Current examinations of car park industrial air systems have revealed some alarming shortcomings, especially in the application of jet fan systems. These failings vary from poor design with major areas of the car park left unventilated by designs which should control smoke in the event of fire but have no chance of doing so.
Popular belief is that due to the amount of time that jet fan systems have been around and the fact that they now represent around 95% of recent installations, people feel that it cannot be too difficult to design these systems themselves and then simply buy the fans. Even systems designed and fitted by supposed industry specialists have been found to be lacking in their effectiveness.
Many issues have been identified as lack of knowledge regarding fan installations or simply a misunderstanding of regulations. An example of a jet fan system installed and investigated involved, quite correctly, two axial main extract fans installed in parallel discharging into a common plenum; however they were installed without non-return dampers fitted to the fans. If one of these fans were to fail, the result would not only be in the loss of performance from the failed fan, but also severely reducing the effectiveness of second fans performance due to air short-circuiting through the failed fan.
Furthermore, there have been circumstances where the fire strategy has been inadvertently or deliberately disregarded. For example, the fire strategy of one project called for an enhanced smoke control system to guarantee that access lobbies were free of any smoke contamination in the case of a fire ever occurring in the car park. In actuality what was installed was an extremely rudimentary smoke clearance system which bore no resemblance to a smoke control system. The particularly worrying issue in this example is that this was missed by the client, the building control officer and consulting engineer; it was only recently discovered by the fire officer and we were called in.
How does this happen? Fundamentally due to cost, and a “design & build” culture in which the original objectives determined by the architect, consulting engineer and fire engineer have been disregarded or forgotten against a background of Value Engineering.
This is not to say there is anything wrong with Value Engineering when the original strategy and objectives are adhered and met; however these can and are easily overlooked and conveniently forgotten when the contractor, guided by an enthusiastic pseudo-specialist, is led to believe that tremendous savings can be made by cutting some corners. It can all seem highly believable when informed by a ‘specialist’ that the system is ‘code compliant’ and fully meets all the required building regulations, and this may very well be the case. However what has been ignored is the enhanced design specification agreed upon at the original design stage and against which relaxations were granted by building control regarding the requirement for sprinklers and the ventilation of access lobbies.
After a period of time, even be it only a few months, the error may be identified, at which stage the wonderful savings first purported become nothing but a drop in the ocean in comparison to the costs to correct the issue; these delays can not only delay the handover of the building but if the shortcomings are not identified, the safety and lives of the occupants of the building could be put in danger.
How can this be prevented in the future? It boils down to understanding how the original system design was developed and why. If the professed savings offered by alternative suppliers of specialist systems sound too good to be true, then it should be a warning sign and more than likely is. In this case, discussions with the parties involved in developing the original system design should be consulted to gain a comprehensive understanding of the design objectives that must be obtained and system requirements which must be met.
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