computer has a side vent that takes air to the CPU and this vent has no
filter. This seems to now be universal. I could find a case with filters for
the front fan but not the side vent.
My front filter after 12 months is shown below and shows that dust is a problem.
Recently a friends computer (no filters at all) with a pentium 4 3000mhz started slowing
down and eventually stopped when doing intensive tasks.
You can just imagine how the fluff has packed the cooling fins below
Cleaning this part of the computer is not easy and I decided to do
something about preventing it on my own computer.
filter placed over the side vent will have to offer very little
resistance to air flow. Most fan filter frames you can buy are designed
to work with the direct air connection from a fan and the full suction
of the fan is available to drag air through the filter. This is not the
case with the side vent. The side vent is supposed to have its
internal extendable inner air guide positioned 12 to 20mm from the top of the fan
(see Intel Chassis Air Guide V1.1 Sept 2003).
Note that the correct positioning of this guide seems to
often be overlooked when the computer has been assembled by
smaller commercial system builders. In both of the computers
mentioned here it was not extended at all..
is the trace from SpeedFan showing parts of two identical runs of
Orthos stress test. The LHS is with the air guide fully retracted and
the RHS with the air guide positioned 16mm away from the top of the
fan. The test shows about a 2C improvement in the CPU temperature. The
inlet temperature at the time was 22C and the exit temperature at the
peak 26C. The case was to the Intel 1.1 air guide standard and was
fitted with 120mm front and rear fans. Less well ventilated cases may
benefit more from the correct positioning of the air guide. One simple
way of checking the air guide to fan clearance is to place the end of a rule on
the top of the fan and sight across the case edges. You can confirm
your measurements are correct with the simple tool below.
something like this, then to check that you have the air guide set
correctly pass it through the air holes in the case (from the inside) and with the case
side back on, push it onto the top of the fan and mark the stem where
it exits the case. If you have placed some graduations on the card you
can read off the clearance by sighting across the air guide with the
The filter described below may cause your computer to overheat and the
following description is only a report of what I did and not a
recommendation that you should follow. If YOU decide to try something
along these lines you should do your own temperature tests to determine
its suitability and take all the responsibility for any problems upon
Two things are needed to make a filter—some kind of filter material and
a frame of some sort.
have been on the lookout for some sort of filter material
and bought various things that caught my eye. Chux cleaning
was given a try but proved to restrictive. I recently noticed that my
daughters cloths drier had a fine nylon mesh filter (ours uses
foam). Googling revealed the suggestion the womens stockings could be
used. I tested a 15 denier stocking and found it had very little air
resistance and a .5mm triangular weave. The nylon mesh on my air
conditioner filter is 1mm square so it seems reasonable choice.
15 denier stocking weave with 1mm ruler marks in background.
a test a section of stocking was just taped across the vent. This is
far from optimal as the filter area being used is only as big as the actual holes in the vent
I saw a Short round CD/DVD container
and knew I was on
Cutting some way in from the edge gives the frame some strength.
This is fiddly and I had to resort to a rubber band.
Electrical tape went over the rubber band.
The base of the CD/DVD container was cut out with a fret saw and holes
drilled for the mounting screws.
was a flange on the underside of the base that was just where the holes
were to go and that was removed so the drill would not be pushed off
The ring could be more easily mounted with double sided tape or blue
The air guide showing how it can be extended.
special self tapping screws that had held the air guide were too short to mount to the filter base.
I have seen longer ones available but instead used bolts that passed
through the existing holes and will enable the original screws to the
reused if the case is returned to normal. Nuts tend to come loose and
can kill a computer so I painted on something to prevent that
Here is the finished result.It will look a lot better on a black case I am sure.
Taking the filter off to clean is a simple twist.
I can see fluff building up on it after a few days but its
performance will require more testing.
I can not detect any rise in temperature when it is fitted after
15minutes of 100% processor load.
the stocking filter is not your preference and you have access to
something better like special low restriction filter foam, it
could be made a press fit
into the recessed top of the CD/DVD container. With
foam you could cut out a pattern into the top of the
give support to the foam. Note, the filter needs to offer little
resistance because the air giude (snout) when correctly positioned
is not a tight fit to the CPU fan.
The graphics card air vents below remain uncovered until I can find a
graphics card has no fan so I can get to the heat sink to clean it
easily but at least now the hard to clean CPU heat sink is
getting mostly filtered air.By
the way. The amount of dust is proportional to the amount of air that
flows (and the environment). If your computer sits for long periods
with the fans running when it could be in sleep mode all you are doing
is wasting electricity and adding dust to the inside. Setting your
power saving options and even variable fan speed if it is available
could make a huge difference to the dust build up.
on my over clocked (2400MHZ) E2140 CPU @ 100% on both cores
less than 0.5C rise with the stocking filter as shown.
conditioning filter manufactures are a source of filter material. This
is a mesh filter that has approximately 1mm openings and attracts dust
by becoming electro statically charged. The material has a 3D profile so
keeping it away from the surface of the case to increase the area of
air flow is not quite so important. It is quite stiff but will
fray at the edges unless something is done to prevent it. Painting the
edges with nail polish should do the trick.
hook side of self adhesive velcro attachers well to the mesh and it
could be placed all around the vent. The mesh is then easily removed
you can get this material you could incorporate it in the "CD" mounting
above for the least possible restriction or dispense with the "CD"
method and just velcro a patch over the CPU vent hole.
To test how stocking compares with a commercial filter it is necessary
to ensure that the same amount of air flows through each.
took a section of the commercial filter and fixed a square of stocking
on each side so that air had to pass through in one area stocking then
filter and in another area filter then stocking. Simply put stocking
was on the front in one area and on the back in another. I set this at
the back of a pedestal fan and went dust hunting with a hand broom. the
dust was dislodged from the broom and carried through the filters.
Visually, the stocking collected just as much dust as the filter.
However a closer look at the commercial filter at 10 X revealed that the
electrostatic feature was working, see below. Very
little of the lint type dust passed the stocking and was
collected by the filter
underneath (see picture) which is confirmation that the stocking was
doing a reasonable job.
Because it has a flat
surface the stocking may become clogged sooner than a commercial filter material but
this is easily seen and cleaned in this application.
this picture of the rectangular side vent filter after a few days
of use, you can see that the commercial filter material traps and holds
very fine particles that would easily fit through the holes in the
weave. I would presume electrostatic attraction plays a part in this.
Stockings that were anti static treated would not attract fine
particles in this way and the fine threads used may not hold them.
of this material was placed under the stocking in the round holder
above for a long term test. This revealed that a stocking is not that
effective as it passed about 50% of mostly finer dust.