Replacing Air Filter Media for Microclene & Thor Machines

Your Microclene Still Works — Here's How to Keep It Running

If you own a Microclene air filter, here is the good news: your machine does not need to be retired. Thousands of these units are still running in workshops across the UK, and they can keep running indefinitely with the right replacement media.

Microclene machines are no longer in production, but Thor Filtration took over in 2017. Thor had always been the metal fabricator for the entire Microclene range. They use all the same components, including the original Swiss-made motor, so these are not generic copies. They are the same machines under a new name.

Thor replacement filter media is fully cross-compatible with legacy Microclene units. This guide will help you identify the right replacement media for your machine, understand when to replace it, and know why it matters for your health.

Microclene to Thor: The Complete Filter Media Compatibility Guide

If you know your old Microclene model number, the chart below gives you the current Thor part number to order. These are the references we use at CXS Tools, and they are the standard ordering codes across all stockists.

• TF250 — fits Microclene MC100 and MC200
• TF450 — fits Microclene MC400 and MC450
• TF470 — fits Microclene MC420
• TF810 — fits Microclene MC760
• TF1250 — fits Microclene MC1200
• TF1260 — fits Microclene MC1210
• MC780 / MC1000 media — fits those legacy Microclene units directly (including the very early MCF100 and MCF200 models)

Even if your machine dates back well before the 2017 changeover, you are not left without options. The original Microclene designs were created by Acrol Limited, and Thor carried that engineering forward without modification.

To confirm you have the right model, here is a quick guide to each machine's form factor and workshop suitability:

• TF250 (MC100/MC200) — Bench or shelf-mounted. Suited for small workshops up to 22 m³.
• TF470 (MC420) — Ceiling-hung unit. Designed for single-garage workshops up to 40 m³, with an airflow rate of 400 m³/hour.
• TF810 (MC760) — Tabletop or bench-mounted. Covers double-garage workshops up to approximately 78 m³, filtering 750 m³/hour.
• TF1260 (MC1210) — Ceiling-hung. For larger workshops up to 120 m³.

If you are unsure which model you have, check the label on the back of the unit, or give us a call. We can usually identify it from a quick description or photo.

What the EU4/G4 Filtration Standard Actually Means for Your Health

Thor and Microclene filter media is made from polyvee glass, manufactured to the EU4/G4 standard (classified under EN 779). In practical terms, the media captures 95% of dust particles at 2 microns or larger, 80% of particles down to 1 micron, and 65% of particles as small as 0.4 microns. These numbers matter because particles below 5 microns are classified as respirable dust. They bypass your nose and throat and penetrate deep into your lungs, where they cause the most damage.

The health stakes are real. The International Agency for Research on Cancer (IARC) classifies wood dust as a Group 1 human carcinogen, with strong evidence linking occupational exposure to adenocarcinoma of the nasal cavities and paranasal sinuses. Carpenters and joiners are approximately four times more likely to develop occupational asthma than other UK workers. Research published in Occupational Medicine in 2023 estimates global asthma prevalence among woodworkers at 6–18%.

In our experience advising woodturners over the past 25 years, many people underestimate how much fine dust a sanding session produces. Fine sandpaper on beech, for example, generates a respirable dust fraction of around 5%, compared to just 0.6% with coarse grit. That fine dust is almost invisible, yet it is the most hazardous.

The HSE's 2022/23 inspection programme found that 78% of woodworking businesses were not compliant with dust protection requirements, resulting in 402 enforcement actions. These figures should concern professionals and hobbyists alike.

Fine dust particles can remain suspended in workshop air for days after you finish working. Dust extraction at the tool captures the bulk of material, but it does not clear the ambient air. An air filtration unit running in the background is the essential second layer of protection, cleaning the air you breathe long after the lathe or sander has stopped.

Standard vs. Carbon Filter Media: Which Do You Need?

The standard white polyvee glass media is designed to capture particulate dust. For the vast majority of woodworking, woodturning, and sanding applications, this is the correct choice. It handles the fine dust that your extractor misses, effectively across the full particle range described above.

Carbon filter media variants are available for certain models, specifically the MC760/TF810 and MC780/MC1000. These contain activated carbon that absorbs airborne fumes and vapours in addition to trapping particles.

If you do any pyrography in your workshop, carbon media is worth serious consideration. Burning wood produces chemical fumes, not just particles, and a standard particulate filter will not capture those. The same applies to airbrushing, spray finishing, and working with solvent-based products. In these scenarios, carbon media provides a meaningful extra layer of health protection.

Most users are not aware this option exists. The rule of thumb is straightforward: if your work is purely mechanical (turning, sanding, routing, planing), standard media is correct. If heat or chemicals are involved in any part of your process, carbon media adds genuine value.

When to Replace Your Filter Media (And How to Tell It's Time)

Thor and Microclene filter media should be replaced every 200 to 400 operating hours, depending on your dust load and how frequently you use the machine.

To make that practical: a hobbyist working around 4 hours per week should expect to replace media roughly every 12 to 25 months. A professional running the machine daily could need new media every 2 to 4 months. These are broad ranges because a heavy sander generates far more dust than someone doing light finishing work.

Between replacements, you can extend the media's service life with simple maintenance. Periodically vacuum the filter surface lightly, or carefully tap it out to dislodge accumulated surface dust. This helps maintain airflow but does not replace a scheduled media change. The internal fibres become progressively loaded with fine particles that vacuuming cannot reach.

Here are the signs that your filter is overdue for replacement:

• The media looks visibly grey or clogged when you inspect it
• Airflow from the machine has noticeably reduced
• The motor sounds louder than usual, working harder to pull air through
• You notice a persistent dusty smell in the workshop even while the unit is running

Replacing the media rather than the whole machine is both the cost-effective and environmentally responsible choice. A well-maintained Thor or Microclene unit can last decades. The media is the consumable; the machine is built to endure.

Choosing the Right Size Unit for Your Workshop

The general rule for ambient air filtration is 10 air exchanges per hour. Multiply your workshop volume in cubic metres by 10, and you have the minimum airflow rate your unit needs to deliver.

For example, a 35 m³ single garage needs at least 350 m³/hour of airflow. The TF470, rated at 400 m³/hour, is the right fit. A 70 m³ double garage needs at least 700 m³/hour, making the TF810 at 750 m³/hour the appropriate choice.

If you are replacing media on an existing machine, this is a good moment to check whether your unit still matches your space. Workshops grow over time, and if yours has expanded, an upgrade may be worth considering. CXS Tools stocks Thor Filtration replacement filter media for all compatible Microclene and Thor models. If you are unsure which media your machine takes, call us or drop us an email. We are happy to help you identify the right part.

Keep Your Machine Running, Keep Your Lungs Protected

If you own a Microclene machine, you have a direct and affordable path to keeping it running: Thor replacement filter media, made to the same specifications, in the same Hampshire factory, by the same team that built the originals.

With wood dust classified as a Group 1 carcinogen and HSE enforcement actions on the rise, regular filter media replacement is not optional maintenance. It is a health safeguard. An estimated 11,000 lung disease deaths each year in the UK are linked to past occupational exposures. The dust you breathe now has consequences that may not show up for years.

Use the compatibility chart above to identify your media. Calculate your replacement schedule based on your hours of use. Order before your filter becomes a liability rather than an asset.

CXS Tools is run by a woodturner with over 25 years of hands-on experience in the workshop. We know these machines because we use them. If you have any questions about your Microclene or Thor unit, or need help choosing the right filter media, get in touch by phone or email. We are always glad to help.