The Difference Between L, M, & H Class Vacuums; Which One Is Right for You?

If you've found this article, chances are you're asking yourself “what’s the difference between L-Class, M-Class, and H-Class Vacuums? If this isn't the first stop on your research journey, you'll have seen a lot of varying information, even about technical classifications. There are a few reasons for this; Silica Safety is a hot topic at the moment. Many companies are writing online articles in a bid to capture some of this new audience. These include residential vacuum companies and businesses that use industrial vacuums in their operations. On top of this, there are still many out of date articles in circulation, that reference old & un-current codes of practice.

At All Preparation Equipment,

  • We work closely with Workplace Health & Safety.
  • We're partnered with Dust Control, a world leader in manufacturing Dust Extraction Systems for all industrial applications including Military, Aviation, Construction, Food and Manufacturing.
  • We are also a leading construction industry supplier of H-class vacuum systems in Australia.

It doesn't end there though, we always endeavour to have the information provided in our articles vetted before posting to ensure its accuracy so we're giving nothing but the best advice. 

An Overview of the Different Types of Vacuums 

There are many different types of industrial vacuum out there. Things like filtration levels and size mean each is suited to a different task. The class rating (L, M & H) has nothing to do with the Vacuums ability to pickup dust. The rating is to discern the Vacuum's ability to filter out different sized particles. Without that filtration, the particles would just be recirculated back into the air. Hazardous particles, like respirable silica dust and asbestos, can stay in the air for more than 40 hours due to their size, so filtration is ultra important when working with hazardous particles.


L M H-Class Vacuum Ratings

What does “L,” “M,” and “H” Class Actually Mean?

If we think in terms of real-world applications, we can summarize each of them as follows.

  • L-Class (light hazard) - Filter efficiency of 99% - Suitable for home cleaning or for the odd DIY home renovation job.
  • M-Class (medium hazard) - Filter efficiency of 99.9% - Suitable for a hobbyist workshop, or for plastering on-tool extraction.
  • H-Class (high hazard) - Filter efficiency of 99.995% - The minimum for working with hazardous materials like silica dust, asbestos & lead paint.

Unfortunately, not all H-Class vacuums are created equal, nor do they even filter the same size debris. The rating is only the minimum required and many of the particles they're designed to filter, do exist, smaller than the rated filter ability. Unless your retirement plan includes medical expenses, I'd be reading on to really consider the implications of this. 

L-class for plastering

L-Class Vacuums - Why You Probably Don't Want One.

An L-Class vacuum is only suitable when working with lightly hazardous particles. Dust, dirt, and debris fall into this category. It is not a suitable vacuum to use whenever hazardous materials are involved such as mould spores, silica or asbestos. Those require a minimum of HEPA-filtration for removal. (mould spores, actually require an Ozone generator on top of HEPA filtration)

 For a vacuum to gain an L Class rating, at the time of testing, it must filter at least 99% of a micron 0.3 µm. Particles of this size include; general dirt and dust, plaster dust, some aluminium dust, and some wood dust. 

The filter for an L-Class machine is E12 Sub-HEPA (ISO 25E). This classification replaces the older and now redundant H12 rating. 

 No testing is required in order to maintain an L-class rating. Also, most L-class machines are manufactured by jack of all trade companies rather than specialists in dust extraction. The likelihood of an L-class vacuum maintaining sufficient filtration to keep its rating for long is tiny. For this reason, amongst others, we do not recommend L-class machines at all for construction work.  

m-class vacuum for plastering

M-Class Vacuums - The One You Should Be Using for Light Hazards.

Technically, an M-Class vacuum is suitable for use with medium hazardous particles such as concrete dust, wood and MDF dust. We do not recommend M-class for use with Silica dust. This is because Silica dust comes in various sizes, some small & some big. Respirable Crystalline Silica (RCS) Dust on the other hand, is very small. In-fact, RCS is so small that the human eye cannot see it. M-class filtration is not capable of filtering RCS despite currently being allowable to use with Silica under certain circumstances. It gets worse though, if using an M-class vacuum with silica, the operator is likely to believe they are safe, when they aren't. This is because they can't see the dangerous particles being pumped back into the air that they are breathing while using an M-Class vacuum.

For a vacuum to gain an M Class rating, at the time of testing, it must filter at least 99.9% of a micron 0.3 µm in diameter. Particles of this size include; aluminium dust, wood dust and MDF dust. 

Filter classification for an M-class machine is E13 HEPA (ISO 35H). 

