The Difference Between Self-purification Time and Recovery Time in The Clean Room

What are the differences between the self-purification time and the recovery time in the clean area?

I. Core Definition and Legal Basis

According to EU GMP Annex 1) and (reconfirmation requirements for clean rooms), the differences between the two are as follows:

Target	Clean-up Time	Recovery Time
Definition	The time required for the clean area to return to "static" particle limits by operating the HVAC system after the operation is completed.	The time it takes for the clean area to reach the specified clean level again after dynamic disturbance (such as door opening, material transfer)
Test scenario	Static → Static Recovery (such as cleaning up after production)	Dynamic → Dynamic recovery (such as control of particle diffusion after the opening of a pass box)
Regulatory requirements	It needs to be determined and recorded during the confirmation process, with the guideline value being ≤ 20 minutes	This needs to be verified through airflow visualization studies, usually requiring a duration of ≤ 5 minutes
Testing method	The particle counter continuously monitors until it reaches the ISO14644 static sta	Artificial simulation interference (such as smoke release tests), record the standard duration of particle concentration
Application Object	The entire cleanroom or key area (such as the filling line)	Local area (such as around the pass box, at the equipment openings)

II. Comparison of Test Standards and Scenarios

1. Requirements for Self-Cleaning Time Test

• Test Conditions:

· Initial State: Simulate the maximum pollution load (such as residual particles after cleaning)

· Acceptance Criteria: Reach the static particle limits as listed in Table 1 (such as A-class area ≥ 0.5μm particles ≤ 3,520/m³)

2. Recovery Time Test Requirements

• Test Conditions:

· Interference Simulation: Open the pass box for 30 seconds

· Acceptance Criteria: Particle concentration returns to the dynamic standard

III. Key Points for GMP Implementation

1. Variations in Verification Strategies

• Self-cleaning time: To be tested after the initial confirmation of the cleanroom and major changes

• Recovery time: To be tested during equipment / layout changes or annual reconfirmation

2. Test Frequency