Case fan and ventillation logic question

[Plo_Koon]

I was wondering about the positive and negative pressure logic. Can someone explain why positive pressure yields less dust inside the case even though there are more fans blowing air into it, whereas negative pressure setups just blow air outward meaning they should theoretically expel dust from the inside instead of sucking them in

 

[Motopsychojdn]

Because pressure staus is irrelevant to the fans actual intake/output,
you have a ton of fans pushing air into a case, it will try to expel the excess air through any cracks or gaps it can, keeping dust out.

if you have a load of fans pushing air out of the case, it creates a vacuum effect and sucks in through those gaps, and thats when dust builds up,
I run three intakes to one exhaust and haven't 'needed' to dust my Pc since I built it back in october (I only clean my rig due to Ocd )
My Rig's a bit modded anyway and probably not a good comparison for most peoples cases
**Edit, after answering your thread, i saw this a couple of lines down, some nice links in there that may help you
http://www.tomshardware.co.uk/forum/329241-10-positive-negative-pressure

Moto

 

[Plo_Koon]

Now I get it!

But what if there are no other exit points/vents apart from the fan grills themselves (say 4 of them - 2 in the side and front and back)? Won't the dust just get circulated if they are a bit far from the exhaust fan?

Also, since I'm assuming your one exhaust fan is the one behind, won't the side intake fan cause a conflict with the cpu fan (one blowing in and the other blowing out)?

 

[Motopsychojdn]

If we're talking specifically about my build, the 'sidefan' is actually on the rear of the case, blowing onto the back of the motherboard/Cpu,
I have a mod where I have a fan over the Cpu waterblock that blows onto the block
And where you say side intake causing conflift, the Cpu fan on a normal heatsink also blows towards the heatsink, not away from it, so even if you have a sidefan that side, they would both be blowing the same way
Moto

 

[Plo_Koon]

Best answer selected by plo_koon.

 

[Motopsychojdn]

Glad to help man,
Moto