Recovery Tests (Cleanroom Recovery Time Testing)
Recovery testing measures how quickly a cleanroom returns to its required cleanliness level after a temporary contamination event (e.g., personnel entry, equipment movement, door opening). This test is critical for cleanrooms, pharmaceutical facilities, hospitals, and semiconductor manufacturing to ensure air filtration efficiency and contamination control.

1. Purpose of Recovery Testing
Verifies HVAC & HEPA filter efficiency in removing airborne contaminants.
Ensures compliance with ISO 14644-3, EU GMP, and FDA cGMP guidelines.
Confirms air exchange rate effectiveness in cleanroom design.
Optimizes airflow patterns for contamination control.

2. Recovery Time Definition
Recovery time is the time required for airborne particle levels to return to an acceptable cleanroom classification after an artificial contamination event.
Measured as the time needed to restore particle concentration to:
100 times cleaner than the initial contamination level (ISO 14644-3 standard).
Original cleanroom classification levels (e.g., ISO 5, ISO 7).

3. Recovery Test Procedure
a. Equipment Required
Laser Particle Counter (LPC) – Measures airborne particle concentration.
Controlled Contamination Source (e.g., smoke, aerosol challenge).
HEPA-filtered cleanroom environment.
b. Test Steps
Baseline Measurement
Record the initial cleanroom particle count in normal conditions.
Introduce Contamination Event
Create a controlled contamination (e.g., using smoke, aerosol, or opening doors).
Allow particle levels to rise 10 to 100 times above the baseline.
Start Recovery Time Measurement
Monitor and record airborne particle reduction at set time intervals.
Determine Recovery Time
Recovery time is the moment particle levels return to the original cleanroom classification (e.g., ISO 5, 7, or 8).

4. Pass/Fail Criteria for Recovery Time
Cleanroom Class
Recommended Recovery Time (Minutes)
ISO 5 (EU GMP Grade A)
< 20 minutes
ISO 7 (EU GMP Grade B)
< 30 minutes
ISO 8 (EU GMP Grade C/D)
< 40 minutes
Pass: Cleanroom returns to classification within acceptable time.
Fail: Recovery takes too long → Requires HVAC or filtration adjustments.

5. Factors Affecting Recovery Time
Air change rate (ACH): More air exchanges = faster recovery.
HEPA filter performance: Inefficient filters slow down recovery.
Room design & airflow patterns: Poor airflow increases particle retention.
Personnel movement & door openings: More disruptions = longer recovery time.

6. Corrective Actions for Long Recovery Times
Increase air change rate (ACH).
Inspect HEPA filters for leaks or blockages.
Improve airflow patterns (adjust supply/exhaust placement).
Limit personnel movement & door openings.

7. Applications of Recovery Tests
Pharmaceutical Cleanrooms (EU GMP, FDA cGMP compliance).
Hospital Operating Rooms & Isolation Rooms (Infection control).
Semiconductor & Aerospace (Particle-sensitive environments).
Would you like a step-by-step test procedure or a calculation example for recovery time?