Recommended respirator mask for cutting MDF

(Ryan) #1

I’ve got an enclosure that I keep the Shapeoko in along with a dust deputy and I work mostly in my backyard. However, today was the first time I cut MDF and my dust shoe wasn’t able to do it’s job properly. So there was MDF dusts everywhere (inside the enclosure) and cleaning up once the job was done was not easy.

My question is, will my 3M N95 approved respirator mask be good enough to use when cleaning up MDF dust?

I also have another respirator mask that I have stored away but only used when I’m spray painting.

Should I use this instead when cleaning up MDF dusts? I wasn’t sure if an aerosol respirator mask was applicable for wood dusts.

(Mark Bellon) #2

The joke goes that MDF is sawdust and glue… and that is close to the truth. The “glue”, when machined, can range from severely toxic to just an irritant. Unless you live in the CA, there is no insurance you’re working with the low toxicity stuff. Some of the MDF in the market comes from China and has been found to contain carcinogens, mutagens, and teratogens. There are issues of chemical exposure with MDF and other materials, it’s not just about the particles.

MDF is an example of a friable (easily crumbled) material. When friable materials are machined, they yield particles that can very dangerous to your health. Other problematic materials are FR4, carbon composite, Garolite, and fiberglass. Many hardwoods - especially exotics - can also be very nasty.

Oh, also anything with Beryllium (or Plutonium) in it - SUPER NASTY!

The N95 is not sufficient. You need a respirator that has a positive seal and uses HEPA filters or equivalent. Simple saw dust masks don’t come anywhere near to being safe.

Using a mask is good but… the MDF particles get everywhere, contaminating the room, your clothing, your hair and so forth. You land up carrying the nasty particles with you, exposing yourself and others.

To be safe, you need a sealed enclosure and a vacuum system that pulls enough air to ensure “lifting”. Your hose is clearly insufficient.

It’s all about limiting exposure. Anything is better than nothing and perfection is the enemy of good enough. Most CNC purchasers do not budget anywhere near enough to safely use their machine. The good news is a few changes and you can dramatically reduce your exposure. We can work within most budgets; some creative solutions can be most effective.

I can help you offline, message me. You can also look up my postings on air and ear safety. I’m about the only person who uses the work “friable” so that will help locating my air safety postings.

Here is a good place to start:



Don’t forget your hearing exposure. Without the proper protection, the prolonged exposure is ear damaging.

(Jude Marleau) #3

Just googled it…“chronic life-threatening allergic disease in some people called berylliosis”, wow… when an element has a specific disease named by the name of the element than holy cow that has to be bad stuff. Thanks Mark, something else important enough to change behaviors overall, time to upgrade dust masks. I’m going to suggest that mdf dust causes MDFiosis and requires a respirator mask even when vacuuming up the area, (not trying to be humerous). My next shop upgrade may be exhausting the shop vac below the floor to the crawl space (not connected to house) so not to inflict hazards to outside (let the snakes and rodents deal with it). You are a terrific source Mark, I appreciate your postings and points of view. Jude

(Mark Bellon) #4

Just googled it…“chronic life-threatening allergic disease in some people called berylliosis”, wow… when an element has a specific disease named by the name of the element than holy cow that has to be bad stuff.

History: the first two heat shields for the Mercury space capsule used Beryllium.

About 10% of the people are hyper sensitive to Beryllium and can die from very, very small exposure… and it’s easily airborne. The good news is that it very hard to come by… except if you machine copper for electronics. Beryllium is used to strengthen Copper. If you’re going to machine Copper, insist that the supplier supply documentation that it is pure Copper - no Beryllium.

As I said, our concern is cumulative exposure. Anything we do to decrease our exposure is a good thing. Ideally, we have an sealed enclosure, an dust collector with sufficient ability to lift, tubing sufficiently large to ensure sufficient air flow at the dust head, and a dust head with a good brush or skirt.

