20.08.2026
Gravimetric sampling cannot always confirm whether a workplace is dust compliant. Where the mass collected on the filter falls below the laboratory's limit of quantification (LoQ), the report states only that the concentration lies somewhere beneath that threshold. If the threshold happens to sit above the applicable exposure limit, the measurement can neither confirm compliance nor rule it out. As limits for different materials continue to fall, respirable crystalline silica among them, that situation is becoming more common rather than less.
Dustlight gives you a dust concentration in either case. Once the device is calibrated to your individual use case, it automatically reports the concentration each worker is exposed to over the course of a shift. In the Dustlight app you can review this data at any time and see who was exposed, when, and to what concentration, together with an immediate overview of compliance against the limit values applicable in your country.
The limit of quantification, and why compliance can be unknown
Two thresholds govern what a laboratory can report. The limit of detection (LoD) establishes whether a substance is present at all. The limit of quantification is the lower point at which a numerical concentration can be stated with acceptable confidence. It is the one that decides whether a compliance assessment is possible at all.
LoQ is set in mass per filter, typically a fraction of a microgram. Converting it into a concentration in µg/m³ means dividing by the volume of air drawn through the filter. Sampling flow rate is fixed by the method, so the only remaining variable is time: a shorter sampling run raises the detection limit and the LoQ expressed as a concentration, and a task lasting twenty minutes carries a far higher quantification threshold than a full shift.
The professional standard is explicit about where that threshold should sit. BOHS-NVvA guidance recommends choosing the analytical method and the sampled volume so that the LoQ stays below one tenth of the OEL (Testing Compliance with Occupational Exposure Limits for Airborne Substances, BOHS-NVvA). Against the ACGIH threshold limit value of 0.025 mg/m³ for respirable crystalline silica, that target is 2.5 µg/m³ of air.
Meanwhile the limits themselves are tightening, and they already differ by a factor of four between jurisdictions. Respirable crystalline silica, as an example:
| Jurisdiction | Applicable value, 8-hour TWA |
| EU limit value, Directive 2017/2398 | 0.1 mg/m³ |
| United Kingdom | 0.1 mg/m³ |
| Australia | 0.05 mg/m³ |
| Germany | 0.05 mg/m³ |
| OSHA, U.S.A. | 0.05 mg/m³, with a 0.025 mg/m³ action level |
| ACGIH Threshold Limit Value (TLV) | 0.025 mg/m³ |
Optical measurement and the calibration factor
Dustlight produces a concentration continuously, and its lower reporting threshold does not depend on accumulating weighable mass. A shorter observation period therefore does not raise it in the way a shorter sampling run raises a gravimetric LoQ. A figure is available whether the concentration is high or low.
The mechanism rests on a calibration factor, which Dustlight supplies as a material configuration. Light scattered by airborne particles gives their number and size. Converting that response into a mass concentration requires the density and optical behavior of the material, and a configuration holds those values for a specific dust. Selecting the silica configuration applies the factor derived for silica-containing dust, and the device then reports a concentration in µg/m³ that can be held against the applicable limit.
An optical result with a matched configuration is an estimate, not a laboratory determination of gravimetric sampling accuracy. Three boundaries define it.
The configuration assumes the named material dominates
Limit values in the silica configuration are set to 100 percent silica content. Few workplaces present a single substance, so a reading interpreted as silica may include a substantial fraction of other material.
No material is identified
Particles are counted and sized, not analyzed. Aerosols and liquid droplets in the same size range are registered alongside dust. The material is supplied by the user; it is never determined by the device.
Gravimetric sampling remains the reference method
Gravimetric sampling remains the reference method for formal exposure assessment and for legally binding compliance evidence, under EN 482 and EN 689 in Europe and the equivalent frameworks elsewhere.
From September 2026 the estimate narrows. Where the share of one specific substance in the dust is known, that percentage can be entered in the Dustlight app, and the reported concentration then describes that substance rather than total dust. This is the same distinction stated differently: the device does not detect materials, it measures particles and reports them against the composition the workplace has established.
The practical difference from a censored gravimetric result is straightforward. Dustlight states a concentration and whether it sits above or below the limit. A result below LoQ states only that the concentration is beneath a threshold which may itself exceed the limit.
General dust or a material configuration
Every device ships with the standard General Dust setting, which is the right choice more often than its name suggests and requires no knowledge of the material in advance. It was calibrated against a representative mixture at roughly 2.7 g/cm³, largely crystalline silica-containing dust with other materials included, and validated against gravimetric and laboratory-grade optical references.
When General Dust is enough
- Verifying an engineering control. Measuring the same task with local exhaust ventilation running and then switched off gives a percentage reduction that holds regardless of which configuration was selected. A single gravimetric filter covering a whole shift cannot isolate the effect of one intervention.
- Locating a source. Walking an area against the live measurement trace shows where concentrations rise.
- Attributing exposure to a task. TTime resolution frequently reveals that one step lasting five minutes accounts for a disproportionate share of a shift's dose — and therefore where a control will have most effect.
When a material configuration earns its place
- Warning thresholds are meant to trigger at the correct concentration.
- Direct comparison is intended, against a gravimetric sample or against an exposure limit.
- A single material or aerosol determines the process, particularly where its density or optical behavior differs substantially from the standard mixture.
Custom material configuration
With the update coming in September 2026, Dustlight adapts even more closely to your individual use case. Where you work with a material for which no configuration yet exists, a calibration factor can be derived from a gravimetric sample taken on site.
Recommended approach
Start broad. General Dust shows which areas carry the highest concentrations, how those concentrations behave across a shift, and how conditions differ between seasons. A joinery running hardwood panels will read differently during manual edge sanding than during machine ripping, and differently again with the extraction doors open.
Then sample where it matters. Gravimetric sampling is directed at those locations rather than distributed across the site: where concentrations appear highest, where the material is toxic or carcinogenic, or where compliance looks doubtful. Because each campaign is expensive, targeting it is what makes the budget go further.
Run both together. A device is worn beside the sampler so that both receive the same dust under the same conditions. The laboratory result is entered against the device average, which the software already holds, and the resulting configuration is named and stored.
Add the constituent share where composition is known. The September 2026 update makes the reported figure more accurate still. Where the composition of the dust is known, the share of the substance that matters can simply be entered in the app: a laboratory analysis reporting 20 percent quartz or 5 percent chromium is set as a percentage, and the calculation runs automatically. Dustlight then reports the concentration of that substance each worker is exposed to, and raises warnings against its limit rather than against the limit for the mixture. This is precisely why Dustlight does not detect materials. It measures particles and reports the result against the composition of your own workplace, which brings the reported figure as close as possible to the real concentration to which the worker is exposed. Where no analysis is available, the share can be set directly using the reference bands in the app for common materials such as concrete, granite and fibre cement.
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It means the mass collected was too small for the laboratory to state a concentration with acceptable confidence. The true value lies somewhere below that threshold. Where the threshold sits above the applicable exposure limit, the result can neither confirm nor rule out compliance.
Limits are low and falling, from 0.1 mg/m³ as the EU binding limit down to 0.025 mg/m³ as the ACGIH threshold limit value. BOHS-NVvA guidance recommends an LoQ below one tenth of the limit, which at the ACGIH value means 2.5 µg/m³. Meeting that at a fixed flow rate requires a long sampling period, which is why short-duration task sampling is the hardest case.
No. Gravimetric sampling with laboratory analysis remains the recognized reference method for formal exposure assessment and for legally binding compliance evidence. Dustlight supplies the time resolution, the task attribution and the numerical value in situations where a gravimetric result would be censored.