Both real-time and gravimetric methods have a place on UK sites. Real-time monitors show trends second-by-second, helping crews adjust controls. Gravimetric sampling captures dust on a filter for laboratory weighing and is preferred for formal exposure assessment under COSHH.

What real-time is best for

• Task control: confirms water suppression, LEV, or air scrubbers are effective.
• Alarmed response: set action levels to pause work before exceedances.
• Optimising layouts: move ducting or scrubbers until PM drops where people work.

What gravimetric is best for

• Compliance-grade exposure data: time-weighted averages (e.g., RCS vs 0.1 mg/m³) by personal sampling.
• Calibration anchor: corrects optical bias for your specific dust mix.
• Dispute resolution: defensible records for clients and inspectors.

Combining both in practice

• Start with a gravimetric baseline for key tasks. Use those results to adjust the optical monitor’s factors if the instrument allows, or to interpret its trends correctly.
• Run real-time monitors daily to manage controls; schedule periodic gravimetric checks to verify assumptions and detect drift.
• Use personal sampling for high-risk roles; use area real-time monitors to protect everyone else on the floor.

Sampling tips that improve decisions

• Place real-time units at breathing height, away from direct jets; log pre-task, during, and post-task periods.
• Ensure gravimetric flow rates and media match the target fraction (inhalable vs respirable). Record task details and PPE.
• Report both data types together: “controls applied, PM fell by 70%, gravimetric TWA within WEL.”

Use the three-layer control framework with monitoring as the feedback loop: fix source capture first, then verify background air control and housekeeping. Real-time keeps the site safe from moment to moment; gravimetric keeps your evidence strong.