Maintaining an M-class rating will require annual testing when used in construction. We would only recommend them to be used in place of an L-class machine. This way, you're exceeding the "Minimum" filtration required. Plus you are using a machine that's been built with the idea that it will need annual testing to keep its rating. Of course, H-class would still be better if you value your health, regardless of the hazard level of the materials you are working with. Remember that at one point, Lead, Silica and even Asbestos were thought to be safe to work with. Who knows if there are other materials currently considered safe, that are actually extremely dangerous.


h-class vacuums for construction industry

H-Class Vacuums - The Minimum Safe Option

Technically any H-Class vacuum is suitable for use with highly hazardous particles such as respirable silica dust, asbestos and lead. We recommend digging a little deeper before committing to just any H-Class vacuum, though. 

For a vacuum to gain an H Class rating, at the time of testing, it must filter at least 99.995% of a micron 0.3 µm in diameter. Particles of this size include; asbestos, RCS, Lead etc 

Filter classification for an H-class machine is E14 or E15 HEPA (ISO 45H, H15). 

To maintain an H-Class rating, the vacuum needs to have the HEPA filter replaced and then pass a DOP test every 12 months. At All Preparation Equipment, we have an in-house DOP testing facility. DOP testing gives us a unique insight into H-class vacuums & air purifiers that normal resellers just don't see. Testing so many different H-Class vacuums, made a few things quite obvious, mainly that not all H-Class Machines are created equal. Build quality not only affects the longevity of the machine, but also the ability for the vacuum to filter reliably. Often these cheaply made flimsy plastic machines fail to seal sufficiently to pass the test. To fix this, we will need to disassemble & manipulate the casings, filters and seals multiple times. Without this, they usually only achieve L or M class filtration since the poor seal allows hazardous particles to bypass the filters inside the vacuum. When we do finally get these cheaply made H-class vacuums and air purifiers to pass the test, they only just scrape by. Even after all this, it's likely the seal required to achieve that H-class level of filtration will fail as soon as it's knocked around a little. We choose to partner with DustControl, since these heavy duty Swedish made systems are mostly steel, they do not suffer the sealing issues we find in most other brands. It's a no-brainer really, unless your retirement plan includes medical expenses and/or you don't care much about burdening your loved ones. You'll want your H-class vacuums to provide better than H-class level filtration consistently, so that they protect your health.

Plastic vs steel h-class vacuums


With so many varieties and classifications of vacuums available, there is no one-size-fits-all approach to the perfect vacuum cleaner. In our opinion, an L-Class Vacuum is really only suitable for home cleaning and the occasional DIY job. An M-Class Vacuum should be reserved for any situation that usually calls for an L-class machine. And an H-Class Vacuum should be the bare minimum for any operation where the safety of yourself and your workers is important. 

But there's more to vacuum safety than just the ability to filter the air. Some other important things to consider are;

  • Does the vacuum incorporate a Longopac continuous bag system? If not, you're going to be exposed to hazardous particles at each bag change. You'll also need to wear your respirator each time you change the bag. (These small exposures are when workers are most likely to ignore their PPE causing health issues in the long run) 
  • Can the vacuum create enough airflow and suction to safely extract the hazardous particles from the tools and machinery you're using? To get an answer to this requires careful scrutiny of the figures displayed. For example, it's possible to manipulate these tests to display unrealistic figures. Some manufacturers will remove the filters when testing, some will remove the hose, some will measure directly at the motor/fan. The only test that matters is the one taken at the end of the hose with all the filters installed. That is how the vacuum will be when you are actually using it. 
  • Does the vacuum have a filter cleaning mechanism? If so, how good is it? Dirty filters will reduce airflow and suction, so it’s imperative that they can be cleaned regularly without pulling the machine apart. It's not practical to pull the machine apart every 20 mins to clean the filters, and it's also dangerous to expose yourself to the hazardous particles you're trying to filter out. 
  • How many square meters of surface area is the Fine filter & HEPA filter? The larger this area, the longer the vacuum can keep its performance between filter cleans and the longer they will last before they require replacing.
  • Is the hose anti-static or better? Cheap hoses will collect static electricity which attracts debris. Once the vacuum is turned off and that static electricity dissipates, the debris will fall off the hose, re-contaminating the floor and air.
  • What is the servicing and after sales support like? Time is money, so there is no point investing in a machine that leaves you stranded for 6 weeks every time it needs a service. At All Preparation Equipment, we usually have same day turnaround on services and 1 week or less for repairs. Plus, you can hire a similar machine from our Brisbane office to eliminate downtime completely.
  • What is the warranty with the machine and more importantly, does it cover commercial use? Dust Control Vacuums have an industry leading 24month warranty even for commercial use. To maintain that warranty, all you need to do is follow the filter replacement schedule. 

If you'd like to invest in quality, talk the team at All Preparation Equipment about which sized Dustcontrol vacuum is right for your operation. - 1800 422 992. 

Otherwise, drop into our Brisbane or Sydney store and one of our team can show you what makes Dustcontrol the obvious H-Class choice in person. 

Author: Elliot Moss - All Preparation Equipment

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