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Automatic fire door actuation devices are becomming more popular as a way of allowing people to move more freely, while ensuring door closure in the event of a fire alarm. Exclusively for FSE Steven Daws previews a new code of practice for these solutions.
Nowadays, it is commonplace for self-closing fire resisting doors to be held open by devices linked to a fire detection and alarm system. These will close the doors automatically in the event of fire. This arrangement allows freedom of access and movement under normal circumstances, but ensures that doors are closed when most needed – to control the spread of fire and smoke through a building. Indeed, the installation of these devices is so widespread that it might surprise you to know that, to date, there have been no national standards covering how they should be actuated. While there are British/European standards for the devices themselves, there is no code of practice with recommendations governing their use and, in particular, the design and installation of the interface with the fire detection and fire alarm system.
In view of this, BSI is publishing BS 7273-4 Code of practice for the operation of fire protection measures Part 4: Actuation of release mechanisms for doors. This new code of practice will not only cover the interface between fire detection and alarm systems and devices to hold open self-closing doors, but also governs the interface with devices on doors that are required to open in the event of a fire i.e. devices that secure doors on means of escape, for example, magnetically held and solenoid-operated locks, and devices that control powered sliding doors on escape routes, for example, those that form final exits from buildings.
You might wonder why a standard is needed. After all, are not such devices simply arranged to ‘fail safe’ so that, for example, in the event of power failure, held open doors close while secured/powered sliding door release to open? Well, no, this is not necessarily the case in practice. There may previously have been a perception that these devices would fail safe, but the way in which these devices have been interfaced with fire detection and fire alarm systems in the past would not always ensure that this would be the case. Fundamental to the standard is, therefore, the definition of ‘fail safe’, and the specification of the criteria for fail safe operation.
In fact, the standard goes further. It defines three different categories of actuation – A, B, and C – each of which has a set of criteria for fail safe operation under defined conditions. Category A is the most onerous. It requires fail safe operation even when there is loss of both the mains and standby power supplies to the fire detection and fire alarm system, as well as various fault conditions on the wiring. Category B is less onerous in that not all of the fault conditions specified for Category A actuation would close held open doors, or release secure or powered sliding doors to open. Category C actuation addresses situations where there is no direct communications path between the fire alarm control and indicating equipment and the release mechanism. An example of this is actuation of the release mechanism facilitated by other control, or similar, equipment (such as an access control system or an electrically controlled hold-open system).
There is tentative guidance on the use of these different categories of actuation, and, in particular, on when Category A might be applied. However, this standard does not state where and when devices to open, unlock and release doors in the event of fire should be used. Indeed, it is not intended to imply that these devices will always be acceptable in all circumstances and in all premises. It is important to understand that the acceptability, under legislation, of the use of these devices will often need to be determined by means of a fire risk assessment carried out by a competent person.
In addition to addressing the applications for mechanisms for unlocking and releasing doors and defining categories of actuation, the standard also covers the methods of actuation (e.g. manual and automatic), power supplies and the monitoring, integrity and reliability of arrangements in which release mechanisms are actuated by a fire detection and fire alarm system. There are clearly circumstances in which devices on secure doors should not release immediately on activation of the fire detection and fire alarm system. These include prisons and mental health units. However, in most situations, it will be appropriate to release the doors to open when the fire alarm is sounded, and also for held-open doors to close immediately.
It will also be appropriate, in most circumstances, for there to be manual controls to enable the release of secure doors – the ubiquitous green ‘break glass’ override control. But again there will be some, albeit restricted, exceptions. Manual controls are also recommended alongside powered sliding doors to release them to open. Manual controls to close held open doors may be appropriate, for example as a means to close all doors at night in residential situations. However, it is not necessary for compliance with the standard that these be provided by every door, but, there may be benefits in doing this. It is, nevertheless, recognised that there may be a central control to manually close the doors throughout the building. However, there are risks associated with operating a central control, and a suitable warning sign is recommended in these circumstances.
As well as addressing arrangements in which the fire detection and fire alarm system is interfaced to release mechanisms by means of wiring, the standard also covers interfaces that incorporate acoustic coupling and radio transmission. Acoustically actuated systems have been in use for some time, but have not always been readily accepted by some enforcing authorities. Although acoustically actuated systems cannot be used for applications requiring Category A actuation, there are many applications for which they will be suitable and should be accepted. Since no wiring is needed between any part of the fire detection and alarm system and the release mechanism, the release mechanisms can be much easier, quicker and cheaper to install. Disruption of normal activities during installation is minimised, and additional release mechanisms can easily be added at a later date, to cater for modifications or extensions to the building. The same benefits apply to radio actuated systems. Again, there are also special considerations in the use of radio actuated systems, and it is important that these are taken into account when deciding upon the suitability of such systems for a particular application.
Possibly one of the most significant areas covered by the standard is the extent of automatic fire detection recommended for situations in which devices to release hold-open doors are used. The need for automatic smoke detectors to be provided in close proximity to the doors is well recognised, but often this has been satisfied by simply providing a detector on each side of the door. Although not stated in any British Standard, a well known rule of thumb has been to place each detector within 1.5m of the door. There is, however, the potential for the fire to go undetected and the doors to fail to close, if detectors are only provided next to the doors. In practice, much more widespread detection is necessary. As a minimum, it will be necessary to specify a Category M/L5 system as defined in BS 5839-1. A series of diagrams is included in the standard to clarify the extent of detection necessary under a variety of different circumstances.
While the introduction of this standard will, undoubtedly, have a major impact on industry practice, it has been drafted in close consultation of all those affected, including manufacturers, suppliers and installers. It is hoped that, with the introduction of BS 7273-4, a common approach will be adopted by enforcing authorities and others in specifying their requirements, something which can only aid the industry in meeting its obligations to provide safe and effective measures to protect people and buildings in the event of fire.
Steven Daws is a consultant at C S Todd & Associates. He is chairman of the BSI fire detection and alarm systems sub-committee responsible for standards addressing the automatic operation of fire protection measures.