The Fundementals of Smoke Control
Andover Controls Corporation 1-3
TOC
Using Pressure to Control Smoke
The basic concept behind controlling smoke, regardless of whether it is
with a dedicated or nondedicated system, is to use air pressure to confine
and (if possible) vent smoke from the building.
You cannot confine smoke by simply closing all access ways (such as
doors and vents) to the room that has the fire in it. Even with these
passages closed off, smoke can disperse throughout a building via
cracks, holes made for pipes and electrical wires, and spaces around
doors and windows. Smoke is driven through these small openings by
the expanding gases from the fire. Smoke can also be driven onto other
floors by the stack effect, which causes air to rise in buildings. The stack
effect is caused by the difference in the interior and exterior temperature
of the building. The following diagram shows how smoke can disperse
throughout a building.
Figure 1-1. Smoke Infiltrating Areas Adjacent to the Fire
Since smoke is carried by the movement of air, you can stop the spread
of smoke throughout the building by lowering the air pressure in the area
containing the fire and by raising the air pressure in the surrounding
areas and floors. The difference in pressure (also called the pressure
differential) between the smoke-filled area and the surrounding areas
acts as a barrier to the smoke, pushing it back into the smoke-filled area.
The next illustration shows how this works.
Area on Fire
Adjacent Area
Adjacent Area
Adjacent
Area
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