What should I do if the ULPA leak test passes but the cleanliness is not up to standard?

The leak detection passed, but the cleanliness test failed. This situation is not uncommon on site. Many people will be confused: the filter is not leaking and the installation has been done, why do the particles still exceed the standard?

Because leak detection and cleanliness testing answer two questions. Leak detection confirms whether there are local leaks in the filter and installation interface, which is an integrity verification. The cleanliness test measures the concentration of particles in the air in the protected area and is a space status verification. The two are separated by a set of system factors such as air volume, air flow organization, pollution sources, operating status and sampling conditions. If the leak test is qualified, it means that there is no problem with the filter itself and the interface, but the particles in the space may come from other links. For the specific relationship between leak detection and cleanliness, please refer to the relevant instructions on overall efficiency and local efficiency.

First look at the air volume and airflow organization

Air volume is the basis for particle dilution and removal. If the air volume is not enough, no matter how clean the filter is, the particles in the room may not be taken away in time.

Whether the actual measured air volume is within the design range. The unit gear position, valve opening, and filter element resistance will all affect the actual air supply volume. Supporting The system of FFU fan filter unit needs to measure the surface wind speed one by one; the equipment end application is as follows: For the EFU equipment-side fan filter unit , it is also necessary to confirm that the equipment is in normal production status and not in standby or debugging mode.

Is the airflow organization reasonable? Insufficient coverage of the air supply surface, obstruction of the return air path, obstruction of equipment or structural parts, local eddy currents or short circuits will all lead to high particle concentrations in certain locations. If the particle measuring point is arranged in the reflow area or a dead corner, the readings will naturally easily exceed the standard. Problems with air volume and airflow organization need to be upgraded ULPA ultra-high efficiency filter grade cannot solve it.

Investigate pollution sources and personnel activities

Particles may be generated after filtration.

Process equipment produces dust. Mechanical arm movement, transmission mechanism friction, cable wear, and material handling may all produce particles in the protected area. If the dust generation point is downstream of the filter, no matter how high the filtration level is, it cannot stop it. Device-side applications should pay special attention to this.

Impact on personnel operations. Particles will be generated when people come in and out, operating movements, and friction of clothing. The static test is qualified and the dynamic test exceeds the standard, which is often related to personnel activities.

Material in and out. The surface of the material may carry particles, or the material itself may generate dust during the process. Check material flow and protective measures.

Cleaning and maintenance residues. If dust is not cleaned up after construction or maintenance, it may continue to be released for a period of time. The air duct, the inside of the box, and the surface of the equipment are all inspection objects. For specific pollution traceability methods, please refer to the instructions related to the occurrence of fibers and particles downstream.

Review sampling conditions and test methods

Sometimes the problem isn't with the system, but with the test itself.

Is the sampling location reasonable? Are the measuring points positioned to represent the protected area? If the measuring point is close to a dust source or recirculation area, the reading may be higher.

Test whether the status is consistent. The results of static, dynamic, and empty states vary greatly. If acceptance requires dynamic compliance, static data cannot be used to judge.

Instrumentation and sampling methods. Do the calibration status, sampling flow rate, and sampling time of the particle counter meet the method requirements? Readings may vary between instruments.

background concentration. Will the level of external particles in the test environment affect the results? If the background is high, the measurement point readings may be pulled up.

If these conditions are not aligned, the 'not up to standard' conclusion may not be valid. For the specific test sequence, please refer to the relevant instructions on whether to adjust the air volume first or detect leaks first.

Leak detection and cleanliness records should be kept separate

Do not mix the two types of data together when troubleshooting.

The leak detection record corresponds to the filter element number, installation position, scanning path and leak point treatment results. It describes the integrity of the filter body and interface.

The cleanliness record corresponds to the distribution of measuring points, test status, air volume data and operating conditions. What it illustrates is the spatial granular level.

The two types of records are archived separately. When a problem occurs, it can be determined whether it is a problem on the filter side or on the system operation side. involving For the acceptance of HEPA/ULPA air filters , it is recommended that the two types of judgment requirements be clearly stated in the project documents.

Project judgment example

The cleanliness test of a piece of equipment failed to meet the standards, the leak detection results were qualified, and the air volume was within the design range.

During the investigation, we first reviewed the sampling conditions and found that the measuring points were arranged near the opening of the equipment door and were frequently operated by personnel. This position is normal during static testing, and the particles rise during dynamic testing. Further observation revealed that when the door was opened, outside air entered and local airflow was disturbed.

Treatment method: Adjust the position of the measuring point to the center of the protection area, optimize the air flow organization when the door is opened, and strengthen personnel operating regulations. After re-testing, the cleanliness was found to be up to standard. Leak detection records remain unchanged and are filed separately from cleanliness records.

This case illustrates: Passing the leak test only means that there is no problem on the filter side, and the cleanliness depends on the system operation and test conditions. involving HEPA high-efficiency filters have the same troubleshooting logic. The cleaning items of

Selection and Acceptance Checklist

About Aili Industrial’s system troubleshooting cooperation

If the leak detection is qualified but the cleanliness is not up to standard, the problem is often not in the filter itself, but in the system operating conditions or testing methods. This type of troubleshooting requires looking at product parameters, installation records and test data together.

Aili Industry has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing, and can provide ULPA ultra high efficiency filter、HEPA high-efficiency filter and supporting air supply equipment. When the filter is matched with equipment such as FFU and EFU, the air volume, resistance and interface conditions can be checked uniformly during the planning stage. When the cleanliness is not up to standard, leak detection records, air volume data and equipment structure can be combined to help narrow the scope of investigation.

Leak detection results, air volume records and cleanliness measuring point distribution are provided during inquiry or inspection to help confirm the appropriate treatment direction. The specific test methods and judgment standards are subject to the project plan.