HEPA filter on domestic vacuum cleaner

My vacuum cleaner does not have a HEPA filter and I would like to get a cleaner that does.
Can someone who understands the physics of HEPA filtration help me understand HEPA a bit better please. Google is not much of a friend for this info!
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Is HEPA a registered trademark?
What technology does a HEPA filter make use of? Is it nothing much more impressive than a very fine aperture standard filter?
is the HEPA filter on a vacuum cleaner likely to need replacing more often than non-HEPA on account of the greater dust it traps?
Can a HEPA filter be washed or otherwise cleaned so that it can be reused? Or is the life of a HEPA filter so long that this is not a consideration.
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Thank you for any info.
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Will wrote:

I'm curious - if you don't actually know what HEPA is, why do you believe you need/want it?
<http://en.wikipedia.org/wiki/HEPA> <http://www.eh.doe.gov/hepa/index.html>
--
Grunff

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Then you haven't smelt the dust which blows up when I hoover using my current vaccuum cleaner!
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Will wrote:

From Google: http://www.eh.doe.gov/hepa/
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I got that far with Google but the site is full of heavy duty topics all of which seem to assume the reader knows the basics of HEPA. I couldn't find an intro or FAQ or primer there so then I posted to the newsgroup.
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Dear Will:

You like the benefit of efficient particle removal of a certain size (or larger), and you are willing to pay more for the bags, buy more of them, and change them more frequently.

No, but it is a recognized standard acronym.

Correct. Yet there are small modifications that can be made to the element to extend service life... by a few minutes.

Not "greater dust". It has a small pore size, and using it means blocking the small pores will block all flow.

Possible, but not likely. Water carries contaminants, and these contaminants scale out and block small pores.

Anything one could do to extend bag life, or reduce the number of bags used per annum would be a sales feature. But then, once you buy the vacuum cleaner, they have hooked you for replacement bags. Just like ink jet printers...

You have good links by the others.
David A. Smith
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Will wrote:

It may have become one, although it started life simply as an acronym.

It ii a fiberous mat - when talking about stanad alone filters ifusually with a large surface area enclosed in a container of some sort

The HEPA filter is usually the last filter in a sequence and hce is fed mostly clean air. It will trap the smallest and most penetrating particles including the carbon dust generated by the motor itself.

Not IME.

They last a reasonable time if you avoid things like sucking up plaster dust (or any other super fine clogging material)
--
Cheers,

John.

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Can I buy generic HEPA filtration material in the form of a sheet?
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Will wrote:

Why?
HEPA stands for High Efficency Particulate Air. It's simply a finer mesh so it traps smaller particles, typically 99.95% efficient in removing particles down to 0.3 micron. A human hair by comparison has a diameter of 60 -90 micron.

Not as far as I know, more an internationally agreed performance standard. Vacs for asbestos work to similar standards.

Yes sort of. HEPA's are more commonly found as final exhaust filters, the main filters trap the majority of the dust, leaving the HEPA to filter only the finer particles.

You can't wash then, but they last a reasonable time (see above).
Considerable benefits if you suffer from asthma, but they also reduce airbourne dust to almost zero, so you don't have to dust so often.
--
Dave
The Medway Handyman
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Never say never (or can't)!
The Dyson range includes some which have a 'Lifetime HEPA' filter in the exhaust air stream. The filter is intended to be hand-washed. It seems to be composed of a foam, which for what it's worth it's blue and 'squidgy'. Dyson recommends that the filter is washed 'at least every six months' and it should be air-dried (they recommend placing it under a radiator). Spare filter assemblies ( a yellow plastic cage containing the blue foam filter) are purchasable - (most folk keep one spare and one in use). I exchange the filter about every six months (honest ) ... the filter is quite black when I get araound to exchanging it and requires vigorous squeezing to restore it to its natural blue colour.

--
Brian
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Replying to myself ...
I asked here about HEPA and from the replies it seems that maybe I could get some HEPA standard filter material and cut it to shape to fit the final exhaust grille on my existing hoover. If air flow is badly impeded by this then I could remove the original filter material.
Q1) Assuming here are no other significant outlet vents on the hoover then would this work in reducing airborne dust?
Q2) Does air passing through a HEPA filter get slowed down more than it would when passing through a conventional filter? (Assuming all other things like area covered is the same.)
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Dear Will:
...

It will be.

Then the "muck" you vaccum up will build up on the fins of the "fan", changing its dynamic charateristics, and ultimately causing it to fail. This is a bad thing. Instead, increase the surface area of the external "bag".

Yes.
Likely the answer to your question is "no". Because you are trying to push that same volume of gas+ through a smaller total orifice, so the average speed must go up.
Also, some blower motors are cooled by the exit air stream. So be *sure* you do not constrict this airflow for long...
David A. Smith
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