COSHH · Mandatory · Pre-Construction
COSHH Assessment — Wood Dust
This COSHH assessment covers wood dust exposure from cutting, sanding, routing, and planing timber. Hardwood dust is a known carcinogen and softwood dust causes respiratory sensitisation. The workplace exposure limit for wood dust is 3 mg/m3 (hardwood) and 5 mg/m3 (softwood). On-tool extraction and LEV systems are the primary control measures.
Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. COSHH Regs 2002 / WEL remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.
| WEL reduction | The workplace exposure limit for all wood dust was reduced from 5 mg/m3 to 1 mg/m3 in 2020, reflecting updated evidence on cancer and respiratory disease risk |
| Hardwood carcinogen | Hardwood dust is classified as a Group 1 carcinogen by IARC. Causes nasal and sinonasal cancer with a latency period of 30 to 40 years |
| Softwood | Softwood dust is a respiratory sensitiser capable of causing occupational asthma. Once sensitised, even very low subsequent exposures can trigger severe asthma attacks |
| High-risk tasks | Machine planing, routing, sanding (especially orbital and belt sanding), sawing, turning and drilling. Hand tool work generates significantly less dust but is not zero-risk |
| LEV | On-tool extraction using an H-class vacuum is the primary engineering control. LEV systems must be examined and tested by a competent person at least every 14 months |
| Enforcing authority | Health and Safety Executive (HSE) |
1. The Wood Dust Hazard on Construction Sites
Wood dust is one of the most widespread occupational health hazards on construction sites. It is generated by every carpentry, joinery and fit-out activity that involves cutting, planing, routing, sanding, drilling or shaping timber. The health effects of wood dust exposure are severe, well-documented, and in the case of nasal cancer caused by hardwood dust, irreversible and frequently fatal. Despite this, wood dust exposure on construction sites remains poorly controlled in many cases.
The workplace exposure limit for all wood dust (hardwood, softwood and wood-based panel products) was reduced from 5 mg/m3 to 1 mg/m3 in January 2020. This five-fold reduction reflected the weight of evidence that the previous WEL did not adequately protect workers from the cancer and respiratory disease risks of wood dust exposure. At 1 mg/m3, the WEL is now at a level where many common woodworking activities carried out without extraction will exceed the limit — machine planing, routing and sanding in particular generate dust concentrations that are many times the WEL within minutes of starting work.
The health effects differ between hardwood and softwood species, and the COSHH assessment must distinguish between them because the control requirements differ accordingly.
Hardwood and softwood present different health risks — the COSHH assessment must address both
Hardwood dust (oak, beech, iroko, mahogany, teak, walnut, ash, elm, birch and all other deciduous species) is classified as a Group 1 carcinogen by IARC. It causes adenocarcinoma of the nasal cavity and paranasal sinuses, with a latency period typically between 30 and 40 years. This means that a joiner exposed in their twenties may not develop cancer until their sixties. The long latency period does not reduce the seriousness of the risk — it makes it worse, because the damage is done decades before the disease manifests. Softwood dust (pine, spruce, cedar, larch, Douglas fir and all other coniferous species) is a respiratory sensitiser. It can cause occupational asthma through an immunological sensitisation mechanism. Once a worker is sensitised to softwood dust, even very low subsequent exposures can trigger severe and potentially life-threatening asthma attacks. Sensitisation is permanent. The COSHH assessment must identify which timber species are in use and apply controls appropriate to each hazard category.
MDF (medium density fibreboard) and other engineered wood-based panel products are treated as hardwood for COSHH purposes because they contain a mix of wood species including hardwoods, and the binding resins (typically urea-formaldehyde) add an additional inhalation hazard. MDF generates exceptionally fine dust during cutting and routing, and the formaldehyde content means it has its own specific exposure considerations in addition to the wood dust WEL.
Construction sites present additional challenges compared with fixed-workshop environments. Carpentry and joinery work is frequently carried out in partially completed buildings, corridors, stairwells, and other spaces with limited ventilation. Cutting stations are often set up in ad hoc locations without fixed extraction. Multiple trades work in the same areas, meaning that wood dust generated by one operative exposes nearby workers from other trades who have no RPE and no awareness of the dust hazard. All of these factors must be addressed in the COSHH assessment.
