Respirable Dust Monitoring
Higgins-Dewell or GK 2.69 cyclone sampling per MDHS 14/4 for the 4 mg/m³ 8-hr TWA general respirable WEL, with optional XRD for respirable crystalline silica. UKAS-accredited analysis at IOM.
The fine fraction that reaches the alveoli
Respirable dust is the fraction fine enough (50% cut at 4 micrometres aerodynamic diameter, BS EN 481) to bypass the upper airways and reach the alveolar region of the lung. It includes essentially all the truly hazardous fine particles in stone-cutting, concrete-grinding, ceramic processing and cement handling — including the respirable crystalline silica that causes silicosis and lung cancer.
The general respirable WEL is 4 mg/m³ as an 8-hour TWA. Where the dust contains crystalline silica, the substance-specific WEL of 0.1 mg/m³ (respirable, 8-hr TWA) takes over — and that 0.1 mg/m³ limit is one of the most commonly exceeded WELs in the UK.
We sample respirable dust with a Higgins-Dewell or GK 2.69 cyclone at the calibrated flow rate (typically 2.2 L/min), with a pre-weighed 25 mm filter. The filter can be analysed gravimetrically for the general WEL or directly by XRD for crystalline silica content.
Where respirable monitoring matters most
These are the workplaces where the respirable fraction dominates the health risk.
Stonemasonry & Memorial Masons
Cutting, dressing and engraving of natural stone. Even wet-cutting operations can give respirable silica exposures above the 0.1 mg/m³ WEL once the slurry dries on benches and tools.
Engineered Quartz Worktops
Fabrication of engineered-quartz kitchen worktops has emerged as the highest-silica industry in the UK, with multiple confirmed cases of accelerated silicosis in fabricators under 40.
Concrete Cutting & Drilling
On-site concrete cutting, coring, scabbling and grinding. The first-hour exposure on dry cutting routinely exceeds the WEL by an order of magnitude.
Brick & Block Manufacture
Press, kiln return, sawing and grinding operations in brick and concrete-block plants.
Ceramics & Pottery
Body preparation, glaze spraying, fettling and kiln-fired product handling. A historic Staffordshire industry where the HSE has done extensive proactive inspection.
Quarrying & Aggregate Processing
Drilling, crushing and screening operations. Cab pressurisation, water suppression and enclosed control rooms are the standard controls.
How we sample respirable dust
Cyclone sampling per MDHS 14/4 with optional XRD for crystalline silica per MDHS 101.
Frequently Asked Questions
What is the general respirable dust WEL?
The general respirable dust WEL in HSE document EH40 is 4 mg/m³ as an 8-hour time-weighted average. It applies to the respirable fraction (50% cut at 4 µm aerodynamic diameter) sampled with a calibrated cyclone per MDHS 14/4.
How is respirable dust different from inhalable dust?
Inhalable dust includes everything a worker can breathe in (up to ~100 µm), sampled with an IOM head. Respirable dust is only the very fine fraction (50% cut at 4 µm) that reaches the deep lung, sampled with a cyclone. Different sampling heads, different WELs, different analyses.
When does respirable crystalline silica become the relevant limit?
Where the respirable dust contains more than about 1% crystalline silica by mass, the substance-specific WEL of 0.1 mg/m³ takes precedence over the general 4 mg/m³ respirable WEL. In stone, concrete and quartz-worktop industries this is essentially always the case.
Can the same sample be tested for both general respirable and silica?
Yes. A respirable filter analysed gravimetrically for total respirable mass can usually be re-analysed by XRD for crystalline silica content, giving both results from a single sample.
How much does respirable dust monitoring cost?
A typical baseline respirable survey of 4 to 6 workers, including report, starts from around £900 to £1,200 plus VAT. UKAS-accredited gravimetric analysis adds approximately £40 per sample; adding XRD silica analysis is approximately £85 per sample.