A common mistake is the tubing - too small, too long, too many bends - but thankfully this is something that is usually easy to fix and relatively inexpensive to remedy. It’s also important to choose conductive tubing - anti-static - as moving particles generate an electric field and this can cause clumping and other flow problems. On an industrial scale, lack of static treatment can cause explosions. I kid you not. Massively powerful ones.

A dust collector - a vacuum - can be a real challenge. How they work, how they filter, and where the discharge air goes are all issues. Because filters are expensive, we usually add a dust separator - commonly a cyclone - to remove as much as we can before the dust collector.

Where the exhaust air goes is also an issue. There are two common solutions:

  1. Exhaust dumped inside (with humans)

    One needs a HEPA filter or equivalent (0.5 micron).

  2. Exhaust the air outside.

    Just be sure there is no easy way for the air to get back inside (like a nearby window!).

    Using this solution, it’s a good idea to have an accessible 5 micron, washable cloth filter/bag on the discharge. One tends to collect “snow”.

    Check with neighbors as you’re piping sound outside and the output can be loud.

The common “shop vac”, even with a dust separator, can actually increase your exposure to the fine, damaging particles.


I use the 3M 6000 line of masks (6291 or 6391; depends on the shape of your face) when I use one (usually when I’m emptying my dust collector and/or separator). Even so, I stand up wind so as to avoid getting particles on my cloths and in my hair.

If you’re vacuum system is well designed there should be virtually no visible dust inside your enclosure. Using a mask for vacuuming out your enclosure is a good idea, even if things are near perfect. Remember that it’s not just the particles themselves, it’s also the chemicals (or viruses!) in the material.

(Jude Marleau) #5

I’ll repeat it, Thanks Mark you are a terrific source and I appreciate your postings and point of view, also for specifying the mask you use. And the shop vac exhaust frustrates me to no end as if I inadvertently rotate the unit as I vacuum and the exhaust blows toward what I’m vacuuming than what I’m vacuuming gets blown worst than sweeping. All thoughts point towards a bigger dust system, you really can’t over do a collection system, I guess.

(Mark Bellon) #6

A “good enough” dust collector, a dust separator, and an exhaust system doesn’t have to cost the world. If one can exhaust the air outside, a cyclone and a good quality shop vac - one that is SEALED - is sufficient provided there is an anti-snow bag. This avoids dumping the air with humans and even meets the strict EPA rules.

There is another reason for an anti-snow bag - termites! Lovely, easy to digest wood particles are termite bait.

Inside, we need HEPA filters. These are somewhat expensive. A dust separator (e.g. a cyclone) is a necessity unless you’ve got nearly unlimited funds for filters.

Properly tubing the vacuum system is a bit of a challenge but far from impossible or difficult to understand. One needs the largest tubing they can use and run it for the shortest distance they can. I can discuss specifics should people wish to know. A good rule of thumb is no less than 2.5"; 4" is necessary to near perfection.

Like a level 4 clean room - where they handle Ebola and other nasty viruses - we need to room/enclosure to be at negative pressure so that any leak is into the enclosure, not out. An enclosure for a CNC machine should be caulked/sealed and use door seals - weatherstripping is good enough. Make sure that an inlet for air going into the enclosure is at least as large as the one where you’re pulling the air out.

At least one person in this forum had their stuffy noise and near allergic symptoms disappear almost immediately after properly handling their air.

I want to repeat that there are many things that can be done without spending a huge amount.


(Art Peters) #7


I too want to thank you for information… I’d like to seek your opinion as to the differences between
The 30 6000 and 7500 series respirator masks. Also, which filter do you suggest / use?



(Mark Bellon) #8

I’d like to seek your opinion as to the differences between the 3M 6000 and 7500 series respirator masks.

I’ve used 6000 and 7000 series 3M masks. I usually suggest the 6000 series due to the lighter construction and less face cover. Many people are uncomfortable in masks and the lighter, more open design is better received. The 7000 series masks are generally half face masks… more face coverage and potentially a better seal… but more likely to make some uncomfortable.

My experience is that the 6000 series is fine for light use, the 7000 series for longer use… provided one tolerates them well. The 7000 series filters are larger - cartridges really - and the 7000 series is a bit better at avoiding glasses fogging.

