Public/complex buildings


to begin to evacuate sooner than is typically experienced with a standard tonal alarm. Conversely, designing a voice alarm system


to suit the existing town hall presents many intelligibility and audibility challenges, that arise due to large open spaces and sound reflective surfaces, as is commonly experienced in rail stations and airports. This reverberation of sound around the town hall is likely to limit the intelligibility of the voice alarm message, to the extent that the benefit gained over a standard tonal alarm is lost. To continue the provision of varied messaging to occupants in the event of an emergency, a number of alternative systems are also being explored including active signage and variable signage using TV screens or room information screens. In the future, it is quite likely that building management systems will be able to provide emergency information directly to occupants’ phones. In non public buildings, this is relatively straightforward to implement, as occupants are regularly present in the building, and staff inductions and fire drills can be used to administer a mobile based messaging system. For public buildings, this form of messaging


is more likely to piggyback off public information apps for the building. In the context of public buildings, it could be using information apps to navigate through an airport, or for heritage buildings, apps designed to help the public interact with the history around them. Emergency messaging coverage through


mobile technology cannot, however, be guaranteed in a public building, due either to individuals not having a suitable mobile device or choosing not to subscribe to the service. For a number of people, however, it can act as a useful source of ancillary information.


When fire occurs Some way to go


Although fire prevention is always the starting point of fire safety, in the event of a fire starting it is important to either suppress or contain it to the smallest area possible. Within Manchester Town Hall the integration of a sprinkler system conflicts substantially with the heritage fabric of the building. In the event of a fire occurring, the focus is


therefore to minimise fire and smoke spread to the greatest extent possible. This is both to minimise the impact on the building and its assets, and to minimise the risk to life safety. Although the original design of Manchester Town Hall incorporates open spiral stairs between all floors, the primary construction is blockwork, which allows fire compartmentation around rooms or collections of rooms to be quite easily achieved.


Manchester Town Hall closed to the public in early 2018 and will remain closed for refurbishment until 2024. In developing the fire safety strategy for this historic public building, there is still a long way to go and many challenges to overcome. There are of course the challenges associated with maintaining and protecting a heritage structure, but also the challenges of enabling safe public access to an important building, and to enable future generations to explore and appreciate this valuable Manchester asset


Paul Williams is associate director of fire engineering at Arup. For more information, view page 5


www.frmjournal.com JULY/AUGUST 2018 25


FOCUS


Doors are the weak point in this strategy. The


existing heritage doors are a varied collection of timber doors consisting of panelling and often also elements of glazing. Above many of the doors a ventilation panel can be found that is part of the existing ventilation to each room, ensuring a flow of air between rooms and the central corridors. As part of the refurbishment, a condition survey will be carried out to determine whether retained doors will achieve an adequate fire resistance. Adequate in this context is unlikely to be analogous to the fire resistance rating that modern standards expect. An assessment of the performance of the doors will therefore need to be undertaken, and doors upgraded as much as is reasonably practicable, without impacting on their heritage significance. At this stage, these upgrades are likely to include minor interventions such as installation of smoke seals at frames, and self closers to doors and over door panels.


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