General Inhalable Dust Monitoring
IOM-head sampling per MDHS 14/4 for the 10 mg/m³ 8-hr TWA general inhalable WEL. UKAS-accredited gravimetric analysis at a UKAS-accredited laboratory.
The 10 mg/m³ baseline that catches everything else
Where a workplace generates dust that doesn't have a specific Workplace Exposure Limit of its own — mixed manufacturing dust, paper dust, plastic dust, mineral fines below the silica threshold, food processing dusts not separately listed in EH40 — the relevant benchmark is the general inhalable WEL of 10 mg/m³ as an 8-hour time-weighted average.
This is sampled with the IOM head per MDHS 14/4 in exactly the same way as wood dust, flour dust and grain dust. The advantage of using the IOM head as a default is that the inhalable filter can usually be analysed for multiple analytes (gravimetric mass plus, for example, ICP-MS for metals) without re-running the survey.
Where the gravimetric result is close to the 10 mg/m³ limit, we recommend dust speciation — XRD for crystalline silica content, ICP for metal content, EDX for inorganic composition — to confirm that no substance-specific WEL has been exceeded.
Where the general inhalable WEL applies
These are the workplaces where the 10 mg/m³ general WEL is the primary benchmark.
Recycling & Waste Transfer
Mixed waste sorting, RDF/SRF production, picking lines. Composition varies hourly — the general inhalable WEL is usually the right starting point.
Plastics & Polymer Processors
Compounding, regrind, masterbatch handling. Most polymers don't have a specific WEL but workers can be exposed to 10+ mg/m³ in poorly extracted compounding rooms.
Paper Converters & Printers
Sheet-fed paper dust during cutting and converting. Soft paper dust has no specific WEL — the 10 mg/m³ general inhalable applies.
Mineral & Aggregate Processing
Where silica content is below the 1% threshold for separate RCS assessment, the general inhalable WEL remains the benchmark for the bulk dust.
Mixed Manufacturing Workshops
Engineering shops with multiple processes — cutting, grinding, finishing — where the dust mix is too varied for single-substance assessment.
Construction Site Mixed Dust
General site dust on construction projects that contains multiple materials. The 10 mg/m³ general WEL applies alongside any substance-specific limits.
How we sample general inhalable dust
Standard MDHS 14/4 with the IOM head, with the option to add speciation analysis after the gravimetric finish.
Frequently Asked Questions
What is the general inhalable dust WEL?
The general inhalable dust WEL in HSE document EH40 is 10 mg/m³ as an 8-hour time-weighted average, applied to any dust that does not have a substance-specific limit. It is sampled using the IOM head per MDHS 14/4.
When does the general inhalable WEL apply?
It applies whenever a dust does not have its own WEL in EH40. If a more restrictive substance-specific WEL applies to any constituent (e.g. hardwood at 3 mg/m³, silica at 0.1 mg/m³), that one takes precedence.
Can the same sample be analysed for multiple substances?
Yes. An IOM filter sampled gravimetrically can usually be re-analysed by XRD for silica content or ICP-MS for metals afterward, so a single survey can cover several regulated substances cost-effectively.
How often should we monitor mixed inhalable dust?
Baseline survey on first occupation or major process change, then annually if results are well below the WEL, six-monthly if close to it, and within three months of any significant change to extraction or process layout.
How much does general inhalable dust monitoring cost?
A typical baseline survey of 4 to 8 workers in a single facility, with UKAS-accredited gravimetric analysis, starts from around £800 to £1,200 plus VAT.