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Dust extractor confusion


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Established Member
4 Aug 2011
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I currently require a new shop vacuum/ power tool extractor as my old one has finally become too annoyingly rubbish.
So I started having a look on the obvious websites ( axminster. D and M tools, ebay etc. ) for a suitable unit.

This seems to be a confusing market indeed. I have noticed that the Bosch gas 25/ gas 50 appear to be the same as the mafell s25/ s50 and also the metabo asr2025 seems to be the same as the gas 25/ s 25. However I noticed that the mafell version comes in a certified catagory M version where the Bosch cat M version is mentioned but not for sale. I mention these mainly because I like the self cleaning filters and used to use a bosch gas 25 when working for someone else.

Of course I would like the best filtration and thus safety possible so cat M looks like an obvious choice, but then what about HEPA I recently read an article in Fine woodworking where they tested various shop vac`s the winner was clearly a bosch gas 50 but with an american name. This version came equipped with Hepa filters. But I cannot find anywhere that sells Hepa filters for the gas 50 in Europe.

I have seen the very popular Festool extractors too but most appear to only be rated to cal L unless you go to the £900 plus models or the pro tool range.

The Makita 447 is cat M compliant but a bit pricey.
Also one must consider the running costs of these units, are they only certified cat M if using the specified bags, at £5 for a bag that may only last 1 or 2 days the ongoing cost is prohibitive.

I don`t mind spending decent money on decent kit at all. I believe it wise to buy good quality tools that last a long time but I don`t want to be ripped off on constantly buying expensive bags. Perhaps I could get a small cyclonic separator as well.

Ok Confused rant over.
Any advice or recommendations will be much appreciated. Ideally I would like to find a huge group test on all available extractors and shop vacs but I can`t find any at the moment.



Established Member
2 Oct 2009
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West London
OK, I'm no expert and this is all 'as I understand it' based on my own digging into the issue when I started to take dust extraction seriously.

For an extractor to comply with Category M standards, they need to have an airflow sensor that sounds/displays an alarm if the airflow drops below a set level e.g. if there's a blockage or if the bag is full. An extractor may be fitted with equivalent Cat M filters, or with filters that exceed that level of filtration (HEPA) but without the airflow sensor they can't be classed as Cat M vacs.

For example, AFAIK all current Festool Vacs (CTL and CTM) have the same level of filtration, but only the vacs with the airflow sensor can be classed as Cat M, even though in all other respects the L and M vacs are identical - details are all on festool.co.uk, btw. Also, notice in the technical description of the Metabo you mention, they refer to "Two filter cassettes, suitable for dust class M, transmittance < 0.1 %" - but don't refer to the actual vac as being Cat M compliant - probably because of the lack of airflow sensor.

Bear in mind as well - and again, this is 'as I understand it' - with the HEPA standard, it's the filters that are rated as compliant, not the vac that they're fitted to i.e. fitting an HEPA filter won't magically make an HEPA vac.

Re. filter bags, yes, they are expensive, but they are an integral part of the filtration process; FWIW I have a 20-odd litre vac in the workshop and fill a bag every week or two, which I consider to be a small price to pay for clean air, personally.

HTH Pete


Established Member
24 Jan 2012
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Axminster do the Numatic NVD750 which is pretty pricey on its own and even more expensive if you buy the separate HEPA module, but I must say I'm pretty close to ordering one myself. If that's too small there's the larger NVD1500 model!

I've been corresponding with Simon there, as I was a bit confused by the description on the website.

Hopefully some of the info below will be useful (compiled from a long trail of emails because I was being thick and edited slightly for clarity):

The hose size has no relation to the filtration level, the HEPA flow bag can be used with either hose but is only a filter and not a collection bag with the larger hose.

The central opening (51mm/32mm hose) has to be used if you want to use the HEPA bag as the collection bag. With the side opening (100mm hose) you still use the filter but the waste collects in the drum.

With the HEPA flow bag and 2 head filters the vacuum captures 98.7% @ 0.5µm and 96% @ 0.3µm.
With the addition of the HEPA module the filtration is 100% @ 0.5µm and 99.95% @ 0.3µm.

We still recommend using the HEPA flow bag with the HEPA module, if it isn't the filtration levels will be slightly reduced from the levels listed below and the life span of the other filters will also be reduced.


Established Member
12 May 2007
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Theres no such thing as a HEPA vacuum in Europe.It's misused like 0.5 micron, hospital standard and other sales chuff.Take claims like these with ahealthy skeptisism
Europe standardized on a simple system based on a mixture of British and German standards simplified into L,M and H class. It c

ii was going toi write reams onthi but my I-mac died and this computer is dung