FOCUS
Public/complex buildings
challenge in the integration of these protected routes within the existing building is focused on the interface at each level. In new buildings, the footprint of each
floor, layout of each floor and core design are generally uniform through the height of the building. But as a result of the different floor layouts in Manchester Town Hall, the layout of each protected route cannot be the same at every level. The design of each core is also bespoke for each level, which requires substantial coordination to enable the existing building to meet modern day requirements for fire rated egress routes and firefighting shafts.
Fire prevention
Preventing a fire from occurring is a key element in the protection of both property and life safety. In many heritage buildings, the fire risk is commonly associated with old utilities, electrical wiring and plant. At Manchester Town Hall, a number of the more recent fire events have had similar origins, including small fires starting in old light fittings. A substantial part of the proposed
refurbishment is focused on a complete overhaul of the building services. By bringing these services up to modern standards, the risk of fire through faulty components or wiring is reduced and provides an added benefit – the opportunity to install new fire safety systems. In order to provide an adequate level
of life safety to the public and staff, a number of active fire safety systems are proposed for Manchester Town Hall, including a new fire detection and alarm system, new emergency
24 JULY/AUGUST 2018
www.frmjournal.com
lighting and escape route signage, and new smoke ventilation. Integrating these systems into the existing fabric of the building remains a challenge and it is not likely that a ‘one size fits all’ approach will be appropriate. The proposed detection system is expected
to be a combination of point type detectors, aspirating systems and beam detection – the last two being used where there are particularly sensitive heritage spaces, or in large public spaces such as the central Great Hall. The system will operate on what is commonly referred to as a ‘double knock’, the main benefit of which is that if there is an erroneous detection, the system does not automatically sound an alarm resulting in the evacuation of a few thousand people. Instead, it provides a period for investigation during which, if an incident is confirmed – either manually by staff or automatically through activation of a second detector – the alarm will be sounded. If the investigation concludes an erroneous detection, the alarm sequence can be cancelled, minimising the disruption to the large number of staff and public within the building. A new fire alarm system is proposed for
Manchester Town Hall which will provide an audible alarm throughout the building, in addition to visual alerting beacons in accessible facilities and anywhere where lone working may occur. There are many merits in using a voice
alarm system for the audible alarm in a public building. These include not only the ability to broadcast different messages, as appropriate to the emergency, but also to decrease the overall evacuation time by encouraging people
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