Airflow physics on site is simple: you need enough moving air, in the right place, with minimal leaks and resistance. Get those right and capture is reliable.

Capture at source: velocity beats volume

• Position hoods or shrouds as close as practical to the dust generation point; a few centimetres matters more than a bigger fan.
• Keep openings small and targeted; large gaps dilute capture velocity.
• Use water suppression and slower cutting speeds to reduce dust generated, making capture easier.

Pressure, resistance and ducting

• Every bend, flex hose and rough surface adds pressure loss (Pa). Use the largest practical diameter and smooth, short runs.
• Avoid tight 90-degree bends; two 45s often flow better.
• Seal joints; small leaks destroy capture velocity even if the total flow number looks fine.

Air scrubbers and negative air

• Place air scrubbers to create a clean-to-dirty airflow path. Exhaust away from workers.
• For enclosures, aim for slight negative pressure so dust does not escape; ensure make-up air so the fan is not starved.
• Think air changes per hour as a guide, but judge success by visible capture and reduced airborne particulate on a meter.

Filter loading: the silent airflow killer

• As filters load, static pressure rises and flow drops. Stage filtration and change pre-filters early.
• Watch the unit’s gauge where fitted and confirm at the task: if dust escapes the hood, service now.

Measure, adjust, repeat

• Use simple indicators: smoke tubes, talc puffs, or a particulate monitor to verify direction and reduction.
• Move the hood closer, tighten seals, or simplify duct paths before reaching for a bigger fan.

Design for capture velocity, protect it with good ducting and seals, and preserve it by managing filter loading. That is the physics that matters on site.