2. Controls for Wood Dust
COSHH Regulation 7 requires that exposure to wood dust is prevented or, where prevention is not reasonably practicable, adequately controlled. The hierarchy of control must be applied in order. With the WEL now at 1 mg/m3, engineering controls — particularly local exhaust ventilation — are essential for virtually all powered woodworking activities on construction sites.
| Hierarchy level | Application to wood dust | Practical examples |
|---|---|---|
| Eliminate | Remove the need to cut, plane, route or sand timber on site | Specify pre-cut and pre-finished joinery components fabricated off-site in a controlled workshop environment with fixed LEV; use modular or pre-assembled units; design connections that do not require on-site modification |
| Substitute | Replace timber with materials that do not generate hazardous dust | Use aluminium, PVCu or composite framing instead of timber where the specification permits; specify factory-finished surfaces that do not require on-site sanding; use mechanical fixings instead of timber biscuits or dowels that require routing |
| Enclose | Contain the dust-generating process so that dust cannot escape into the work area | Enclosed cutting stations with integral extraction systems; dedicated dust-controlled cutting rooms with forced ventilation; enclosed sanding cabinets for small components |
| Local exhaust ventilation (LEV) | Capture dust at the point of generation before it disperses | On-tool extraction ports connected to an H-class vacuum for circular saws, mitre saws, routers, planers and sanders; dedicated extraction hoods for bench-mounted saws; H-class vacuum with floor nozzle for cleaning up. LEV systems must be examined and tested by a competent person at least every 14 months under COSHH Regulation 9 |
| RPE (respiratory protective equipment) | Protect the individual when engineering controls cannot reduce exposure below the WEL | Minimum FFP3 disposable mask (APF 20) for short-duration tasks with LEV also in place; powered air-purifying respirator (PAPR, APF 40) for extended tasks. RPE must be face-fit tested for each individual wearer. RPE is a last line of defence, not a substitute for LEV |
Housekeeping is a critical supplementary control. Wood dust settles on surfaces throughout the work area, and when disturbed — by foot traffic, sweeping with a dry broom, or air movement — it becomes re-entrained in the air and re-exposes workers. All wood dust deposits must be cleaned up using an H-class vacuum, never with a dry broom or compressed air. Compressed air cleaning is specifically prohibited by COSHH for any carcinogenic substance. Wet sweeping is acceptable as an alternative to vacuum cleaning on non-porous surfaces.
Health surveillance is a legal requirement under COSHH Regulation 11 for workers regularly exposed to hardwood dust, because hardwood dust causes an identifiable disease (nasal cancer and occupational asthma). Health surveillance should also be provided for workers regularly exposed to softwood dust because of the respiratory sensitisation risk. Health surveillance for wood dust exposure includes a respiratory questionnaire, lung function testing (spirometry), and where hardwood dust exposure is involved, examination of the nasal passages by an occupational health professional. The frequency of health surveillance reviews should be determined by the occupational health provider, but annually is typical.
3. Common Mistakes
Not updating the COSHH assessment for the 2020 WEL reduction
The wood dust WEL was reduced from 5 mg/m3 to 1 mg/m3 in January 2020. Any COSHH assessment that still references the old 5 mg/m3 limit is out of date and non-compliant. The five-fold reduction in the WEL means that activities and control measures that were previously adequate may no longer be sufficient. All wood dust COSHH assessments must be reviewed and updated to reflect the current WEL of 1 mg/m3, and controls must be validated against this lower limit.
Using an M-class vacuum instead of H-class for wood dust extraction
H-class vacuums have a filtration efficiency of 99.995% for particles down to 0.3 micrometres and are designed for hazardous dusts including carcinogenic wood dust. M-class vacuums have a filtration efficiency of 99.9% — which sounds similar but means they pass through 50 times more fine dust than an H-class unit. For hardwood dust (a Group 1 carcinogen) and for any wood dust at the 1 mg/m3 WEL, only H-class extraction is acceptable. Using an M-class vacuum provides a false sense of protection while re-emitting the fine respirable fraction into the worker’s breathing zone.
