When extraction underperforms, the layout is usually the culprit. Pressure losses multiply through long, tight, leaky, or crushed runs, and the result is weak capture at the point of use.

How layouts kill flow

• Excessive length: every metre adds friction and reduces under-load airflow.
• Sharp elbows and sudden reducers: turbulence robs energy and drops capture velocity.
• Undersized branches: choked lines increase static pressure and starve other pickups.
• Leaky joints: small gaps equal big cumulative losses.
• Corrugated or damaged hose: higher friction, dust build-up, and blockages.

Diagnose before you replace equipment

• Inspect the entire run end-to-end. Look for kinks, flattened sections, loose clamps, and dust piles near leaks.
• Measure at the hood with a simple anemometer. Compare before/after removing bends or opening blocked filters.
• Track airborne particulate with a PM meter in the breathing zone. If numbers fall when you straighten a run, you have your cause.

Rework for low resistance

• Shorten runs and relocate the unit closer to the source if practical.
• Swap tight elbows for large-radius bends and use gradual transitions when changing diameter.
• Seal every joint and support ducting to prevent sagging or crushing.
• Balance branches with dampers or adjust usage to avoid starving critical points.

Ducting systems are only as effective as their layout. Before upsizing machinery, re-route for smoother, shorter paths and confirm gains with simple measurements.

Practical takeaways

• Length, bends, leaks, and damage are the main airflow killers.
• Measure at the hood and in the breathing zone to guide fixes.
• Rework to gentle curves, sealed joints, and supported runs.
• Re-check after filter changes; under-load performance shifts as filters load.

A clean, efficient duct run often restores capture without new equipment and keeps controls within COSHH good practice.