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Calculation Machine

Cleanroom Air Changes Calculator

ACH and HEPA coverage by ISO class.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Air changes
60 ACH
Supply airflow
3,600 CFM
HEPA ceiling coverage
15-25%
Room volume
3,600 cu ft
2x2 ft HEPA modules at 500 CFM
8

Quick answer

Cleanroom air changes rise sharply with class, from about 20 ACH at ISO 8 to several hundred at ISO 5.

The formula

CFM = volume x ACH / 60

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Room area400 sq ft
  • Ceiling height9 ft
  • ISO classISO 7 (Class 10k)

Result

  • Air changes60 ACH
  • Supply airflow3,600 CFM
  • HEPA ceiling coverage15-25%
  • Room volume3,600 cu ft
  • 2x2 ft HEPA modules at 500 CFM8

How to use the Cleanroom Air Changes Calculator

  1. 1Enter room dimensions and target ISO class.
  2. 2Distribute HEPA modules evenly to hit the coverage percentage.
  3. 3Hold the room positive to adjacent lower-class spaces.

Frequently asked questions

Why does class drive airflow so hard?

Cleanliness depends on dilution and sweep — more air changes means particles are removed before they settle.

Unidirectional flow?

ISO 5 and cleaner usually need unidirectional 90 FPM airflow, not just high ACH.

About this calculator