What parameters need to be tested for high-efficiency air supply outlets during cleanroom acceptance?
Acceptance testing for high-efficiency air supply outlets covers four main categories: visual inspection, airtightness, filter performance, and operational conditions:
I. Visual Inspection and Installation Acceptance (Visual and Dimensional Checks)
Housing: No deformation, rust, or dents on the casing; anti-corrosion coating intact; sealant at welds or joints is full and continuous, with no gaps or air bubbles; access panel is securely fastened.
Filter Appearance: Filter media free of damage, creases, or cracks; sealing gasket is flat, with no detachment or aging; bond between filter media and frame is tight.
Diffuser Plate: Installed flat and level; clips are secure; perforations are undeformed; fits tightly against the supply unit housing.
Installation Status: Suspension rods are secure and level; flexible connections are free of twisting or collapse; no rigid tension at the duct connection point.
II. Filter Leak Testing (Core Test: PAO Aerosol Leak Test)
Filter Face Scan: PAO aerosol is introduced upstream, and a photometer scans the entire downstream filter surface to detect micro-leaks or damage in the media.
Frame Seal Leak Test: Focuses on the gasket seal between the filter and the plenum box (a common area for leaks); mandatory for GMP facilities.
Acceptance Criteria: Single-point leakage concentration must not exceed 0.01% of the upstream aerosol concentration; no persistent leak points allowed; any detected leaks require repair or replacement of the high-efficiency filter.
III. Airflow Volume and Velocity Uniformity Testing
Average Outlet Air Velocity: Measure velocity at standardized points below the diffuser plate, calculate actual supply airflow, and compare with design airflow; allowable deviation: -15% to +10%.
Velocity Uniformity: Measure velocity at multiple points below the diffuser plate to avoid excessively high or low local velocities, preventing airflow short-circuiting or dead zones in the cleanroom.
Plenum Static Pressure Test: Check internal static pressure to assess the rationality of airflow distribution from the duct; low static pressure can result in insufficient actual airflow through the high-efficiency filter. IV. Airtightness Testing of Plenum Boxes and Accessories (Plenum Air Leakage Test)
Overall plenum air leakage test: Seal the air outlets and inlets, pressurize the box, and measure air leakage at welds, access doors, bolt holes, and cable entry points. Standard requirements dictate an air leakage rate of ≤1%; controls are stricter for pharmaceutical Grade D/B areas.
Airflow control valve inspection: If the air outlet is equipped with an airflow control valve, ensure smooth operation and a secure locking mechanism; mark the setting position after adjustment.
V. Cleanliness and Airborne Particle Verification (System Integration Test)
After the HEPA air outlet is put into operation, measure the following at the working height beneath the outlet:
Concentration of 0.5μm and 5.0μm airborne particles to verify filter efficiency and compliance with the required cleanliness class (e.g., ISO-7, ISO-8, GMP Grade D).
VI. Additional Optional Acceptance Tests (Common in High-End Projects)
Filter resistance: Measure the initial pressure drop across the HEPA filter and record the value as a baseline for assessing future clogging; the filter must be replaced if the pressure drop exceeds the initial value by 2 to 2.5 times.
Temperature and humidity verification: Check if the supply air temperature and humidity at the outlet meet the workshop design parameters.
Noise testing: Measure noise levels at a height of 1.2–1.5m below the air outlet to ensure that excessive airflow velocity does not cause abnormal noise.