What is the difference between overall efficiency and local efficiency of ULPA?

These are two concepts that are often talked about interchangeably, but they do different things in detection.

Overall efficiency describes the overall penetration of the finished product. Local efficiency , or local penetration, examines the performance of a specific location. One looks at the comprehensive results, and the other looks for specific flaws.

Why so detailed? Because the overall qualification cannot exclude a single leakage point. Even if a product passes the overall test, there may still be a small leakage in a certain corner. Overall sampling integrates the results from all locations, and small-scale anomalies may be diluted by large low-penetration areas. Partial scanning is designed to find such problems.

The significance and limitations of overall data

The overall efficiency test examines a complete filter and measures its overall removal ability of test particles.

Its value lies in reflecting the overall performance of the product under test conditions. The efficiency data on the report should be viewed together with the test air volume, detection method and particle conditions. A single percentage cannot tell the whole story.

Its limitation is that it cannot be located. If the overall efficiency is low, the report won't tell you where the problem lies - whether it's the filter material itself, a defective edge seal, or damage in one area. At this time, local detection is needed to supplement.

The overall efficiency is usually tested according to MPPS conditions. For specific methods, please refer to the relevant instructions of MPPS. For bulk purchases, overall efficiency is typically provided on a per-lot or contract basis.

Which locations do local scans check?

Local efficiency, or local penetration, is assessed by scanning for leak detection.

The detection scope should cover:

• The filter material surface is scanned according to the path and speed specified in the plan.

• The junction between the filter material and the frame, which is the position of the glue filling line

• Sealing surface of frame and mounting frame

• Accessible cabinet seams

Testing methods and judgment standards should be implemented in accordance with applicable specifications and contract requirements. The probe, scanning speed, aerosol conditions and judgment limits must match the grade requirements of the product.

The data form of local inspection is usually a scanned image or a point-by-point record, with the location and reading of the leakage point marked. This is more valuable than a pass or fail conclusion - it tells subsequent maintenance personnel where the problem is and whether the treatment is in place. For specific troubleshooting methods, please refer to the relevant instructions for on-site leak detection.

How are efficiency and penetration rate related?

Under the same measurement caliber, the efficiency is equal to one minus the penetration rate.

For example: an efficiency of 99.9995% corresponds to a penetration rate of 0.0005%, which is 5 parts per million. The efficiency is 99.99995%, which corresponds to a penetration rate of 0.00005%, which is five ten millionths.

The very low penetration level requires high sensitivity of the detection instrument. Zero counts do not equate to absolutely no penetration, it is possible that the penetration level is below the detection capability of the instrument's current method. Therefore, when interpreting the report, it is necessary to look at the applicability of the instrument range, background control and test method, and cannot simply interpret 'zero' as 'none'.

Supporting FFU fan filter unit or For the ULPA used in the fan filter unit at the EFU equipment end , the interface sealing must be included in the local leak detection after installation. involving For HEPA/ULPA air filter products of different grades, the instrument range and judgment limits should be confirmed according to the corresponding standards.

Project judgment example

A certain ULPA passed the overall inspection, but during on-site scanning it was found that there was a stability abnormality in one corner.

At this time, you cannot ignore this missing point just because the overall result is qualified. Overall qualification indicates that the product meets the requirements at a comprehensive level, but local leaks are still actual defects. The treatment method is to locate this location, determine whether it is a filter material problem, an edge sealing problem, or an installation interface problem, then deal with it in a targeted manner, and re-inspect it after treatment.

If this position belongs to the interface seal, the treatment direction may be to adjust the compression structure or replace the seal; if it belongs to the filter material or edge sealing, the filter element may need to be replaced. The two situations are handled differently and should be reported separately.

Selection and Acceptance Checklist

About Aili Industrial’s testing cooperation

Overall efficiency and local leak detection, one looks at the overall situation and the other looks at the location. The two complement each other in project acceptance.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide ULPA ultra-high efficiency filter and supporting air supply equipment. Testing data, filters and When the FFU fan filter unit and EFU are delivered together, the scope of the whole machine inspection and filter element inspection can be checked uniformly to avoid omissions.

When enquiring, clarify the overall efficiency and local leak detection requirements, judgment standards and reporting forms, which will help with subsequent acceptance. The specific testing methods and judgment standards are subject to the project plan.