On-Site Testing Services for Gel Seal HEPA Filters

The on-site testing services for Gel Seal HEPA filters are the ultimate and essential step to ensure the successful installation and long-term reliable operation of these filters. The core of this service is the on-site leak test, which aims to verify the integrity of the filter itself, its gel seal interface with the installation frame, and the entire installation perimeter, ensuring there are no leak points.

Detailed Content of the Service:

I. Purpose and Importance of Testing
1. Purpose: To visually confirm and locate any leaks in the Gel Seal HEPA filter and its installation system, ensuring the air quality in the clean environment meets the designed grade (e.g., ISO 5/Class 100).
2. Importance:
2.1 Quality Verification: A mandatory step for installation project acceptance, proving the success of the installation.
2.2 Risk Control: Prevents the entire clean environment from failing due to micro-leaks, which is a safety baseline for biosafety laboratories and chip factories.
2.3 Performance Assurance: Ensures product yield, experimental accuracy, or operational safety.
2.4 **Responsibility Allocation**: Clarifies installation responsibility (installation issues) and product quality responsibility (filter itself issues).

II. Testing Method: PAO/DOP Aerosol Photometry Scan Leak Test
1. Working Principle:
1.1 Upstream Smoke Generation: In the supply air plenum or duct, a specialized generator produces PAO (Polyalphaolefin) or DOP (Di-2-ethylhexyl phthalate) aerosol particles (typically 0.3-0.5μm) and mixes them uniformly in the airflow.
1.2 Downstream Scanning: Using a high-sensitivity photometer probe on the downstream side of the filter (i.e., the cleanroom side), scan all areas at a distance of about 1-2cm from the filter surface at a speed of <5cm/s, slowly and overlapping.
1.3 Real-time Measurement: The probe continuously draws air, and the photometer measures the aerosol concentration. Any leak point will cause a sharp increase in downstream concentration, triggering an alarm and displaying the leak rate (e.g., 0.01%).
2. Scanning Areas:
2.1 Filter Material Surface: Check for holes or defects in the filter itself.
2.2 Bonding between Filter Material and Frame: Check the sealing process of the filter itself.
2.3 Gel Seal Interface (Most Critical Scanning Area): Scan the entire interface between the filter knife edge and the installation frame’s gel trough, where installation leaks are most likely to occur.
2.4 Frame-to-Frame Connections: Check the overall seal of the installation frames.
2.5 Frame-to-FFU/Ceiling Connections: Check the seal integrity of the entire supply unit.

 III. Technical Service Process
A professional on-site testing service typically includes the following steps:

1. Preparation:
1.1 Confirm Site Conditions: The HVAC system has been running continuously for at least 12 hours and is stable, and the cleanroom has been thoroughly cleaned.
1.2 Equipment Calibration: Calibrate the aerosol generator and high-sensitivity photometer to ensure accurate data.
1.3 Plan Formulation: Confirm the testing scope, standards (e.g., ISO 14644-3), and pass criteria with the client.
2. On-Site Operation:
2.1 Establish Smoke Point: Create a stable aerosol concentration (e.g., 10-20μg/L) in the plenum or duct.
2.2 Baseline Measurement: Measure the aerosol baseline concentration upstream.
2.3 Downstream Scanning: Two technicians work together to scan each filter and all interfaces comprehensively along a predetermined path. The probe movement should be slow and steady.
2.4 Marking Points: Immediately mark any detected leak points with non-dropping adhesive tape.
3. Problem Analysis and Repair:
3.1 Cause Analysis: Determine whether the leak is due to a filter defect, gel sealant filling issue, uneven frame, or loose mechanical clamps.
3.2 On-Site Repair:
3.2.1 For Installation Issues: Minor leaks can be locally repaired with specialized sealant; severe leaks may require removing the filter, cleaning old sealant, and reinstalling with new sealant.
3.2.2 For Product Issues: Replace with a spare new filter.
3.2.3 Re-testing: All repaired points must be re-scanned until fully qualified.
4. Reporting and Delivery:
4.1 Testing Standards and Methods.
4.2 Instrument Models and Serial Numbers.
4.3 Filter Numbers, Locations, and Scan Results (Maximum Leak Rate).
4.4 Locations, Photos, and Repair Records of Non-Conforming Points.
4.5 Conclusion: Clearly state whether the installation area passes the leak test and meets the XX standard/grade.
4.6 Report Interpretation: Explain the report content to the client’s responsible person and archive it as a benchmark for future maintenance.

IV. Pass Criteria
Typically referenced from ISO 14644-3 or GB/T 25915 standards:
For high-efficiency filters (HEPA/ULPA), the leak rate at any point must not exceed 0.01% of the upstream concentration (i.e., for a filter with 99.99% efficiency, the leak point must also not exceed 0.01%). More stringent projects may require a leak rate <0.005%.

V. How to Choose a Technical Service Provider
1. Qualifications and Experience: Select a third-party testing agency with CNAS (China National Accreditation Service for Conformity Assessment) or CMA (Certification of Qualification for Inspection and Testing Institutions) qualifications, and inquire about their experience with similar projects (especially gel seal systems).
2. Equipment Level: Use high-precision, high-sensitivity photometers (e.g., ATI, MetOne) that are within the regular calibration validity period.
3. Personnel Professionalism: Operators should be trained and familiar with the structure of gel seal systems and common leak points, able to accurately diagnose leak causes and provide repair recommendations.
4. Service Scope: Confirm whether the service includes technical guidance or assistance in repairs after issues are found, not just testing and reporting.

The on-site testing service for Gel Seal HEPA filters is not a simple “test” but a systematic quality verification and problem diagnosis process. It is the last and most crucial firewall to ensure that the high-investment clean environment functions as expected. Do not omit or take this test lightly to save costs.