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Old December 28, 2012, 11:16 PM
Generic User #2 Generic User #2 is offline
Allstar
 
Join Date: Nov 2008
Posts: 560
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positive pressure = more fans blowing in than out
negative pressure = more fan blowing out than in

positive pressure is preferred nowadays because it keeps dust out. air is constantly being forced out of the case through the open fan mounts and tiny cracks( overpressure inside the case ) and keeps dust from sneaking in.
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