An industrial dust detector is a fixed or portable instrument that quantifies airborne particulate concentration in mg/m³ or µg/m³ and outputs an analog or digital signal for trend logging, regulatory reporting, or broken-bag detection on a baghouse [S2][S6].
Four sensing families dominate 2026 spec sheets: optical (light-scatter, including laser backscatter), triboelectric (induced-charge probe), electrostatic/inductive, and microwave [S2]. Each maps to a different combination of particle size, dust loading, pipe geometry, and explosion-risk zone, which is why a single spec sheet rarely covers all duties on a plant.
Four Sensing Principles and What They Actually Measure
Light-scatter optical dust detectors (also called optical particle counters or laser backscatter monitors) drive a laser or LED into the sample stream and infer mass concentration from the intensity of scattered light, with laser-backscatter AGA-series units working at (650 ± 20) nm wavelength under 5 mW/m² power density and resolving particles ≥ 5 µm in both workshop and pipeline mounting [S4]. A typical static range band is 0-100/500/1000/4000 mg/m³, response time ≤ 10 s, and drift ≤ 2 % F.S., with IP66 ingress protection and 24 VDC at ≤ 2.5 W for field deployment [S4].
Triboelectric and electrostatic (inductive) probes insert into the duct or stack and measure the charge transferred when particles impact or pass the sensing rod, with industrial electrostatic units specified for continuous particulate-emission monitoring and 24 VDC operation across 15-32 V [S5][S7]. The probe principle is favoured on baghouse outlet ducts because it responds fast to a broken filter bag, and dedicated explosion-proof variants carry Ex marking for duct-side mounting [S6][S7].
Capacitive and microwave dust detectors round out the catalogue: capacitive sensors read changes in dielectric between electrodes as dust loading shifts, while microwave units transmit through the duct and read attenuation [S2]. High-range mass instruments for emission monitoring often quote 0.1-3000 mg/m³ with ±15 % relative error, covering the high end of cement, metal-smelter, and power-station duties [S8].
Measuring Range, Particle Size, and Resolution Bands
Range is the first number to lock in, because principle choice collapses once the upper limit is fixed. Ambient IAQ and cleanroom dust detectors typically read 0-6000 µg/m³ with ±10 % accuracy, splitting PM2.5 and PM10 mass channels for occupational-hygiene reporting [S3]. Stack and process monitors sit one to three decades higher, at 0-1000 mg/m³ or 0-4000 mg/m³ full scale, with laser-backscatter AGA-series models switchable across 0-100/500/1000/4000 mg/m³ bands so a single transmitter can be re ranged in the field [S4].
Particle size and channel count decide whether you need an optical particle counter (PM0.3/0.5/PM1.0/PM2.5/PM10 simultaneous channels) or a simple mass transmitter [S4]. Optical counters resolve size bins down to 0.3 µm, which matters for pharmaceutical isolators and semiconductor cleanrooms where sub-micron losses drive yield, while a baghouse outlet only needs bulk mass trend plus a high-trip alarm [S3][S4]. For higher-load mass duties above 1000 mg/m³, electrostatic and triboelectric probes remain the more linear choice because optical heads saturate and need shorter optical paths [S5][S7][S8].
Drift, response time, and warm-up are the second-tier numbers. AGA-series backscatter units are rated at drift ≤ 2 % F.S. and response ≤ 10 s, which is acceptable for trend and broken-bag detection but not for closed-loop control of a filter differential [S4]. If the application is control, add a dust particle meter reference channel or specify a faster triboelectric probe at the controller input.
Hazardous-Area Certification and Zone Assignment
Any dust detector mounted in a Zone 20, 21, or 22 area (continuous dust cloud, likely cloud during normal operation, or cloud unlikely in normal operation) needs Ex marking appropriate to combustible dust, not just gas groups; the AGA6050 carries dual gas and dust explosion-proof certification for hazardous-area mounting [S4]. General-purpose units (no Ex marking) are restricted to non-classified shells or to sample-conditioning cabinets located outside the classified boundary.
For duct and pipeline mounting, look for an explosion-proof enclosure on the head, ingress to IP66 or better, and a process-side rating that handles the duct vacuum or positive pressure; AGA-series IP66 plus online calibration without disassembly is the typical pattern on Chinese-OEM laser-backscatter units shipped in 2025-2026 [S4]. When the dust is also flammable (grain, flour, aluminium, sugar, toner, pharmaceutical powder), combine dust-Ex with gas-Ex dual marking to avoid having to swap the unit when the zoning review changes [S4][S7]. See the explosion-proof vs anti-static selection map for the rating language used in plant specifications.
For a broader read on fixed-gas detection in adjacent emissions-sampling systems (CO, NOx, SO2 alongside particulate), the multi-gas detector RFQ spec covers cross-sensitivity and probe-routing choices that affect the dust-channel location.
Comparison: Optical vs Triboelectric vs Electrostatic vs Microwave
Use this comparison as a quick shortlist gate before pulling data sheets. Read the four axes (range, particle size, Ex rating, typical application) as decision criteria, not as a ranking. [S4]
Optical (laser backscatter / LED scatter): range 0-100/500/1000/4000 mg/m³ on AGA-class units [S4], 0-6000 µg/m³ on IAQ PM2.5/PM10 monitors [S3]; resolves ≥ 0.3 µm size bins on full particle counters [S4]; dual gas+dust Ex optional [S4]; best for cleanroom, IAQ, low-to-mid stack concentrations, and baghouse outlet trend.
