1-5
3. Turn OFF the air inlets and air returns of the areas that are neither being pressurized nor
depressurized (i.e., areas far away from the fire). Turning OFF the air return prevents the
smoke that is being vented into the return air system from coming into the smoke-free area.
In cases where there are large openings (such as an open doorway) between the area on fire
and an adjacent area, smoke can be confined by a large volume of air. Pumping large
amounts of air through the adjacent space creates a constant draft through the opening into the
smoke zone (as shown below).
CENTRIFUGAL FAN
Figure 1-3. Confining Smoke with a Large Volume of Air
The draft through the open space keeps back the smoke, confining it to the smoke zone. The
amount of air required to keep the smoke from penetrating the open space is quite large. Avoid
this type of situation when possible.
To contain smoke by using pressure, you must divide the building into “Smoke Control Zones.” A
floor or several floors of the building can be considered a single zone or a single floor can be
broken into a number of zones. A zone must be separated from other zones by smoke dampers,
airtight doors, and smoke-proof barriers.
When a fire occurs, the smoke control system can then pressurize all of the zones around the zone
where the fire initiated (called the “Fire Zone”), isolating the smoke to that single zone.
If the smoke control system is non-dedicated, the layout of the smoke control zones should take
into consideration the layout of the HVAC system. You should place multiple areas served by the
same HVAC controls in the same smoke control zone. Also, the smoke control zones must
conform to any fire control zones that have been established, because the smoke detectors are tied
into the fire detection system. Also, keeping the smoke control zones and the fire control zones the
same makes it easier to coordinate the two systems.
Controlling Smoke Movement, Continued
Basic Concept
Creating
Smoke Zones
IR
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AIR
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