What should I do if the ULPA factory and on-site test results are inconsistent?

This situation is not uncommon in projects: the factory report shows that it is qualified, but the on-site leak test fails; or the factory data is very good, but the on-site test shows a significant gap.

Don't rush to the conclusion that it's a product problem, and don't directly conclude that it's an on-site operation error. The objects, conditions and methods of factory inspection and on-site inspection and verification may be different. First check where the difference comes from, and then determine which link the problem lies in.

Establish comparable test conditions first

To compare two test results, the conditions must be comparable.

Detect object. The factory inspection may test the single filter, and the on-site inspection also includes the box, frame and sealing interface. The two coverage areas are different, and the results cannot be directly compared.

Test air volume. Is the air volume on the factory report consistent with the on-site operating air volume? If the on-site air volume deviates from the design value, the interpretation of the test results will be different.

Aerosols and Instruments. Are the aerosol types, generation methods, and testing instruments used for factory testing the same as those used on site? Readings from different methods cannot be directly compared.

Sample flow and location. Depending on the sampling parameters, the results may be different. Please indicate this when recording.

background concentration. Background particle levels in field environments may be higher than in the laboratory, affecting the interpretation of readings.

Only when these conditions are aligned can we judge whether the difference between the two results is a real difference.

Retesting requires stability

If differences are found after the initial comparison, retesting is necessary. The prerequisite for retesting is stable conditions.

The air volume is stable. Keep the fan gear and air valve opening stable to avoid fluctuations caused by automatic speed adjustment or operating mode switching.

The upstream concentration is stable. After aerosol generation and mixing reach a stable state, detection is started and the upstream concentration is recorded.

Instrument status confirmation. Check the calibration validity period, zero point status and span suitability.

Background check. Confirm the background level before testing and explain the impact of background on the results if necessary.

Occasional reading peaks should be reviewed according to the test method, and the location and time should be recorded. A product cannot be judged to be unqualified based on one exception, nor can repeated exceptions be ignored. involving For HEPA/ULPA air filter products of different grades, the testing methods and criteria are implemented in accordance with the corresponding standards, and the instrument range must match the grade requirements.

From differences to problem positioning

If the difference still exists after retesting, you can start to locate the problem.

If the abnormality is concentrated on the filter material surface. Check whether the filter material is damaged, whether the pleats are deformed, and whether the edge sealing is complete. Such problems may be related to shipping, handling or installation operations.

If the exception is centered on the border or interface. Check the gasket condition, compression method, frame flatness and tank fit. Such problems often lie in the installation process, rather than the product itself. For specific troubleshooting ideas, please refer to the instructions on inspection after reverse installation and gasket compression.

If the abnormal distribution has no obvious pattern. Check whether the air volume is stable, whether the detection method is consistent, and whether the instrument is normal. It may also be necessary to review the test conditions of the factory data.

After rectification, retest under the same conditions. Don't just change the report. Supporting FFU fan filter unit or For the system used by the fan filter unit at the EFU equipment end , the boundaries between complete machine testing and filter element testing must be confirmed clearly before investigation.

Project judgment example

The filter surface of a certain ULPA passed the factory inspection, but during on-site leak detection, the edge continued to exceed the limit.

In this case, neither the factory report nor the on-site results are wrong - they have different detection ranges. The factory report is for the filter element body, and the on-site leak detection also includes the sealing interface between the filter element, the frame, and the box. If the edge exceeds the limit, the problem may be in the gasket, compression structure or frame fit, not necessarily the filter material itself.

The treatment direction is to check these interface parts first, rather than directly determining that the filter element level is insufficient or requiring replacement. If the retest passes after adjusting the interface, it means that the problem lies in the installation process; if the retest still fails, then evaluate the status of the filter element itself.

Selection and Acceptance Checklist

About Aili Industrial’s testing cooperation

The difference between factory and on-site testing often comes from the differences in testing boundaries and methods. By aligning the conditions on both sides, the problem will be easy to locate.

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 complete machine inspection and filter element inspection can be checked in a unified manner to reduce the situation where the data on both sides are inconsistent.

Clarifying the testing methods, testing conditions and reporting forms when making inquiries will help with subsequent acceptance correspondence. The specific testing methods and judgment standards are subject to the project plan.