Also, which filter do you suggest / use?

3M has a zillions filters so filter choice can be complicated. You can ignore the chemical filters for CNC work, the particulate filters are sufficient. One wants HEPA filter performance or better (0.5 micron). As I recall, there is a new standard, NIOSH, that is as good or better than HEPA. That would be the P100 particulate filters.

(Art Peters) #9


Thanks, given what you have said, I think that I’ll try the 7000 series of the 3m variety based on the fact that my glasses tend to fog with just the paper masks, and I tend to put a mask on and keep it there for hours at a time…

Also, if I might ask, my shopvac has what it claims is a hepa filter in it, but only seems to cost about $10 - $15, it is an old ~20yrs shopvac so either I recall incorrectly, or they are no longer made, if you were to recommend a vac, what direction would you go. For my situation right now, it is only the shapeoko, but I can envision a more complete shop in the future … Oh setup is in a dedicated pole barn

73 …/Art

(Art Peters) #10

Oops, sent too quick, I did add a dust deputy, made a huge improvement in conjunction with my suckit…


(Mark Bellon) #11

Oops, sent too quick, I did add a dust deputy, made a huge improvement in conjunction with my suckit…

A dust separator, the Dust Deputy being a fine example, can reduce the particulates that get to the dust collector by 95%or more. It’s a necessity to avoid going through HEPA filters quickly. A HEPA filter is necessary when the exhaust air is dumped inside with humans.

My shopvac has what it claims has a HEP filter in it, but only seems to cost about $10 - $15,

The cost is a bit suspicious, HEPA filters are usually more expensive. One possibility is that they are small or lack the large capacity for particles that the more expensive types do.

it is an old ~20yrs shopvac so either I recall incorrectly, or they are no longer made,

The good ones last… :slight_smile:

if you were to recommend a vac, what direction would you go.

That depends on several factors, including budget.

For my situation right now, it is only the shapeoko, but I can envision a more complete shop in the future …

If one is investing in the future and is thinking that they want excellent dust collection now and room for a larger machine one should purchase a formal, industrial dust collector. Surprisingly, they aren’t that expensive. This should be coupled with a formal, industrial dust separator.

When using this approach, one wants a dust collector that uses 4" or larger tubing and 1000 CFM or more of air flow. The dust separator should also use 4" or larger tubing. Then run the largest tubing you can for a short as possible. Only when necessary adapter it down. Under all circumstances the tubing should not be less than 2.5" when collecting to the dust head.

If you want to discuss the specifics of this approach, let me know. The budget is higher than a simple shopvac but this is a one time investment. The only throw away is the last section of tubing. Overkill for now but room for the future.

If you’re not shooting for that, then we’re into dust collectors and separators that should use a minimum of 2.5" tubing. We want a huge amount of air flow. if we can dump the exhaust air outside we don’t need a HEPA filter. Otherwise (air is dumped inside) we need a HEPA filter.

An excellent all-in-one choice is Festool. They are rated for Asbestos removal! They aren’t cheap but boy they work well. Bias statement - I use Festool for my small CNC work. Excellent choices are also offered by Dustless Tools, Rigid, Nikro, and Vacmaster… and there are others.

For larger machines, I use the larger approach. For those with a limited budget, hybrids can be designed.

A significant issue with dust collection is NOISE. A CNC machine in an enclosure is considerably quieter than the dust collector… which means we need to design an enclosure for the dust collector too!

Another significant issue is the quality of tubing. Conductive (“anti-static”) is called for, as is proper grounding. Thankfully, there are some good sources for this at relatively low cost.


(Art Peters) #12


Thanks for that information, right now, I am going to incorporate the upgraded 3M masks and make an effort to vent the shopvac outside, perhaps in the spring, I’ll seek a more robust dust collection solution, and ping you for advice, for features / brands.

Really appreciate your time and insights.


(Art Peters) #13


Thanks again for your recommendations. I just received my 3M 7000 mask, not only does it fit well, no fogging of glasses!!! Yea