Video Smoke Detection ProtectsLondon’s Newest Building

From any point of view the renowned “Gerkin”, originally thenew headquarters for Swiss Re's UK operations at 30 St MaryAxe in the City of London is a remarkable building.

Rising to 180m the 40-storey building, thrusting skywards,strikes a dramatic pose in the heart of the City and reflects thevibrancy of one of the world’s great commercial centres. Revolutionary in shape and function, the “Gerkin” incorporatesmany advanced methods of planning, design and construction.One unique design feature is the six light wells on every floorspiralling at 5-degree angles from the floor above down thebuilding. Created by offset, triangular cut out areas at the outerperimeter of the floors, the light wells are intersected bytransverse, major structural floor plates in series of between twoand six storeys throughout the height of the building.

The deepest (‘six pack') light well voids extend to approximately25 metres in depth. As the light wells provide ventilationthroughout the structure it was imperative that an early form ofsmoke detection was applied to these areas because smokewould most certainly travel through these areas in the event ofa fire. Hilson Moran Partnership (HMP), the Building ServicesConsulting Engineer, was charged with the responsibility to findthe most efficient fire detection system to protect these areas.

The use of systems involving conventional smoke detectors suchas beam detectors or aspirated smoke detection systems wereall considered and discounted for different reasons. Also, theArchitect wanted to keep the areas as ‘clutter free’ as possibleso as to retain the aesthetic features of the light wells.

An engineer at Hilson Moran, who had seen the new concept ofCCTV Video Smoke Detection (VSD) explained on BBC’s'Tomorrow’s World' proposed further investigation. Theirenquiries led HMP to D-Tec, the inventors and developers of theCCTV VSD technology. Demonstrations of the technology werearranged so that the Client, Swiss Re, the architects, the DistrictSurveyor and the main contractor could evaluate the system andmake a decision as to whether it would give the desired level ofprotection. The demonstration was carried out in the new SwissRe Tower where a 30 second burn smoke pellet was ignited onthe fourth floor and a camera set up on the ninth floor. Uponignition the system picked up the smoke within thirty seconds.Several tests were made and all gave similar detection rates.One of the key issues was identified during testing; the smokedid not follow the same flow patterns as the testing progressed.As the VSD System does not rely on smoke reaching a specificpoint it can detect the smoke no matter what the airflowdirection. This made the decision making process somewhateasier as it soon became apparent that no other system couldoffer this level of protection.

The instruction to install a six-camera system to protect thelight wells was issued. It was also agreed that the sametechnology would be utilised in the main lobby where theexisting security cameras would be used also for fire protection.The lobby height was 6.5 m and again the architects specifiedthe minimum of services’ clutter. By running D-Tec software on6 of the security cameras, smoke detection was achieved withthe minimum of disruption.

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Video Smoke Detection

The installation was carried out in phases so as to fit in with themain construction schedule. In essence the system wasintegrated with the security CCTV System, the main Fire Paneland the Building Management System. All components of thesystem were completed on schedule and a date was set for thedemonstration to the District Surveyor and Swiss Rerepresentatives.

The lobby area was tested first. A portable smoke generator wasbrought in so that no residual material would linger in the brandnew lobby. The system detected the smoke within thirty secondsand the sounders and voice annunciation system were initiated.Then the light wells were tested where there was far moreintegration with other systems in place. Again, a portable smokegenerator was used and again the system detected the smokewithin 30 seconds. The detection initiates a number of buildingfunctions to operate. Firstly the Fire alarm sounders begin andthe voice annunciation system advises people within the 4th to9th floors to evacuate. Also the automatic diamond-shapedwindows on the floors 4 - 7 close and the windows on floors 8and 9 open. At the same time smoke curtains drop down aroundeach triangular light well 2 meters on floors 4 to 7 and on levels8 & 9 the curtains drop down to the floor. This provides a spiralchimney effect to vent the smoke out of the building.

The District Surveyor was very impressed with the technologyand believes that many other buildings will benefit from using theVSD Technology, especially when large atriums are becomingmore popular with designers. The fact that the same CCTVsecurity cameras can be used as fire detectors means that thesystem becomes a cost effective viable solution.

It is likely that the D-Tec system will be utilised for the light wellsbetween the major floor plates on other floors, as they arecompleted and let in the building.

www.dtec-fire.com

Video Smoke Detection

Head OfficeDetector Technologies, Unit 4, Delta Park, Wilsom Road, Alton, Hampshire, GU34 2RQ, UK Tel: +44 (0)870 4581517 Fax +44 (0)870 4581518 info@dtec-fire.com

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