Not all dust behaves the same. Particle size distribution (PSD) determines where dust deposits in the respiratory tract, how long it stays airborne, and which controls will actually work. Understanding PSD helps you design controls that are effective and proportionate.

What PSD tells you

PM10 covers particles likely to be inhaled; PM4 approximates the respirable fraction that reaches gas-exchange regions; PM2.5 and PM1 remain airborne longest and penetrate deepest. RCS risk sits mainly in the respirable range, while wood dust hazards often dominate in the inhalable fraction, though there is still a harmful fine component.

Choose controls that fit the size

Apply the three-layer framework. For capture at source, use tool-mounted extraction and water suppression to prevent both coarse and fine emissions. For capture in the air, deploy air scrubbers or negative air machines with H13/H14 HEPA where fine or carcinogenic dusts are present; size by required air changes and under-load airflow, not free-air figures. For surfaces, use H-class industrial vacuums with high-efficiency filtration; avoid sweeping and compressed air, which re-suspend fines.

Monitoring that informs action

Use monitors that report at least PM10, PM4 and PM2.5. A rise in PM1/PM2.5 suggests smoke or fume-like particles that need high-efficiency filtration and improved capture at source. A PM10-dominant profile points to cutting, sanding, or housekeeping issues. Trend size fractions through the shift so you can link peaks to tasks and adjust controls in real time.

From PSD to risk

Compare fraction-specific readings with relevant limits and guidance. For RCS, prioritise PM4 trends and confirm using periodic personal sampling under COSHH. Where fine fractions dominate, specify H14 filtration and check for leakage paths; where coarse fractions dominate, tighten housekeeping and material handling.

Practical takeaways

• Measure multiple size fractions; do not rely on a single “dust” number.
• Let PSD guide control choice: fine fractions need high-efficiency HEPA and tight containment.
• Trend PSD against tasks to pinpoint sources and verify fixes.
• Confirm respirable risks with personal sampling where required by COSHH.

A clear view of PSD turns generic dust control into targeted, effective risk reduction.