Explained: M Class Dust

Fact: At the moment, it’s very hard to properly understand and appreciate the world of dust safety. A large reason for this is that it’s based on ‘lots of very scientific testing done measuring things the naked eye can’t see’. The health symptoms can sometimes take a long time to show as well. No wonder it’s tough to wrap the brain around it all!

So, to help demystify things, let’s keep things simple for once and answer four easy questions:

  1. Why is dust dangerous to our health?
  2. What is a dust class and how are the classes set?
  3. What is M Class dust specifically?
  4. What is required of a dust extractor to be approved for M Class dust?

Question 1 – Why is dust dangerous to our health?

Dust is dangerous because it can travel into our airways and penetrate the tissue in our lungs, which puts us at risk of developing various diseases. The chemicals in the more harmful dusts are basically just poison to our bodies meaning we struggle to fight them off. You can read (a lot) more on the dangers of dust in this publication by the World Health Organisation.

Question 2 – What is a dust class and how are the classes set?

A dust class is just a rating of how dangerous certain types of dusts are to humans. They are set based on a) the chemical composition of materials, b) the size of the dust particle, and c) exposure limits. The general rule is the smaller the dust particle, the more dangerous it is because it can travel further into our system and lodge itself in our tissue. And it’s pretty obvious that the longer we’re exposed to such dusts, the greater the risk.

There’s an international standard (IEC 60 335-2-69 if you want to look it up) that categorises all types of dust into three main classes; L, M and H. You can read more on dust classes here.

Question 3 – What is M Class dust specifically?

It goes L > M > H (lowest to highest) in terms of risk rating, so M Class dust is mid-level. That doesn’t mean it’s not as dangerous as you think though. It includes dust from hard woods, board materials, some paints, concrete and bricks. M Class also includes something you’ve probably heard of, crystalline silica dust, which is found in sand, stone, concrete and mortar. 

Question 4 – What is required of a dust extractor to be approved for M Class dust?

All M Class dust extractors have passed testing at the point of manufacture that proves they capture no less than 99.9% of dust. For example, here’s the certification document from Germany for the Festool M Class dust extractors. This means you can’t ‘upgrade’ a dust extractor from one class to another. 

What’s the go for M Class then?

You’ll find that suction levels between L and M Class extractors are very similar. An M Class extractor however will have superior filtration and a flow sensor / alarm that alerts the user to a drop in suction rate caused by things like a blocked hose or full dust bag.

So, to put it simply, you take an L Class dust extractor with a HEPA filter, add a flow sensor / alarm, and you’ve got an M Class dust extractor.

Or, for all Autoclean dust extractors with a high performance filter, add a flow sensor / alarm, and you’ve got an M Class dust extractor.

However, for THE BEST performance, there are a few other functions you’ll want. They are:

  • ‘Auto-start’ and ‘delayed shut-off’ for power tools, which saves you turning two things on at the same and ensures ALL dust is properly and efficiently captured
  • Automatic filter cleaning that keeps the filter clear and maintains maximum performance while preventing premature motor burn-out
  • Capability for wet and dry materials, but you need to change or remove the filter and dust bag depending on the material

That’s M Class explained!

So, that’s it. If you have any questions, please feel free to get in touch and we’ll answer what we can or point you in the right direction. Please share this article with anyone you think may find it helpful as well.

Original article by Festool Australia.

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