Air changes per hour (ACH) is a simple way to size air scrubbers and set expectations for background dust control. Get the calculation right, use under-load airflow, and you will know whether your setup can clear the space in a reasonable time.

ACH in one line

ACH = airflow (m³/h) ÷ room volume (m³). Room volume is length × width × height. Use the scrubber’s airflow under load with filters and ducting attached, not the free-air figure.

Set a realistic target

For general construction dust control, 6 ACH is a practical baseline; for higher-risk tasks or leaky spaces, 10–12 ACH is more reliable. These are rules of thumb, not regulations, and they work best alongside on-tool capture and housekeeping.

Worked example

A room is 7 m × 4 m × 2.5 m = 70 m³. To achieve 10 ACH you need 700 m³/h under load. If your unit delivers 550 m³/h under load, you will get ~7.9 ACH; add a second unit, improve ducting, or reduce leaks to reach the target.

Make ACH meaningful

Place the intake near the source and direct clean discharge across the breathing zone. Avoid short-circuiting between outlet and intake. Keep prefilters clean to maintain the calculated ACH through the shift. If doors open frequently, allow extra capacity or add a second unit.

Verify with data

Use a particulate monitor to check how quickly the room clears after dusty tasks. If levels remain high, increase ACH, improve placement, or fix leaks. For high-hazard dusts, ensure the final filter stage is H14 and confirm seals are intact.

Practical takeaways

• Calculate ACH with under-load airflow and actual room volume.
• Target 6–12 ACH depending on risk and leakiness.
• Place units to sweep the breathing zone and avoid short-circuits.
• Keep prefilters clean and verify improvement with a PM meter.

ACH is a planning tool, not a guarantee. Combine it with the Dust Arrest three-layer approach—capture at source, control in the air, and clean surfaces—for reliable, repeatable results.