Actionair Smoke/Shield Dampers form part of the fire safety systems
protecting the new Darvent 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, Darvent 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.
On the "Street"
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 Smoke/Shield 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 Smoke/Shield Damper; opening units where
required to vent fumes and smoke safely to 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.
