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Air Scrubber ACH Calculator (Air Changes Per Hour)

Calculate how many HEPA air scrubbers you need to hit a target air changes per hour (ACH) for mold remediation, dust control or air cleaning — and see the actual ACH your setup delivers.

How air changes per hour works

Air changes per hour (ACH) is how many times the full volume of air in a space is filtered each hour. The formula is: CFM needed = room volume (cu ft) × target ACH ÷ 60. Divide by your scrubber's CFM rating to get the number of units. Remediation specifications commonly require a minimum of 4 ACH, with 6 or more for active or high-contamination work.

This is a planning estimate. Filter loading, room shape, ceiling obstructions and air leakage all affect real-world performance — always follow your remediation protocol and, where applicable, third-party clearance requirements.

Want an exact quote?

These are planning estimates. Tell us your project details and we'll confirm the right equipment and pricing.