Optical dust sensors measure how particles scatter a laser beam. Larger particles scatter more light (especially forward), while very fine particles (PM1) scatter weakly. The detector converts the scattered signal into size bins and counts, which firmware estimates as mass. This simple physics underpins most site dust meters.

Why readings vary by dust type

• Refractive index: darker or more absorbing particles scatter less light, biasing mass low.
• Shape and roughness: fibres and flakes scatter differently to spheres.
• Humidity: water on particles increases size and scattering; readings can spike in damp air.

Practical steps for better data

• Placement: avoid direct spray, fog, and duct outlets; position at breathing height.
• Stabilise environment: where feasible, use gentle drying inlets or measure away from misting.
• Zero and check: use a zero filter cap or clean zone to confirm baseline before critical tasks.
• Validate: compare against a gravimetric sample for the dust you care about (e.g., silica vs wood dust).

Interpreting bins and PM values

• Bins show size distribution: a spike in coarse counts often points to sweeping or debris disturbance.
• PM1 and PM2.5 are better for respirable risks; use H13/H14 filtration on scrubbers when these rise.
• Watch trends: a falling PM with steady work usually means controls are effective; plateaus suggest filter loading or bypass leaks.

Link to controls

Use scattering-based readings to tune the three layers of control. If PM1 stays high despite source capture, reposition LEV hoods or increase air changes. If coarse counts jump during clean-down, switch to industrial vacuuming and stop dry sweeping. Always verify airflow under load and service filters before performance drops.