SMOKE CONTROL PRACTICE IN MALAYSIA
Article by Ir TL Chen DL&F.ASHRAE 26/6/15
In Malaysia, the design, installation and maintenance of active smoke control systems are under the purview of the HVAC professionals and industry. Meanwhile, the legal requirements pertaining to the need for smoke control are regulated by the Fire & Rescue Department of Malaysia (Bomba) under the auspices of the Uniform Building By-Laws.
Bomba’s stringent requirements pertaining to fire protection installations are at par with and even exceed the best in the world. In terms of smoke control, Malaysia is the only country that requires any non fire compartmented occupancy exceeding 1,000 m2 to be provided with a smoke spill system.
Over the years, two Malaysian Standards on smoke control design have been published.
1) MS 1472: 1999 Code of Practice for Fire Precautions in the Design of Buildings – Smoke Control in Protected Escape Routes using Pressurization; and
2) MS 1780: 2005 Smoke Control System using Natural (Displacement) or Powered (Extraction) Ventilation
MS 1472: 1999
This standard was developed with reference to BS 5588: Part 4: 1978 ‘Fire precautions in the design of buildings: Part 4: Smoke Control in protected escape routes using pressurization’. It is certainly one of the oldest standards in the MS library that has not been revised. Early this year (2015), a working committee was finally appointed to commence revision of this standard. The committee comprises a MASHRAE rep and is chaired by the author.
This standard offers a different method for keeping protected escape routes clear of smoke by pressurizing these routes and so creating a pattern of airflow away from them. The objects of the 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 under all circumstances. It has however, certain advantages in as much as it offers greater flexibility of layout than other methods and in some cases reduced costs stemming from this flexibility.
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 standard.
Once inside a protected route, people in the 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 and 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 it consisting of hot gases less dense than the surrounding air;
b) The normal air movement (which may have nothing 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;
b) the wind, all buildings having some air leaks and wind action contributing to air movement through the leaks;
c) any mechanical air-handling system installed in the building.
Pressurization provides pressure differences that oppose and overcome those generated by the factors causing movement of the smoke. In pressurization, air is injected into the protected escape routes, i.e. Into staircases, lobbies or corridors, to raise their pressure slightly above the pressure in adjacent parts of the building. Consequently smoke or toxic gases will be unlikely to find their way into escape routes.
The use of the 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. The design criteria given in detail deal with the various ways in which `the escape of pressurized air can be arranged.
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 reilable and capable of functioning for a period correponding to the standard of fire resistance of the elements of structure in a building;
d) be simple and economic.
Some of the advantages that can be expected from the use of pressurization are:
a) staircases and lobbies need not be placed on external walls;
b) smoke shafts may not be required as a means of alternative ventilation;
c) it may be possible to omit some ‘smoke stop’ doors from escape routes;
d) the additional staircase considered necessary in calculating the number of staircases required in relation to the population density when other methods of smoke control are used may possibly be omitted;
e) conservation of energy.
MS 1472 deviates from referenced BS in the following specific areas to reflect current practices in Malaysia;
1) Local practice does not permit the pressurizing of the whole building unlike in the UK;
2) For pressurization of staircases, the allowance is for a single supply entry point to serve four storeys or fewer instead of three storeys or fewer;
3) The reverse stack effect (rather than stack effect) is taken into consideration in the design of pressurization of staircases for high rise buildings;
4) The allowance for leakage calculation for sheet metal ducting is stipulated at 10% and not 15%;
5) The period for testing the emergency operation of system is monthly instead of weekly;
6) Minimum egress velocity is standardised to 1.0 m/s.
MS 1780: 2005
Malaysia holds the distinction of being the first country in the world to publish a standard on smoke control by means of extraction or smoke spilling. All other countries merely have guides or practice notes on such requirement since smoke control is considered a very dynamic subject with research forever on-going.
The need for MS 1780 is in tandem with Malaysia’s stringent and pioneering regulations on smoke control system. The standard allows practitioners to follow a transparent means of designing to meet Bomba’s requirements and to eliminate as much ambiguity as possible.
The importance of smoke control is premised upon the fact that smoke obscures visibility and can also contribute to fatalities in a fire incident. It is therefore necessarily realised that occupant safety in a fire can be greatly improved by providing an efficient smoke control system. Moreover, such systems can limit property damage, both directly by reducing the spread of smoke, and indirectly by providing better visibility and thus easier access to the seat of the fire for fire fighters.
Smoke control is one of the tools, which the fire safety engineer may use to ensure adequate fire safety within a building. As such it should not be considered in isolation, but as an integral part of the total package of fire safety measures designed for the building. Thus the need for smoke extraction in any building should be designed in conjunction with the means of escape, compartmentation and active suppression systems.
This standard provides the fire size in terms of heat output and perimeter of fire for different types of occupancy to enable the designers to calculate the relevant smoke extraction quantum. It also stipulates the smoke clearance heights for lower and upper floors for both powered and natural smoke ventilation. Atrium smoke control by means of smoke reservoir principle is established for both sterile and non sterile tube atrium.
The standard permits engineered design solutions as well as performance based solutions through use of computational fluid dynamic simulations.
This pioneering standard has certainly proven its effectiveness and after a decade of use, a working committee (circa 2015) is now working on its revision for updates and to include the incorporation of jet fan ventilation system. Once again MASHRAE is represented in this committee chaired by the author.