Measurement method
Optical particle counter
Part of: Low-cost sensors
Also: OPC, light-scattering photometer, nephelometer, particle counter
An instrument that draws air past a light beam and registers each particle by the light it scatters, converting the signal to a size and a count. It is the principle behind nearly every real-time particle measurement made indoors, from research instruments to consumer sensors.
What it is
Light scattering is what makes continuous particle measurement possible. A filter method weighs what it collects and gives one accurate number for a whole day; an optical counter gives a number every second, which is the only way to see a cooking peak, a candle, a vacuum cleaner or the effect of opening a window.
The trade is accuracy for time resolution, and the reasons are worth knowing. The instrument measures scattered light, not mass, and converts between them by assuming a density, a refractive index and a shape. Those assumptions hold for the aerosol the instrument was calibrated against and not for others, so the same device reads differently in a kitchen, in wildfire smoke and beside a road. Small particles scatter too little light to be counted at all, which is why an optical instrument underestimates ultrafine particles, and high humidity swells particles and inflates the reading.
Co-location against a reference method is what makes its numbers comparable.
What the studies report
| Linked to | Effect | Population | Study design | Source | Checked |
|---|---|---|---|---|---|
| Particulate matter (PM₂.₅ and PM₁₀) | ratio 46.9 | — · laboratory | laboratory measurement-method comparison: cooking fumes generated under simulated typical cooking conditions, manual gravimetric analysis as benchmark against an optical particle counter (Promo 3000), a photometer (DustTrak 8533) and infrared spectrophotometry | F-0109 Wang et al. Cooking Fume Particulate Matter as an Indoor Air Pollution S… (2026) | machine |
| Particulate matter (PM₂.₅ and PM₁₀) | ratio 2.13 | — · laboratory | laboratory measurement-method comparison: cooking fumes generated under simulated typical cooking conditions, manual gravimetric analysis as benchmark against an optical particle counter (Promo 3000), a photometer (DustTrak 8533) and infrared spectrophotometry | F-0110 Wang et al. Cooking Fume Particulate Matter as an Indoor Air Pollution S… (2026) | machine |
Each row is one Finding — a sentence as printed in one study, recorded with its page in the Coridum Knowledge Base. Follow the Finding number for the exact wording and the citation. Checked says who verified the row: machine means every automatic check passed and the surrounding text was read; person means someone read the sentence in the document. Rows are re-checked by a person over time. The studies are curated in the Coridum Knowledge Base; the reading of them together is a Claim, shown separately.
Cite this page
Coridum Research. Optical particle counter. Coridum Knowledge G-0174, 16 September 2026. https://coridum.com/k/G-0174/