Positive pressure

spicetek · Post by **spicetek** » Fri Jul 22, 2005 3:23 am

What % difference in total intake / output flow is ideal for keeping dust out of a case? Has anyone worked this out in terms of actual CFM ratings and case volumes?

I'm wondering if you can have substantially greater input pressure, or whether this just ends up moving hot air round the inside of the case.

Bluefront · Post by **Bluefront** » Fri Jul 22, 2005 4:18 am

Case pressure doesn't make a scrap of difference where dust is concerned, unless all the intakes are filtered. Once you have all the intakes protected with filtration, a neutral pressure setup is best for the dust problem. With such a pressure setup, there is much less tendency for dust to come through the cracks, while keeping the noise level down.

A pure positive pressure case (with filtered air being blown in) is probably the cleanest setup....but tends to be noiser than a neutral setup.

spicetek · Post by **spicetek** » Fri Jul 22, 2005 4:43 am

Bluefront wrote:Case pressure doesn't make a scrap of difference where dust is concerned, unless all the intakes are filtered. Once you have all the intakes protected with filtration, a neutral pressure setup is best for the dust problem. With such a pressure setup, there is much less tendency for dust to come through the cracks, while keeping the noise level down.

A pure positive pressure case (with filtered air being blown in) is probably the cleanest setup....but tends to be noiser than a neutral setup.

I'm being a bit cheeky in that this isn't actually for a silent PC, it's for a dust free setup (the room and intakes are already filtered), I just figured the good folks here know their stuff so I'd ask

So a pure positive setup would still cool effectively? That would actually be a lot easier.

I assume most people don't use filters in PC's due to the extra impedance / noise, in which case would a slight positive bias give a good noise / dust trade off?

IsaacKuo · Post by **IsaacKuo** » Fri Jul 22, 2005 5:51 am

spicetek wrote:I assume most people don't use filters in PC's due to the extra impedance / noise

Most people don't use filters because filters weren't included in their (stock) PC to begin with. Besides adding to the manufacturing cost, filters are a bad idea for Joe Average. Joe Average can't be bothered to change filters, and without doing that a filtered computer will choke to death on dust sooner than a non-filtered computer.

Personally, I don't use filters because I can't be bothered with the extra maintenance either. I haven't found dust buildup to be a problem so far, so I haven't had any reason to change.

Bluefront · Post by **Bluefront** » Fri Jul 22, 2005 6:28 am

spicetek.....I'm not 100% certain what you're asking. But yes, a filtered positive pressure case like you suggest, would remain the cleanest....assuming proper filter maintence. Then there is the problem of determining if you really have a slightly positive pressure case at all times...