# What does the "micron rating" of a dust collector mean?



## clagwell (Dec 20, 2018)

What does it mean when a dust collector is advertised to have a "1 micron" filter? I don't know what a "1 micron" filter is. I can't find any industry or government standards or test methods that define a micron rating for air filters. Everything I've seen rates collection efficiency.

So, I'd really like to hear your opinion on the meaning of a "micron rating" for a dust collector filter. My opinion is that it's just marketing fluff that has no defined meaning.

What do you think?


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## DaveMills (Jan 17, 2020)

I've always assumed it meant that when in good working order (i.e. new) it filters out everything larger than one micron.


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## GR8HUNTER (Jun 13, 2016)

a metric unit of length equal to one millionth of a meter :<))))


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## Fresch (Feb 21, 2013)

https://www.envirosafetyproducts.com/resources/dust-masks-whats-the-difference.html
You can find wood dust size on this list, 
GR8HUNTER has the correct size.


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## clagwell (Dec 20, 2018)

> a metric unit of length equal to one millionth of a meter :<))))
> 
> - GR8HUNTER





> https://www.envirosafetyproducts.com/resources/dust-masks-whats-the-difference.html
> You can find wood dust size on this list,
> GR8HUNTER has the correct size.
> 
> - Fresch


Yes, good information there. My question though, was about the filter, not the dust. That is, what does a so-called "1 micron" rating tell you about the filter efficiency?


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## GR8HUNTER (Jun 13, 2016)

sorry I misunderstood :

filter efficiency refers to a measure of a filters ability to collect and retain particles of a specific size example if a filter can collect and retain 95% of particles that are 25 micron-sized or larger the filter can be said to be 95% efficient at 25 microns In other words a micron rating of 25 at 95% efficiency :<))

I hope this is clear to you its hard to explain


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## wapakfred (Jul 29, 2011)

When a filter says it's "1 micron", to me that's always meant the pore size in the filter. A 1 micron filter will actually capture smaller particles once a dust cake has built up on it. Some bags (like AFF) claim that the dust cake is part of the filtering media and their bags are meant to shed excess dust cake (the singe the fuzz off the inside to accomplish this). A lot of tests I've read have the bags/filters "seasoned" by sucking an amount of flour or fine sawdust through them before trying to measure filtering efficiency. But Tony described the way the filtration efficiency should be stated, it will remove xx% of particles xx micron in size. Not many do that.


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## ibewjon (Oct 2, 2010)

I looked at AAF bags, problem was I needed a second shop just for the bags. Good filtration needs a large area of filter to pass the air out. And yes, what I have read goes with the percentage of particles a particular micron size and larger. So not only is size important, percentage rating is also. A 10%rating on a 1 micron filter leaves 90% of the partials floating around the shop.


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## mdhills (Mar 12, 2011)

I believe this is a marketing description of the filter.

For example, the JET DC1100 canister filters are marketed as "2um".
If you read their brochure, they give a bit more information about the filtration:
-98% of 2um particles
-86% of 1um particles

It isn't clear if this is the filtration as measured with the machine or based on the specification of the filter media alone.

You can see another example with the filtration for Oneida's Dust Gorilla cyclones:
- HEPA-certified filter medai - 99.97% efficiency at 0.3um (MERV Rating 16+)
(I believe this is the rating of the filter material itself, but this is supposed )

Wynn NANO filter for clearvue cyclones:
- 99.999% at 0.5um (MERV Rating 15)

You might enjoy readng the FAQ at Wynn: https://wynnenv.com/faq/

Matt

Matt


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## clagwell (Dec 20, 2018)

> I believe this is a marketing description of the filter.
> 
> For example, the JET DC1100 canister filters are marketed as "2um".
> If you read their brochure, they give a bit more information about the filtration:
> ...


Oh good, thanks, I hadn't seen that. So if that's dust spot efficiency data then those are a MERV 12 or 13 filter before loading.



> It isn t clear if this is the filtration as measured with the machine or based on the specification of the filter media alone.


Yes, that's always a good question. There's also the issue of the collection efficiency at the tool, which is rarely above 90%, making filter numbers greater than that not all that useful.



> You can see another example with the filtration for Oneida s Dust Gorilla cyclones:
> - HEPA-certified filter medai - 99.97% efficiency at 0.3um (MERV Rating 16+)
> (I believe this is the rating of the filter material itself, but this is supposed )


I also think that it's only the filter media they are claiming to be HEPA. The MERV rating is probably the assembled filter. Not that they say MERV 16 +/- not 16 +, so that's likely just an estimate, not a tested value.



> Wynn NANO filter for clearvue cyclones:
> - 99.999% at 0.5um (MERV Rating 15)


I think the higher rating applies after a certain number of load/clean cycles and the MERV is the initial rating. See this: https://wynnenv.com/woodworking-filters/filter-efficiency/


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## therealSteveN (Oct 29, 2016)

Fred's answer is correct. It talks of the pore size, so theoretical just less than 1 micron will plausibly zip right through. Realistically though if said dust spec lands in between the "open" areas it won't zip, and may stay lodged indefinitely.

In reading filtration the "effectiveness" is going to be the % it will catch, so P or N 95 is LESS effective than P or N 100. So a 95 will stop 95 % of the substance sized to be caught on the filter, and a 100 will stop 99%, maybe +, depends on who's book you read and the fraction and numbers they present. Niosh doesn't sell anything except explanation handbooks, neither does OSHA create a product. Manufacturers of air filtration products do have a company "Org" they have seemingly created to do their testing, and based on that they have sprung new %, and lowered the particle size with approximately the same filtration %, to much lower particles, now suddenly we have HEPA, and particles as low as 0.3 microns can be stopped. I still am waiting for Niosh, the testing arm, and OSHA the implementation arm to verify. All I can say is I'm glad I didn't hold my breath.

The mystery testing company that has sprung HEPA and 0.3 micron screening is known as IEST. AKA The Institute of Environmental Sciences and Technology. I say mystery Org because I've not been able to track their origin, and know they are NOT part of the gubmit, because they have been around as long as HEPA has, and they don't show up in this registry.

I just keep wondering who gave them the MOJO to make up standards? Oh yeah the manufacturers they represent…..

Realistically a combo of both will land you the best filtration. The page Fresch posted is a great read on the road to understanding face masks, and the letter and numbers found on their packaging. As I said earlier depends on who's book. OSHA and Niosh are the governmental standards, their numbers don't change when talking about masks, or machines that filter, so I'll stick with theirs over Org's who have seemingly popped up, and made standards, and names of filtration, that has never gained any traction in real "standards"


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## clagwell (Dec 20, 2018)

> ... now suddenly we have HEPA, and particles as low as 0.3 microns can be stopped. I still am waiting for Niosh, the testing arm, and OSHA the implementation arm to verify. All I can say is I m glad I didn t hold my breath.
> 
> The mystery testing company that has sprung HEPA and 0.3 micron screening is known as IEST. AKA The Institute of Environmental Sciences and Technology. I say mystery Org because I ve not been able to track their origin, and know they are NOT part of the gubmit, because they have been around as long as HEPA has, and they don t show up in this registry.
> 
> ...


If by "suddenly we have HEPA" you mean as of 80 years ago then sure. HEPA filtration originated with the Manhattan project. Here's a good read on that. Besides the ASME test methods listed there, a lot of sources reference MIL-STD-282, which covers DOP testing.


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