i.
The lobby pressure should be equal to or slightly below the pressure in the staircase but not more than 5 Pa below. Figure 3 shows an example of independently pressurizing staircase and lift lobby and indicates the effect of an open door.
If the lobby opens into a corridor of substantial construction i. To do this an independent air supply should be provided to the corridor and the pressure should be equal to or slightly below that in the associated lobby, but not more than 5 Pa below. There are difficulties associated with this extension of the pressurization. If the corridor has many doors or other leakage paths the air supply needed will be large, each door should be self-closing and each unpressurized space opening onto the corridor should have adequate leakage to the outside air as recommended in 5.
In some buildings it may be found necessary, perhaps for constructional reasons such as difficulty in arranging the required ductwork for independent pressurization to allow the staircase to be pressurized by the air that leaks into it from the associated pressurized lobbies or corridors. If properly designed this can be a satisfactory method but in some cases it may be found that the total air supply needed for pressurizing the lobbies only may be greater than that needed if the staircase and lobbies are independently pressurized.
In this method the staircase should not be permanently ventilated except by any opening shown to be necessary by the calculation for the open-door condition dealt with in 5. Designs have been suggested for a scheme in which pressure differentials are not developed inside the building but air is introduced in such a way that the whole building is raised to a pressure in excess of that obtaining outside the building. In the event of fire, airflows are set up in opposition to the smoke flow by opening vents on the fire floor.
This system has been suggested for buildings in which the internal divisions are so leaky that pressurizing particular spaces such as staircases or lobbies is not possible. In the UK there is no experience with this method and it is suggested that, unless there are over-riding reasons for its adoption in a special case, it does not constitute a satisfactory method.
To design this type of system the details, including location, of the air leakage from the external wall are required. If this leakage is appreciable as suggested by some of the information available , a wastefully high amount of pressurizing air is required. Venting elsewhere can cause smoke to spread to other parts of the building. In a building, particularly a large building, there may be several pressurized spaces. This will apply t o many buildings.
It has been explained that the purpose of a pressurization system is to establish an airflow condition in the building that will prevent the smoke from a fire moving towards or past the escape route doors. This is achieved by maintaining the escape routes at an excess pressure by providing them with a mechanically driven constant supply of fresh air, and, additionally, by providing for th is air to leak out of the building at identified places in or near external walls that are as far as possible from the escape route doors.
It is therefore preferable that the airflow pattern est ablished in the building by the normal air conditioning system should also be away from the escape route entrance, with the vitiated air being removed for exhaust or recirculation at points remote from the escape route entrances.
If the pressurization system is two-stage, i. When the pressurization system is single-stage, i. An air conditioning system that uses the corridors or the false ceiling of a corridor as the exhaust plenum for the vitiated air should not be used in conjunction with a pressurization system unless special arrangements are made for closing off the whole exhaust system in case of fire.
In any case, an air conditioning system that could encourage smoke to enter the corridors is not favoured for fire safety reasons even if there is no pressurization in the building. It is suggested that the normal air conditioning system and the pressurization system should be treated as an integral whole when design calculations are carried out. This will certainly be necessary when the pressurization is two-stage, i.
When the emergency pressurization is brought into action the following changes in the normal air conditioning system should be made. The signal to initiate all these changes in the operation of the air conditioning system should come from the same source as that which operates the emergency pressurization.
The use of a smoke detector in the air conditioning ductwork should not be relied on for this purpose because of the dilution of the smoke t hat will occur when several floors are served by the same system. This could cause a delay in operating the necessary adjustment to the air conditioning system in case of fire. The criterion is to establish in the building a pressure gradient patt ern that will always ensure that smoke moves away from the escape route. To do this the escape route is maintained at an excess pressure and adequate air leakage has to be provided from the accommodation areas.
These are established by maintaining a continuous supply of fresh air, fed by mechanical means into the pressurized space. This is designed by first identifying the leakage paths see 5.
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BS 5588-4-1978 Fire Precautions 3
In addition to the existing BS The objects of this code are to state general principles and to give both planning and technical data concerning pressurization of protected escape routes. Pressurization is one of several methods of smoke control in buildings in the event of fire and it is not suggested that it is the only effective method in all circumstances. It has however certain advantages inasmuch as it offers greater flexibility of layout than other methods and in some cases reduced costs stemmin g from this flexibility. Designers will need to offer the system described in this code to the building control authority as an alternative to the natural ventilation that may be required by specific legislation.