Smoke-extract system takes up less space
The Colt Shaft active-fan smoke-extraction system for residential buildings, hospitals, schools, colleges, offices and hotels frees building designers from the constraints imposed by the need for fire-fighting cores in these types of building. It also extracts smoke more quickly than passive natural-ventilation systems. These cores are required in buildings over 18 m to an occupied top-floor. They are voids containing stairs, lifts and lobbies to provide fire fighters access to any floor and must be kept free of smoke. One approach to keeping these cores free of smoke if they are remote from outside walls is a BRE shaft of 3 m2. A Colt Shaft, in comparison, requires 0.6 m2 — 80% less space.Colt Shaft also solves two common problems associated with mechanical ventilation. First, even a small amount of extract from a fire-rated lobby could make doors difficult to open. Secondly, that negative pressure could cause smoke to be drawn from the fire-affected area into the lobby. Negative pressure is overcome by Colt Shaft by reducing the ventilation rate when the lobby doors are closed, using the signal from a pressure sensor to vary the fan speed. With all doors open, the fan runs at full speed. Comprehensive smoke tests witnessed by the London Fire Brigade have given Colt the confidence to believe that the Colt Shaft can achieve the same performance as a standard 3 m2 BRE Shaft.
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