Triboelectric (inductive probe): range scales with probe length and electronics, typically 0.1-3000 mg/m³ with ±15 % error on industrial emission units [S8]; effective on particles ≥ 1 µm; intrinsically safe/Ex versions common; best for broken-bag detection on fabric filters and high-load ducts [S6][S7][S8].
Electrostatic (charge-induction): 0-1000 mg/m³ class on industrial emission monitors at 24 VDC / 15-32 V [S5]; good for sub-micron smoke and fumes; duct or pipeline insertion; Ex variants available; best for welding fume, metal-smelter offgas, and emission-compliance trend [S5][S7].
Microwave: lower market share; bulk-load reading through duct attenuation, suited to very high dust loadings where optical sensors saturate; used on coal, cement, and pneumatic conveying lines per general industrial-dust-detector guidance [S2]. Microwave is normally excluded when the dust is wet, sticky, or has a high dielectric loss, which is a frequent failure mode in real plants.
Who Optical/Tribolectric/Electrostatic Is For, and Who Should Not Pick the Mainstream Option
Pick optical (laser backscatter) when the application is cleanroom, IAQ, or low-concentration stack with PM2.5/PM10 reporting required; PM0.3 channel availability on AGA-class online units makes this the only realistic choice for pharmaceutical and semiconductor cleanrooms [S3][S4].
Pick triboelectric or electrostatic when the application is a baghouse outlet, an emission-compliance trend, or any high-load duct where optical sensors saturate; a 0.1-3000 mg/m³ electrostatic or triboelectric probe will outlast an optical head in cement, metal-smelter, or power-station service [S5][S7][S8].
Do not pick optical for wet, condensing, or sticky dust (oil mist, paint overspray, lime hydrate) because condensation on the optics drives false trips and drift beyond the rated ≤ 2 % F.S. [S4]. Do not pick triboelectric for cleanroom or IAQ because the lower detection limit is too high and the probe is too large for the duct. Do not pick any of the four for oxygen-deficient service without confirming the certification covers the gas group; if the duty is mixed gas and dust, spec a gas detector on the same loop and dual-marked dust detector at the head [S4].
For personal protection around the same dust hazard, remember that engineering controls (a fixed dust detector loop with alarms) sit above PPE in the hierarchy of controls; a correctly ranged dust transmitter is what makes the dust mask selection defensible in an audit, because the mask is matched to the measured PM2.5/PM10 profile, not assumed.
Output Protocols, Calibration, and Integration with Plant DCS
Most industrial dust detectors expose 4-20 mA analog, 0-10 V, RS-485 Modbus, or relay outputs; AGA-series laser backscatter units publish 4-20 mA, RS-485, and switch output, with the standard signal routed to PLC, DCS, or IPC [S4]. Compatibility with HART, PROFIBUS PA, or Foundation Fieldbus is vendor-specific and not in the AGA-class base spec, so verify the bus type against the DCS I/O list before purchase.
Online calibration without duct disassembly is now standard on 2025-2026 optical units and removes a recurring maintenance cost; the AGA series and most AGA-class Chinese-OEM units support in-situ zero/span check [S4]. Triboelectric and electrostatic probes are usually zeroed at commissioning and re-zeroed after each filter change, because the probe's baseline charge shifts with humidity and probe fouling [S6][S7].
Mounting distance is a separate spec line: AGA-class backscatter units are rated 0.7-5 m in open environment and 0.7-20 m in pipe, which sets the duct length the installer must provide between the sample point and any bend or damper [S4]. Outside that range, accuracy and noise rejection degrade and the unit must be moved, not re calibrated.
Limitations, Failure Modes, and What to Verify in the RFQ
Drift, condensation, and fouling are the three field-failure modes for optical dust detectors; condensation on the lens produces positive bias, dust build-up on the lens produces negative bias, and either will push the reading outside the rated ≤ 2 % F.S. drift without any process-side cause [S4]. The RFQ should call out purge-air availability on optical heads, automatic lens-blow-down on triboelectric probes, and a documented re-zero interval.
Range, accuracy, and response time trade off against each other; the same AGA-class unit can be set to 0-100 mg/m³ for IAQ or 0-4000 mg/m³ for stacks, but at the high end the ±10 % accuracy budget on PM2.5/PM10 IAQ units (e.g. the GAOTek NB-IoT 0-6000 µg/m³ SKU) does not transfer to a stack-monitor cert [S3][S4]. The RFQ must state the regulatory regime (e.g. US EPA PS-11, EU IED, China HJ/T 397) the unit will be used under, because the cert and the range band must match.
Finally, verify that the spec'd Ex marking matches the plant's area classification, not the marketing brochure; the AGA6050 dual gas+dust Ex is a different SKU from the general-purpose AGA6050, and the difference is in the certification documents, not the visible head [S4]. If the area classification is not yet final, hold the order until the hazardous-area drawing is approved, or specify a general-purpose unit with a documented upgrade path to Ex.
Track the next two signals before finalising vendor selection: the AGA-series datasheet revision from Aiyi/AIYI Technologies (laser-backscatter AGA6050 dual-Ex variant and PM0.3/PM1.0 channel options are the items to watch) [S4], and the GAOTek industrial emission detector (24 VDC electrostatic, 15-32 V operating range) catalog update for any move into dual Ex or bus-protocol expansion [S5]. These two will set the 2026-2027 price band for optical and electrostatic dust detectors respectively.