Filters load, resistance rises, and airflow drops. That is when capture fails, not when you first switch on. Maintaining performance under filter resistance is the difference between compliant dust control and invisible exposure.

Focus on under-load, not free-air

Manufacturers quote free-air figures, but what matters is airflow under load through hose, tool, and filters. Track differential pressure (Pa) across filters; rising pressure with falling airflow signals clogging or leaks. For respirable risks such as silica or welding fume, ensure final filtration is HEPA to H13 or H14, and that the whole machine is sealed so bypass cannot occur.

Practical ways to keep airflow stable

• Stage your filtration. Use prefilters or fleece bags to catch coarse dust and protect fine filters from rapid loading.
• Change by condition, not calendar. Set differential pressure triggers for prefilter and main filter changes. Record Pa at install and agree a change-out threshold.
• Use automatic filter cleaning when generating fines. Pulse or vibration systems slow resistance build-up; pause extraction briefly to allow effective cleaning.
• Shorten and widen the air path. Keep hoses as short as practical, minimise tight bends, and match the correct diameter to the tool port to reduce friction losses.
• Seal the system. Check gaskets, latches, and tool cuffs. Any bypass defeats even an H14 filter.
• Control the source. Slower cutting speeds, shrouds, and correct LEV hoods reduce the volume of airborne particulate you ask the filter to handle.
• Right-size air scrubbers and negative air units. Calculate required air changes and verify with a particulate monitor rather than relying on spec-sheet m³/h.
• Empty safely. Overfilled bags increase resistance and burst risk; replace before packed solid and de-dust the housing with an H-class vacuum.

Troubleshooting on site

• Visible dust plume escaping a tool shroud usually means inadequate capture velocity or a leak. Reduce hose length, inspect seals, and clean/replace prefilters.
• Motor pitch rising and falling suggests filter pulsing without recovery. Stop, clean, and swap a blocked prefilter.
• High Pa but normal airflow indicates blockage downstream (kinked hose). Low Pa and low airflow points to upstream restriction or a major leak.
• Keep a simple log: date, task, Pa, airflow/face velocity, filter changes. Trends prevent surprise failures.

Practical takeaways

• Measure differential pressure and airflow under load; don’t rely on free-air numbers.
• Protect fine filters with staged filtration and condition-based changes.
• Tighten the system: short hoses, good seals, correct cuffs.
• Combine source capture with room control and H-class housekeeping under COSHH.

Good dust control is a system, not a spec sheet. Verify performance with measurements, maintain filters proactively, and design the air path so resistance does not rob you of capture when the work gets dusty.