Dust classes are often treated as a buying label, but they signal how you should plan and verify control on site. In simple terms: L Class is for lower-toxicity dusts, M Class is the expected minimum for most construction dusts, and H Class is for high-risk contaminants and sensitive environments. The class you pick should follow your COSHH assessment, not the other way around.

How to think about the classes

• L Class: suitable for nuisance dusts with lower hazard. Rarely appropriate for general UK construction because RCS and wood dust are common.
• M Class: the default for cutting, chasing, grinding, sanding and clean-up of mineral and wood dusts. Pair with tool shrouds and good housekeeping.
• H Class: for asbestos-related tasks, lead paint removal, mould remediation, pharma powders, or high-risk RCS indoors where consequences of escape are severe.

Make the class work in practice

• Capture at source: use the right shroud for your tool and keep the skirt sealed. Slow passes reduce escape.
• Control the room: in small or enclosed areas, deploy an air scrubber or negative air machine. Choose H14 filtration for fine/carcinogenic or respirable dusts.
• Housekeeping: never sweep. Vacuum settled dust with at least M Class. Seal bags before moving them through clean areas.
• Airflow under load: judge extractor performance with the tool connected. Use short, anti-static hoses and maintain filters.

MAXVAC systems can support this three-layer approach by combining tool-mounted extraction with portable air cleaners for enclosed spaces.

Examples that guide selection

• Plasterboard sanding in open areas: M Class extraction and good housekeeping.
• Concrete chasing in a flat: M Class at source plus H14 air scrubbing; consider H Class where risk is high.
• Lead paint removal: H Class with containment and controlled waste handling.
• Asbestos-related tasks: specialist asbestos procedures with H Class equipment and licensed methods.

Practical takeaways

• Use M Class as standard on construction; reserve H Class for high-risk substances and sensitive settings.
• Plan controls by layer: source, air, surfaces. Verify each layer.
• Record maintenance and checks as part of your COSHH documentation.

Choosing L, M or H is a control decision. If you control the process, manage the room, and clean without re-agitating dust, the class will deliver the protection it promises.