No health surveillance for workers exposed to hardwood dust
Health surveillance is a legal requirement under COSHH Regulation 11 for all workers regularly exposed to hardwood dust because it causes identifiable diseases — nasal adenocarcinoma and occupational asthma. The 30 to 40 year latency period for nasal cancer makes health surveillance especially important because the disease develops long after the exposure period. Baseline health surveillance (respiratory questionnaire, spirometry, nasal examination) must be carried out before first exposure, with periodic reviews thereafter. Failure to provide health surveillance is a specific COSHH compliance failure that the HSE actively looks for.
Not distinguishing between hardwood and softwood in the COSHH assessment
Hardwood and softwood present different health hazards and require different control considerations. Hardwood dust is a Group 1 carcinogen causing nasal cancer; softwood dust is a respiratory sensitiser causing occupational asthma. The COSHH assessment must identify which timber species are in use on the project, classify them as hardwood or softwood, and apply controls appropriate to each hazard. A generic ‘wood dust’ COSHH assessment that does not distinguish between hardwood and softwood fails to meet the ‘suitable and sufficient’ standard required by COSHH Regulation 6.
Sanding without local exhaust ventilation
Sanding — particularly orbital sanding and belt sanding — generates exceptionally fine wood dust that remains airborne for extended periods. The dust generated by sanding is predominantly in the respirable fraction, meaning it penetrates deep into the lungs. At the 1 mg/m3 WEL, sanding without on-tool extraction connected to an H-class vacuum will exceed the exposure limit within minutes. Every sander used on site must be connected to an H-class vacuum via the on-tool extraction port. Sanders without extraction ports should not be used on construction sites.
5. Frequently Asked Questions
Which wood species are classified as causing cancer?▾
All hardwood species are classified as Group 1 carcinogens by IARC for nasal and sinonasal cancer. This includes oak, beech, iroko, mahogany, teak, walnut, ash, elm, birch, cherry, maple and all other deciduous (broadleaf) species. The classification applies to the dust, not the solid timber. There is no safe hardwood species — the carcinogenic mechanism is linked to the dust characteristics of hardwoods generally, not to a specific chemical in individual species. Some species such as iroko and western red cedar also cause additional sensitisation reactions. Softwood species are not classified as carcinogens but are classified as respiratory sensitisers capable of causing occupational asthma.
What does the 1 mg/m3 WEL mean in practical terms?▾
The WEL of 1 mg/m3 is an 8-hour time-weighted average. In practical terms, it means that the average concentration of wood dust in the worker’s breathing zone over an 8-hour shift must not exceed 1 milligram per cubic metre of air. This is an extremely small amount — 1 mg is roughly the weight of a single grain of table salt dispersed in a cubic metre of air. For context, machine planing without extraction can generate concentrations of 5 to 20 mg/m3 at the operator’s breathing zone. Routing can generate 10 to 50 mg/m3. Even cross-cutting with a chop saw can generate 2 to 5 mg/m3. Without effective LEV, virtually all powered woodworking activities will exceed the WEL.
Is MDF covered by the wood dust COSHH assessment?▾
Yes. MDF and all other engineered wood-based panel products (chipboard, OSB, plywood, hardboard) are covered by the wood dust WEL of 1 mg/m3. MDF is treated as hardwood for COSHH purposes because it typically contains a mix of wood species including hardwoods, and the carcinogenic risk applies to the dust from these mixed species. Additionally, MDF contains urea-formaldehyde resin as a binder, and formaldehyde is itself a Group 1 carcinogen with its own WEL of 2 ppm (short-term, 15-minute). When MDF is cut or routed, both the wood dust WEL and the formaldehyde WEL apply. MDF generates exceptionally fine dust during cutting and routing, and on-tool H-class extraction is essential.
Does hand tool work require RPE for wood dust?▾
Hand tool work (hand sawing, chiselling, hand planing) generates significantly less dust than powered tools and is unlikely to exceed the 1 mg/m3 WEL during normal use. However, the COSHH assessment must still consider hand tool work, particularly where it is carried out for extended periods, in enclosed or poorly ventilated spaces, or with hardwood species. Where hand tool work is brief and carried out in well-ventilated conditions, RPE may not be required — but this conclusion must be justified in the COSHH assessment based on the specific circumstances. Where there is any doubt, air monitoring should be carried out to confirm that the WEL is not exceeded. Sweeping up wood dust shavings from hand tool work with a dry broom is not acceptable — H-class vacuum cleaning is still required.
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