Purpose of Hepaflow Filter Bags for NDV750 extractor

[Tetsuaiga]

Can anyone tell me what these actually do?

I thought usually with filtration stages you have large progressing passing on to smaller sizes, I think the hepaflo filters very small particles so why when you use it on one of these extractors is it used as a first filter? =s.

I probably have some mistake in my knowledge here which is why I don't get it.

 

[Random Orbital Bob]

I thought hepaflo filters are designed to extract allergens from the air stream they're sucking. As such they're good for asthmatics, hay fever sufferers etc (I think). In other words the filters are incredibly fine.

 

[Shrubby]

Hepaflo is just a trendy (and misleading) brandname
If you look at the woodwork vacuums HML there is a finer bag called microflo
Matt

 

[Stuart]

HEPA filters are "high efficiency particle arrest" and are what are used in asbestos removal air lock filtration systems and laboratory air lock set ups. If they are used in a woodworking workshop the filters are so fine they would be clogged up within minuets.
A company might be using the word hepa as part of their marketing but I doubt they are true HEPA filters as they would not work in a woodworking environment for long. For more details google HEPA and you will find the particle size and filtration factors but from memory it is 99.8% down to 5 microns. The diameter of human hair varies between 17 and 100 microns so you see how fine it is. Hope this helps without being too technical

 

[Tetsuaiga]

I think woodworking dust filters can go down to .5 and .3 microns

 

[Random Orbital Bob]

they do indeed. I remember when I bought my first Record power DX the filter was rated to 5 microns because I seem to recall that was what was needed for mdf dust.

 

[shed9]

As I understand it, the Festool CT Vacs can be fitted with HEPA filters and are HEPA certified. The standard filter is 1 micron whereas the HEPA variant is 0.3 microns. Neither filter will clog with wood.
To sell HEPA filters, vendors are required to have them certified as HEPA complaint as required in certain legal situations however I would challenge the reality of this in some cases.
There is another category rating in the L and M class, the only difference being a little buzzer on the M class that goes off should the filter not be as effective as it should; for asbestos this is a must but for woodworking it's a bit of an overkill.

To be honest I would challenge most wood workers to tell the difference of HEPA and non-HEPA in real World use.

In response to the original query re: why use a fine filter as the first stage, in reality not all the filters are there for the benefit of the user's air quality, some are there to protect the motor - ironically most vacuum turbines will not operate properly unless the air passing through them is very clean.

 

[Shrubby]

You're mistaken
Hepa certified is meaningless in Europe
The test standards for filters are complex - En1822 should cover HEPA and ULPA grades which are tested to MPPS.
Manufacturers still quote BIA standards like BIA-C and BIA-G which are both used in woodworking
European standards L,M,H cover the entire machine not just filter media ( EN 60335-2-69 AA ) this includes the airflow monitor and emptying the machine without being exposed to dust etc etc
The situation isn't helped by manufacturers and retailers using smoke and mirrors to sell junk
end of rant
Matt

 

[MG1977]

Since u can buy a seperate HEPA filter for the Numatic vacs I'm assuming there must be a technical difference between these and the 'hepaflo' bags...or why would anyone purchase the filter at £120?

Michael