AHU / CLEANROOM REQUALIFICATION
Reference: ISO 14644-3:2019 + ISO 14644-2:2015
Objective: To verify that the AHU/cleanroom continues to maintain the required air cleanliness and environmental conditions during operation. ISO 14644-3 provides the applicable cleanroom test methods, while ISO 14644-2 establishes the monitoring/periodic-testing framework.
KEY REQUALIFICATION TESTS
- Airflow Volume / Velocity
→ Verify supply airflow and required air changes/velocity. - Room Pressure Differential
→ Verify pressure cascade between classified areas. - Airflow Direction / Visualization
→ Confirm airflow moves in the intended direction. - HEPA Filter Integrity / Leakage Test
→ Verify filter installation and absence of bypass/leakage. - Non-viable Particle Count / Cleanroom Classification
→ Verify compliance with designated ISO cleanliness class. - Recovery Test
→ Demonstrate the room’s ability to return to the specified cleanliness level after a particle challenge. Note: ISO 14644-3 does not recommend recovery testing for unidirectional airflow. - Temperature
→ Verify temperature remains within specified limits. - Relative Humidity
→ Verify RH/dew point remains within specified limits.
These tests are among the supporting/performance tests described by ISO 14644-3.
FREQUENCY — IMPORTANT INTERVIEW POINT
ISO 14644-3 itself does NOT prescribe one universal frequency for every AHU test. Periodic testing should be established through a documented, risk-based testing plan, considering monitoring results, facility design, and applicable regulatory/site requirements.
For ISO 14644-2, the specified maximum intervals include:
- Particle concentration classification:
≤ ISO Class 5 → 6 months
> ISO Class 5 → 12 months - Airflow volume/velocity → 12 months
- Room pressure differential → 12 months
REQUALIFICATION ALSO REQUIRED AFTER:
Major AHU modification / HVAC modification → Filter replacement → Significant maintenance → Failure/deviation → Change affecting airflow or pressure → Extended shutdown → Other risk-assessed events.
IN ONE LINE :
“AHU/cleanroom requalification is performed to demonstrate continued HVAC and cleanroom performance. Key tests include airflow, pressure differential, airflow visualization, HEPA filter integrity, particle classification, recovery where applicable, temperature, and RH. The periodic frequency should be established through a documented risk-based plan; ISO 14644-2 specifies 12-month maximum intervals for airflow and pressure-differential tests and 6/12 months for particle classification depending on ISO class.”