Secondary exposure is the harm caused when dust moves away from the task and exposes others, or when it is carried off site on clothing, skin, tools or vehicles. On UK sites this most often means respirable crystalline silica (RCS) and wood dust reaching offices, welfare areas, neighbours, or workers not directly involved in cutting or grinding. It matters because people receiving secondary exposure have not chosen to wear RPE, yet the health risk is the same; the HSE WEL for RCS is 0.1 mg/m³.

Where it happens

Typical routes include boots tracking dust into cabins, demolition debris drying and becoming airborne again, tool cases shedding dust in vans, and vacuum exhausts recirculating fine particles. Poor housekeeping and sweeping with brooms turn settled dust into airborne particulate.

Practical controls that work

1) Capture at source

• Fit on-tool extraction and water suppression to saws, grinders and breakers.
• Match the tool to a suitable industrial vacuum with M-Class or H-Class filtration; choose H14 where fine or carcinogenic dust is present.
• Plan tasks to cut outdoors or in screened areas to reduce spread.

2) Capture in the air

• Use air scrubbers or negative air machines to keep dust moving towards filters, not people. Size by airflow under load and position to create flow from dirty to clean zones.
• Close doors and create simple partitions to contain plumes.

3) Capture on surfaces

• Stop sweeping and compressed air. Vacuum floors, ledges and tools with high-efficiency filtration.
• Bag waste at source and damp down before moving.
• Adopt colour-coded mats at entry points and clean them frequently.

Decontamination and behaviour

• Issue site-only workwear; launder professionally. Never take dusty PPE home.
• Provide blow-through-free cleaning: use vacuums for clothing and tools; avoid airline guns.
• Keep vehicle cabs clean with a compact H-Class vacuum and change cab filters as scheduled.

Assurance

• Use a particulate monitor to spot-check PM2.5/PM10 levels in welfare and perimeter areas.
• Record control checks alongside COSHH assessments and update when processes change.

Practical takeaways

• Treat offices, welfare and vehicles as clean zones with enforced transitions.
• Replace sweeping with vacuuming and damp methods.
• Control dust at the task, then support with air cleaning and disciplined housekeeping.
• Use H14 where respirable or carcinogenic dusts are present.

Secondary exposure is preventable. A simple plan that combines source control, air management and disciplined housekeeping will protect those beyond the task and keep you aligned with HSE expectations.