M Class dust extractors are designed to control medium-hazard dusts typically found on UK construction sites. Under COSHH, employers must reduce exposure to as low as reasonably practicable. HSE guidance generally expects M Class as the minimum for most site dust control, particularly where respirable crystalline silica (RCS), wood dust, and cement-based materials are present. Used well, they protect health, speed clean-up, and reduce cross-contamination.

When you need M Class

Choose M Class when your work creates fine, harmful dusts but does not involve high-risk contaminants such as asbestos or significant lead paint removal. Common scenarios include cutting, chasing, grinding, or sanding materials like concrete, brick, mortar, tile backer board, hardwoods and MDF, as well as cement and plaster residues. Outdoors, water suppression helps; indoors, capture on the tool and good housekeeping are essential.

Set-up that actually works

• Capture at source: use purpose-made shrouds and tool-mounted extraction on grinders, saws and sanders. Keep the skirt sealed to the surface.
• Airflow under load: assess performance with the tool connected, not free-air figures. Short, smooth, anti-static hoses reduce losses.
• Filter management: use auto filter cleaning if available and fit fleece bags or pre-filters to slow filter loading and maintain consistent suction.
• Housekeeping: avoid sweeping and compressed air. Vacuum settled dust with an M Class industrial vacuum; log bag changes and seal waste before removal.
• Room control: in small rooms or basements, consider an air scrubber or negative air machine to manage airborne particulate. Use H13–H14 filtration where fine or respirable dusts are a concern.
• RPE and method: wear suitable RPE alongside extraction. Use slower passes and steady feed to reduce dust escape.

Equipment from manufacturers such as MAXVAC can integrate tool shrouds, M Class extraction, and room air filtration for a layered approach.

Quick compliance context

HSE EH40 sets the UK Workplace Exposure Limit for RCS at 0.1 mg/m³ (8-hr TWA). Wood dust WELs are 3–5 mg/m³ (inhalable). M Class helps you meet these duties when combined with effective methods and supervision, recorded under your COSHH assessment.

Verification on site

• Do a simple capture test: run the tool with extraction; check for visible escape at the shroud edge and adjust technique or seals.
• Spot-check with a particulate monitor where available, especially in confined areas.
• Keep a maintenance log: filters, gaskets, hoses and bags inspected and replaced as needed.

Practical takeaways

• Use M Class as the default for construction dusts including RCS and wood.
• Prioritise tool-mounted capture, then room control, then housekeeping.
• Judge airflow under load and manage filter loading to keep performance steady.
• Never sweep; vacuum with M Class and seal waste immediately.

M Class extractors are the practical standard for most site activities. When materials or conditions increase risk, step up the controls (air scrubbers, better enclosures, tighter methods) and escalate to H Class where the dust or task demands it.