Even by the exacting standards of the health sector, the newly completed James Cook University Hospital on Teesside has a highly sophisticated fire strategy.
The site’s fully integrated, analogue addressable fire detection and alarm system was designed, supplied and commissioned by Novar, under a contract from Carillion Crown House. It consists of 26 Gent Vigilon control panels and thousands of loop-driven, combined sensor/sounders. Approximately 18,000 pieces of equipment have gone into the finished system.
The product of a GB pound 160 million PFI-funded project, James Cook University Hospital is an 1100-bed facility comprising 130,000m2 of new and refurbished estate.
The hospital’s requirement for fire compartmentation, coupled with its extensive use of mechanical ventilation, have inevitably led to a fire detection and alarm system of some complexity. In common with all NHS hospitals, the fire strategy calls for progressive horizontal evacuation of the building. As recommended in Health Technical Memorandum 82, it was also required that the output from alarm sounders is relatively subdued, an audibility level of 45-55dBA being specified in patient areas (adequate to alert staff without causing distress to patients). This has been achieved through the use of Gent sensor/sounders in ward corridors and staff/utility areas, where a higher sound level (65dBA plus) is acceptable. One of the advantages of these devices is that they are able to produce one tone to signal an evacuation and another very different one for an alert, thus avoiding possible confusion. Given that the fire plan involves phased evacuation, this is an important feature.
Of the 5200 detectors that have been installed, 3700 are combined sensor/sounders. These incorporate both heat and optical (smoke) sensing elements.
In the event of a fire, the Vigilon system will sound the evacuation tone in the affected zone and the alert signal in all adjacent areas, including on the floors immediately above and below. It will also implement a smoke containment strategy entailing the closure of doors that are normally held open and – in the new build part of the hospital – the closing of fire dampers in supply and extract ducts.
Normally, the main air-handling units (AHUs) would continue to operate to serve non-affected areas. However, if smoke dampers downstream from an AHU were to close, restricting air movement, then the fire system would automatically shut the plant down to prevent pressurisation of the ductwork. Additionally, the system monitors all 700 fire dampers at all times, to check they are correctly positioned.
Some 30 five-position key switches have been incorporated to allow firefighters to override the air supply and/or extract controls in any area. Provision of this override facility, which can involve inter-panel communications, added significantly to system engineering complexity.
Though detection in most areas is provided by the multisensor/sounders, there are also heat-only sensors, optical beam detectors and a number of aspirated smoke detection systems. A graphics-based Gent supervisor terminal has been installed in the hospital’s engineering department to enable central management of the system. In the continuously manned control room there is a Gent mimic panel, to provide site-wide indication of the location of any area/zone fire condition.
Chief Fire and Rescue Adviser’s guidance
