Chapter 1 Smoke control overview
Design considerations for smoke control
Two occurrences will hinder smoke control:
•Plugholing
•Smoke feedback
Smoke control systems should be designed to address the problems that are caused by plugholing and smoke feedback.
Plugholing
Plugholing occurs when an exhaust fan pulls fresh air into the smoke exhaust (Figure 10). Plugholing decreases the smoke exhaust and increases the smoke layer depth. It has the potential of exposing occupants to smoke.
The maximum flow of smoke (Qmax) exhausted without plugholing depends on the depth of the smoke layer and the temperature of the smoke. If the required total smoke exhaust is greater than Qmax, additional exhaust vents will eliminate plugholing. The distance between vents must be great enough that the air and smoke flow near one vent does not affect the air and smoke flow near another vent.
Figure 10: Sample plugholing
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