Dust Extraction Systems
Controls & Compliance · Controls & Compliance overview
Dust extraction systems are engineered to capture airborne dust at or near its point of generation, transport it through ducting, filter it from the airstream and discharge cleaned air safely. In UK workplaces they are one of the principal engineering controls under COSHH, and their effectiveness is judged by whether they keep worker exposure below the relevant Workplace Exposure Limit — not simply by whether they run.
What dust extraction systems are
A dust extraction system — most commonly referred to as local exhaust ventilation (LEV) in occupational hygiene — is a designed arrangement of capture hoods or enclosures, ducting, an air mover (fan), an air cleaning device (typically a filter or cyclone) and a discharge route. The system is sized and configured for the specific tasks it serves; an installation that works well on bag tipping may be inadequate for a high-speed sanding operation.
The reference UK guidance for LEV design, commissioning and ongoing examination is HSE HSG258 (Controlling airborne contaminants at work). Equipment supplied for COSHH-relevant processes is expected to be compatible with the principles in that document.
Where dust extraction is used
Dust extraction is used wherever a process releases dust faster than general ventilation can dilute it to acceptable levels. Common UK applications include:
- Woodworking — sawing, sanding, routing, planing, CNC machining and bagging stations.
- Construction trades — on-tool extraction for cutting, grinding and drilling masonry, concrete and stone.
- Manufacturing — powder weighing, mixing, milling, tabletting, packaging and bag emptying.
- Foundry and refractory work — shake-out, fettling, refractory installation.
- Welding and metalworking — fume capture at the torch and on the bench.
- Plastics, composites and recycling — granulation, dosing, shredding and conveying.
Capture, transport, filtration and discharge
Effective dust extraction depends on four engineering principles being achieved together. Failure in any one of them generally undermines the others.
- Capture velocity — sufficient air movement at the dust source, in the right direction, to draw the contaminant into the hood before it escapes into the workroom.
- Hood and enclosure design — hood geometry and position matched to the task, plume and operator working position; enclosure preferred where compatible with the work.
- Transport velocity — duct sizing maintained so airborne dust does not settle inside the duct (commonly 18–22 m/s for typical dusts, higher for sticky or fibrous materials).
- Filtration — collector type and filter media matched to the dust loading, particle size and explosibility characteristics, with adequate access for maintenance and bag/cartridge replacement.
- Discharge — cleaned air discharged to a safe location, with recirculation only where the substance, filtration performance and monitoring justify it.
Dust extraction versus general ventilation
Dust extraction (LEV) and general ventilation address different problems and are not interchangeable. LEV captures contaminant at source before it disperses; general ventilation dilutes residual contaminant across the workroom. For respirable dust and similar high-hazard particulate, dilution alone is rarely sufficient and is not normally an acceptable primary control under COSHH.
Where general ventilation supports a workplace with significant dust generation, its main role is to handle low-level residuals, manage temperature and humidity, and provide make-up air to balance the volume removed by LEV. It does not substitute for capture at source.
Common dust extraction problems
Dust extraction systems often fail quietly. The fan still runs, the cabinet looks intact, and yet exposure at the breathing zone is unchanged or worse. Recurring problems include:
- Hoods positioned too far from the source, or angled away from the dust plume.
- On-tool extraction with crushed, kinked or partially blocked hoses.
- Duct branches added over time without re-balancing system airflow.
- Filter cartridges or bags left in service beyond their effective life, raising pressure drop and reducing flow.
- Pulse-clean compressed air systems out of service or running at wrong pressure.
- Operators bypassing controls — running tools outside the hood, opening enclosures or disabling interlocks for speed.
- Discharge to roof level with short stacks that re-entrain into building intakes.
- No documented LEV thorough examination and test at the COSHH 14-month interval.
How dust extraction performance is verified
LEV performance is verified by a combination of airflow measurement (face velocity, capture velocity, duct traverse, static pressure benchmarks), qualitative observation (smoke or dust lamp visualisation), and exposure measurement at the breathing zone. Airflow on its own confirms that the equipment is moving air; it does not confirm that worker exposure is below the WEL.
COSHH Regulation 9 requires a thorough examination and test of LEV at intervals not exceeding 14 months, with the report retained for at least five years. The TExT report should be read alongside the most recent exposure assessment results.
Relationship with exposure assessment and control measures
Dust extraction is one engineering control within a broader dust control system. Its effectiveness should be judged against the outputs of a dust exposure assessment and considered alongside source control, suppression, housekeeping and RPE. A new or upgraded extraction system is most defensible when before-and-after exposure data demonstrates the expected reduction at the breathing zone.
Frequently asked questions
Is LEV the same as dust extraction?
In UK occupational hygiene, local exhaust ventilation (LEV) is the formal term for engineered systems that capture airborne contaminants — including dust — at source. Dust extraction is the everyday term used for the same arrangement when the contaminant of interest is solid particulate.
How often does dust extraction need to be tested?
Under COSHH Regulation 9, LEV used to control hazardous substances must receive a thorough examination and test at intervals not exceeding 14 months. The report must be kept for at least five years and made available where required.
Can extracted air be returned to the workshop?
Recirculation of filtered extracted air back into a workroom is sometimes done in practice but is only acceptable where the substance, filtration performance and continuous monitoring justify it. For carcinogens and many high-hazard dusts, recirculation is not appropriate without specific assessment.
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