How to Use the Cleanroom Air Changes Calculator
Air Changes per Hour (ACH) measures how many times a room's entire air volume is replaced in one hour, and it's a common design metric for cleanrooms, operating rooms, and electronics manufacturing spaces where cleanliness matters. The formula is simple: multiply room width, length, and height to get volume (ft³), then divide hourly supply airflow (CFM × 60) by that volume.
Under the international ISO 14644 cleanroom classification, commonly cited industry reference ranges are roughly 240-600 ACH for ISO 5 (former Class 100), 60-90 ACH for ISO 7 (former Class 10,000), and 20-40 ACH for ISO 8 (former Class 100,000). These are general reference ranges only — the exact ACH required depends on the materials handled, the process, and your specific design criteria.
ACH is just one of several factors that determine cleanroom performance. Filter grade (HEPA/ULPA), airflow pattern (laminar vs. turbulent), room finish material outgassing, and particle generation from personnel and equipment all play a role, so ACH alone cannot guarantee a cleanliness class. Actual class certification requires certified particle count measurement and review by a qualified cleanroom engineer.
Frequently Asked Questions
Common industry reference ranges under ISO 14644 are roughly 240-600 ACH for ISO 5 (former Class 100), 60-90 ACH for ISO 7 (former Class 10,000), and 20-40 ACH for ISO 8 (former Class 100,000). Actual requirements vary by process and design criteria.
No. ACH is just one factor in cleanliness — filter grade (HEPA/ULPA), airflow pattern, room finish materials, and particle generation from people and equipment all matter too. Actual class certification requires certified particle counting and expert review.