Darent Valley Hospital, Kent

Actionair SmokeShield PTC 'ES' Rated Automatic Fire Dampers form part of the fire safety systems protecting the Darent Valley Hospital at Dartford in Kent. Built by a team headed by Carillion, the hospital is the first to be constructed under the Private Finance Initiative (PFI) scheme.

Consulting engineers Zisman Bowyer Partnership undertook the detailed design for the hospital building services. Designed as an Acute General Hospital, Darent Valley is a 400-bed unit with six principal operating theatres, a further three day theatres and a self-contained maternity suite.

The majority of these special units are located in the two-storey East Wing, which also has some patient accommodation. The ward areas, are chiefly located in the three-storey West Wing and are mainly naturally ventilated.

Mechanical ventilation and air conditioning load is required to meet the needs of specialist areas such as operating theatres and pathology labs, the toilets and bathrooms located throughout the hospital. While the operating theatres obviously require full air-conditioning including humidity control, the deep plan design of the hospital also requires tempered supply air conditions. Principal building services equipment including the air handling units is located in rooftop plantrooms.

The layout of the hospital follows the "street" principle, with nucleus style wards radiating at right angles from the central thoroughfare on each storey. Ventilation and air-conditioning services follow the line of the street with main supply and both "clean" and "dirty" extract ductwork located in the ceiling void with subsidiary sections radiating out into the nucleus units as required.

To ensure easy access for servicing, well over 95% of the Actionair SmokeShield Dampers installed in the hospital are located at the plantroom end of the ductwork runs. They form an integral part of a sophisticated fire strategy, which has been purpose designed to protect the building. Should a fire situation be detected in any individual zone, the system will automatically alert any designated adjacent zone and fire suppression, smoke control and emergency evacuation procedures are initiated in that overall area, while ventilation and air conditioning services to the rest of the hospital continue as normal.

Although the status of the Actionair Dampers is routinely monitored by the BMS system, actual control of the units is via the self-contained fire safety system. The Dampers are set to close in the event of a fire situation; however, the "fireman's override" switches on the main control panel in the West Wing giving brigade officers the facility to control each individual SmokeShield Damper, opening units where required to vent fumes and smoke safely to the atmosphere. Controlling smoke in this way can aid evacuation of the affected area and speed access by fire officers in order to tackle the source of the problem.

Cover photo by Claire Stretch CC