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Applications of smoke control methods
BAS-APG001-EN 11
Natural smoke venting technique
The natural smoke venting technique employs vents in the atrium ceiling
or high on the atrium walls to let smoke flow out without the aid of fans
(
Figure 8). The applicability of natural venting depends primarily on the
size of the atrium, the outside temperature, and the wind conditions.
When smoke is detected, all vents open simultaneously. The flow rate
through a natural vent depends on the size of the vent, the depth of the
smoke layer, and the temperature of the smoke.
Figure 8: Sample natural smoke venting technique
Smoke filling technique
The smoke filling technique allows smoke to collect at the ceiling. Without
fans to exhaust the smoke, the smoke layer grows thicker and descends.
Atrium smoke filling is viable when an atrium is of such size that the
time needed for the descending smoke to reach the occupants is greater
than the time needed for evacuation.
People movement calculations determine evacuation time. For
information on people-movement calculations, refer to SFPE 1995, Fire
Protection Engineering Handbook.
Note:
Thermally activated vents are not appropriate for natural
venting because of the time delay for opening.