Page 9 - Caswell Firesafe Manual 2018

Smoke Extraction / Car Park Extract Systems
Smoke extraction involves the evacuation of products of combustion, such as smoke and toxic VOC gases,
which could reduce visibility and impair human functions. This may impede the efforts of emergency
services in finding the seat of the fire and so increase the time it takes to extinguish it.

As previously stated, installing thermally activated fire dampers in these systems would prevent the system
from fulfilling its function; therefore the system, from the point it first passes through a compartment wall,
must be fire resisting.

The diagram below illustrates a typical Smoke Extraction system.

BRITISH STANDARD VERSION
TYPICAL CAR PARK EXTRACT SYSTEM
AS APPROVED DOCUMENT 'B' OF BUILDING REGULATIONS
FANS DESIGNED TO OPERATE AT 400°C FOR 1 HOUR, EACH FAN DESIGNED
TO RUN AT 50 OF THE NORMAL AND SMOKE VOLUMES, AND DESIGNED
SO THAT EACH FAN CAN OPERATE SINGULARLY AND SIMULTANEOUSLY.
NON-RETURN DAMPERS
SUITABLY FIRE COMPARTMENT
PROTECTED FAN WALLS
NO FIRE DAMPERS SHOULD
BE USED IN ANY
CAR PARK EXTRACT

PENETRATION SEALS
TO BS 476 PT24
FIRE COMPARTMENT FLOOR

TYPICAL BASEMENT CAR PARK EXTRACT, GROUND LEVEL
6 AIR CHANGES PER HOUR NORMAL OPERATION
10 AIR CHANGES PER HOUR SMOKE EXTRACT.

LOW LEVEL
AIR INLET

FIRE RESISTING WALLS FIRE RESISTING, STABILITY & INSULATION DUCTWORK
FIRE RESISTING FLOORS
NON-FIRE RESISTING WALLS DUCTWORK CONSTRUCTED OF METAL WHICH HAS A MELTING POINT NOT
LESS THAN 800C (INCLUDING ALL ELEMENTS, RIVETS, SUPPORTS AND FIXING
BOLTS ETC. (E.G. STEEL DUCTWORK WITH ALL STEEL COMPONENTS).
ELEVATION
Even if the system is self-contained within its own compartment it must be capable of maintaining its ability
to operate and clear smoke at the elevated temperatures in the development phase of a fire.

Car parks requiring mechanical ventilation must have separate and totally independent extract systems due
to the polluted nature of the air. Fire dampers should not be installed in car park extract systems and as
such the systems should be fire resisting and treated as a dedicated smoke extract function; with the
requirement to maintain 75% of their original cross-sectional area under fire conditions.

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