Mass vs number: Understanding air in your workplace

PM mass vs particle count: what you need to know

• PM values: Useful for regulatory comparison

• Particle count: Shows how many sub-micron particles are present in real time, revealing short-term fluctuations

Which channels matter

• 0.3 µm: Indicator of sub-micron particle activity

• 0.5 µm: Useful for tracking indoor trends

• 1.0 µm: Reliable for indoor trend data

Use case example 1: manufacturing environments

A factory with welding or cutting operations may have PM2.5 within compliance limits. However, particle counts reveal sub-micron dust spikes during certain shifts, allowing facilities managers to prioritise additional filtration or adjust processes to reduce exposure.

Use case example 2: London Underground

The London Underground is a complex environment with high passenger numbers, frequent train movements, and variable ventilation. While PM2.5 readings might suggest air quality is acceptable, particle counts can reveal spikes in sub-micron particles on platforms, in tunnels, and in ticket halls.

Air quality teams can use this data to:

• Identify persistent hotspots where ventilation or filtration improvements are most needed

• Monitor real-time changes during peak passenger periods or service disruptions

• Evaluate the effectiveness of interventions, such as new filters or air-cleaning technologies

By tracking both PM and particle numbers, transport operators can spot problem areas early, protect workers and passengers, and prioritise where high-precision equipment or filtration is needed.