What are the symptoms of HEPA filter air leakage?

Air leakage is often not something that can be seen at a glance.

The filter is installed on the ceiling or in the equipment and cannot be seen or touched when in operation. When an abnormality is discovered, it is often caused by the room particle monitoring alarm, or the regular leak detection fails. Before that, there are actually some indirect signs that you can refer to.

These signs cannot directly prove air leakage, but they can indicate 'this location needs to be checked'. By comparing the signs with the leak detection results, the troubleshooting efficiency will be much higher.

Abnormal leak detection readings are the most direct signal

During regular leak detection, if the reading at a certain location is higher than that at other locations, or the same product passed the test last time but failed this time, it is worth paying attention to.

Local abnormal point : The reading increases when the probe passes a certain location during the scanning process, and recovers after leaving. This location is a candidate for missing points.

The same position that reappears : the leak was marked last time and reappeared after treatment, indicating that the previous treatment was not thorough, or there is a problem with the frame structure itself.

The entire edge or a certain corner is abnormal : continuous readings along a section of the sealing edge are high, and the investigation direction is different from that of a single leak. The corners of the liquid tank sealing structure are prone to problems. For specific verification methods, please refer to the relevant instructions on knife edge size verification.

Traces of dust can provide clues

The distribution of dust around the filter can sometimes reflect the direction of the airflow.

There are dust marks near the frame : When the air bypasses the frame, it may cause particles to be deposited near the sealing surface. If there are obvious dust marks on a corner or edge, but other areas are clean, this area is worth checking.

The surface color of the filter material is uneven : the color is darker in some areas, which may indicate that the air volume passing through this area is too large, or unfiltered air is mixed in.

There is dust accumulation near the gasket : there is no place for the gasket to compress, and air will leave marks as it bypasses.

These signs are not direct evidence of an air leak, as dust accumulation can come from other sources as well. However, looking at the leak detection results together can help locate the problem.

Changes in particle monitoring data

For particle monitoring in a room or equipment, if the following conditions occur, air leakage can be included in the scope of investigation.

High concentration at a single point : The number of particles at a certain measuring point is continuously higher than that of the surrounding areas, and it is not caused by human activities or material entry and exit.

After replacing the filter element, it does not go down but rises : after the new filter element is installed, the particle number does not improve or even worsens. In this case, the installation of the seal should be suspected first, rather than the efficiency of the new filter element.

Multiple devices in the same area behave inconsistently : If other devices in the same area are normal but only one device or a certain location is abnormal, the problem is more likely to lie in the installation interface of this device.

involving For products of different grades of HEPA/ULPA air filters , the criteria for particle monitoring may be different. The verification shall be carried out according to the corresponding project documents.

System data can assist judgment

Air volume, pressure difference and fan operation data can also provide reference.

The pressure difference is normal but there are local abnormalities : the pressure difference reflects the overall resistance, and local air leakage is not necessarily reflected in the pressure difference. Therefore, normal pressure difference does not mean that there is no leakage point.

Uneven distribution of air volume : The air volume of a certain unit in the parallel system is low, which may be caused by air leakage at the interface. Supporting For the FFU fan filter unit system, such problems can be found by measuring the surface wind speed one by one.

The fan gear remains unchanged but the air volume decreases : In addition to dust accumulation on the filter element, you should also check whether there is a bypass that reduces the effective air supply volume. Device-side applications such as EFU equipment-end fan filter unit , the internal structure of the equipment may affect the measurement results, and the operating status of the equipment must be recorded when troubleshooting.

When troubleshooting, don’t just look at one signal

Any of the above items alone cannot directly determine air leakage.

Abnormal leak detection readings are the closest to direct evidence, but the effects of instrument status, upstream conditions and operating conditions also need to be ruled out.

Dust traces and particle data are indirect reminders and need to be confirmed with leak detection.

A reasonable approach is to compare the particle count, air volume, pressure difference, leak detection and fan control records on the same timeline. First find out the area and time when the changes occurred, and then arrange targeted inspections. The leak location is ultimately based on the on-site leak detection results , and other data is used to narrow the scope of the investigation.

About Aili Industrial’s air leakage investigation cooperation

Aili Industry covers the production links of filters and air supply equipment, and can help troubleshoot problems by comparing filter element resistance, sealing and overall air volume. filter with FFU fan filter unit、The EFU equipment-end fan filter unit is matched in the same manufacturing system, and the interface size and sealing structure can be uniformly checked during the planning stage.

The processing results should be confirmed by on-site re-testing. The specific testing methods and judgment standards are subject to the project plan.