Page 11 - Caswell Firesafe Manual 2018

Pressurisation System

The principal function of a Pressurisation system is to create a higher air pressure in the protected area in
order to prevent the ingress of smoke from surrounding rooms.

Typically these systems are used in the following situations:

• Protected escape corridors
• Stairwells
• Lobbies
• Fire-fighting shafts (i.e. serving deep basements)

The diagram below illustrates a typical Pressurisation system.

BRITISH STANDARD VERSION
TYPICAL PRESSURISATION DUCTWORK SYSTEM
DIAGRAM BASED ON THE PRINCIPLE OF EN12101-6 (FIGURE 8B)
PRIMARY & BACKUP FANS

PENETRATION SEALS
OTHER PLANT ROOM TO BS 476 PT24
OVER PRESSURE
RELIEF DAMPER

SMOKE CONTROL DAMPERS
PROTECTING INCOMING AIR
FROM EXTERNAL FIRE
EXPOSURE - WITH ALTERNATIVE
PRESSURISED INLET POSITIONS
LOBBY
NORMAL FLOOR AREA AIR
RELEASE
VENTS
SERVICE RISER
CONTAINING
OTHER SERVICES
PRESSURISED PRESSURISED
STAIRWAY LOBBY
NORMAL FLOOR AREA
FIRE RESISTING
PRESSURISATION DUCT
PRESSURISED
LOBBY
NORMAL FLOOR AREA

PRESSURISED
LOBBY
NORMAL FLOOR AREA
FIRE RESISTING WALLS (for compartmentation) FIRE RESISTING SMOKE OUTLET DUCTWORK, RETAINING
FIRE RESISTING FLOORS (for compartmentation) CROSS SECTIONAL AREA OF MORE THAN 75 OF DUCT.
STABILITY, INTEGRITY & INSULATION RATING EQUAL TO
COMPARTMENT WALLS, UNLESS SHAFT IS DEDICATED,
THEN STABILITY & INTEGRITY ONLY IS REQUIRED
ELEVATION DUCTWORK SUITABLE FOR CLEARING SMOKE.
OFTEN 1 HOUR INTEGRITY TO BS 476 PT 24 - ISO 6944
RETAINING A CROSS SECTIONAL AREA OF MORE THAN 75.
These systems are used to introduce high-pressure, fresh 'make up' air to keep the protected area free from
smoke and allow the building's occupants sufficient time to escape. As the system needs to operate at
elevated temperatures, fire dampers cannot be used and therefore fire resisting ductwork needs to installed.
BS 9999 gives guidance on the use of Pressurisation systems for the purpose of smoke control within
buildings.

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