Video Smoke Detection protectsLondon’s newest building

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

Rising to 180m the 40-storey building, thrusting skywards, strikesa dramatic pose in the heart of the City and reflects the vibrancy ofone of the world’s great commercial centres. Revolutionary inshape and function, the “Gherkin” incorporates many advancedmethods of planning, design and construction. One unique designfeature is the six light wells on every floor spiralling at 5-degreeangles from the floor above down the building. Created by offset,triangular cut out areas at the outer perimeter of the floors, thelight wells are intersected by transverse, major structural floorplates in series of between two and six storeys throughout theheight of the building.

The deepest (‘six pack') light well voids extend to approximately 25metres in depth. As the light wells provide ventilation throughoutthe structure it was imperative that an early form of smokedetection was applied to these areas because smoke would mostcertainly travel through these areas in the event of a fire. HilsonMoran Partnership (HMP), the Building Services ConsultingEngineer, was charged with the responsibility to find the mostefficient fire detection system to protect these areas.

The use of systems involving conventional smoke detectors such asbeam detectors or aspirated smoke detection systems were allconsidered and discounted for different reasons. Also, theArchitect wanted to keep the areas as ‘clutter free’ as possible soas 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 Swiss ReTower where a 30 second burn smoke pellet was ignited on thefourth floor and a camera set up on the ninth floor. Upon ignitionthe system picked up the smoke within thirty seconds. Several testswere made and all gave similar detection rates. One of the keyissues was identified during testing; the smoke did not follow thesame flow patterns as the testing progressed. As the VSD Systemdoes not rely on smoke reaching a specific point it can detect thesmoke no matter what the airflow direction. This made thedecision making process somewhat easier as it soon becameapparent that no other system could offer this level of protection.

The instruction to install a six-camera system to protect the lightwells was issued. It was also agreed that the same technologywould be utilised in the main lobby where the existing securitycameras would be used also for fire protection. The lobby heightwas 6.5 m and again the architects specified the minimum ofservices’ clutter. By running D-Tec software on 6 of the securitycameras, smoke detection was achieved with the minimum ofdisruption.

C A S E S T U D Y

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

Contact Details

US OfficeAD Holdings Inc. 3391 Town Point Drive, Suite 100 Kennesaw, GA 30144Tel: 770-874-8750 Fax: 770-874-8759 Email: stuart.fuller@dtec-fire.com

www.dtec-fire.com

The installation was carried out in phases so as to fit in with themain construction schedule. In essence the system was integratedwith the security CCTV System, the main Fire Panel and theBuilding Management System. All components of the system werecompleted on schedule and a date was set for the demonstrationto the District Surveyor and Swiss Re representatives.

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 and thevoice annunciation system advises people within the 4th to 9thfloors to evacuate. Also the automatic diamond-shaped windows onthe floors 4 - 7 close and the windows on floors 8 and 9 open. Atthe same time smoke curtains drop down around each triangularlight well 2 meters on floors 4 to 7 and on levels 8 & 9 the curtainsdrop down to the floor. This provides a spiral chimney effect to ventthe smoke out of the building.

The District Surveyor was very impressed with the technology andbelieves that many other buildings will benefit from using the VSDTechnology, especially when large atriums are becoming morepopular with designers. The fact that the same CCTV securitycameras can be used as fire detectors means that the systembecomes 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.

Video Smoke Detection