As one door opens...
Although it was first introduced in 2007, the 2015 revision of BS 7273-4 has brought the subject of release mechanisms for fire doors into sharp focus. Simon Foulkes, Product Owner at Gent by Honeywell, examines this revised code of practice and explains why more attention should be given to this important subject.
It stands to reason that the prompt evacuation of a burning building requires as few obstacles and obstructions as possible. Similarly, restricting the spread of fire and heat in such a situation relies upon the use of well-engineered fire doors that can be reliably closed in the event of a fire. Balance this with the need to conveniently use the building in normal operation and you can potentially have conflicting priorities. Control of doors within a building by the fire detection system has been commonplace for many years. However if fire doors are left open or exits remain locked this could lead to potentially disastrous consequences.
BSI’s BS 7273-4:2015 Code of Practice for the operation of fire protection measures – Part 4: Actuation of release mechanisms for doors, to give it it’s full title, is the latest revision of an eight year old standard, which focuses largely on the control arrangements for actuation of mechanisms that unlock, release or open doors in the event of fire. It covers recommendations for the interface between fire detection and alarm systems, as well as equipment not covered in any other standards.
Developed in association with representatives of the Fire Industry and other relevant bodies including manufacturers, suppliers and installers, those using this revised code of practice will be able to better understand how modern technology can be used to increase a building’s safety by interfacing it with fire doors and secured fire exits.
One of the key reasons behind the standard was to ensure that door management systems for doors critical to the safe management of a building in a fire situation must be fail safe such that the protection of the building is not impacted if for any reason the automatic control is compromised. If the guidelines are not followed it is likely that the fire door provision fails to satisfy the fire risk assessment. It is fair to say that since its original introduction the standard has been largely ignored apart for a few isolated cases of best practice.
The 2015 update of BS 7273-4 addresses some of the reasons for its lack of uptake clarifying the classification of the category of installation as well as when they should be used. The three categories of actuation – A (critical), B (standard) and C (indirect) – define the circumstances under which the control mechanisms should be “fail safe” depending on the risk associated with the door in each location. If the listed faults occur in either the door management system, the fire detection system, or the interconnection between the two, the system should perform as it would in the event of a fire and release the doors.
Category A – the most stringent – is to be applied for the highest risk situations, requiring fail safe operation when the cabling forming the communication path is broken, and when there are faults or disconnections that prevent the operation of the mechanism in a fire. Only a very few of the more intelligent systems can identify whether for instance a fault on a single detector will impact the operation of the door release system. A system that cannot, must release all doors in a building for every single fault on the control panel. Category B and C applications should both fail safe when the Critical Signal Path is interrupted by a short or open circuit. Category C applications require additional consideration as they apply when the fire system connects to the release system indirectly, for example via an access control system. Designers must ensure that the controller itself is also failsafe.
The guidance in Annex A of BS 7273-4 is now normative which means that if control of doors is performed by a fire detection system the requirements of the category must be met. For example, selecting a Category A solution must be considered for premises used by the public such as shops, theatres and public transport, as well as schools, hotels and care homes. However, it should be remembered that this type of system might be inappropriate in certain environments such as banks, hospitals and prisons, due to security issues, where doors could be held open to allow access to people who should have restricted movement.
Modern buildings are complex environments and there can be no ‘one size fits all’ approach to configuring a BS 7273-4:2015 compliant system. Fire doors and exits should be considered individually and, in order to ensure greater compliance with this important standard, life safety solution manufacturers are developing ‘intelligent’ systems that use algorithms that can understand the layout of a building and how to manage door opening and closing in particular scenarios thus avoiding the need to compromise on the convenience such door control is intended to achieve.
BS 7273-4:2015 will not only help to clarify the expectations of users and match it to the technology available, but it will also give fire safety enforcers defined criteria for fail safe operation. This will encourage a uniform approach by enforcing authorities and others in specifying objectives that ensure that people, property and assets are protected as well as they possibly can be in the event of a fire.
Published March 2016