PC case airflow directly affects component temperatures, and understanding positive versus negative pressure explains why identical fans arranged differently can produce genuinely different real-world thermal and dust results.
Positive vs Negative Pressure
Positive pressure: MORE air being actively pushed IN than pulled out
-> air is forced OUT through small gaps and
unfiltered openings, rather than being
actively drawn IN through them
-> genuinely LESS dust accumulation over time
Negative pressure: MORE air being pulled OUT than pushed in
-> air gets actively drawn IN through every
available small gap and unfiltered opening
-> genuinely MORE dust accumulation over time,
since unfiltered gaps become active intake points
Why Positive Pressure Is Generally Preferred
A case configured for slight positive pressure (marginally more intake fans/CFM than exhaust) means the small amount of air genuinely escaping through unfiltered gaps and openings is being pushed out, rather than dust-laden room air being actively pulled in through those same unfiltered openings — a meaningfully real, practical difference in how quickly dust accumulates inside the case over months of actual operation.
Practical Setup
Front and bottom intake fans (ideally behind dust filters), with rear and top exhaust — a standard, well-established layout that takes advantage of natural warm air rising while maintaining genuinely favorable intake filtering. Slightly favoring intake fan count (or fan speed) over exhaust achieves the positive pressure that keeps dust accumulation meaningfully lower over the system’s real operational lifetime.