How to choose HEPA filter for high humidity environment?

When choosing HEPA in a high-humidity environment, a common misunderstanding is to only focus on one humidity number.

Ask the supplier 'How high humidity can your filter element withstand?' and the answer you get is often a range of values. However, in actual working conditions, continuous high humidity, short-term condensation, and cleaning water splashing onto the filter element are three different things, and the requirements for the filter are also different. Before selecting a model, it is more meaningful to first understand how moisture contacts the filter element than to directly ask about the moisture resistance index.

First distinguish what type of moisture risk is

Laboratories, pharmaceutical workshops, food processing, and some semiconductor processes may all encounter high humidity conditions, but the causes are different.

Continuous high humidity : The relative humidity of the environment is high for a long time, and the filter material and edge sealing material are in a hygroscopic state. In this case, attention should be paid to the stability of the material under the target temperature and humidity, and whether the resistance will change with moisture absorption.

Short-term condensation : When the temperature and humidity fluctuate or the equipment starts and stops, the surface temperature of the filter element is lower than the dew point, and moisture condenses on the filter material. This risk has little to do with average humidity, but rather depends on the magnitude and frequency of temperature changes.

Direct contact with water : Cleaning operations, pipeline leaks, and poor drainage cause water droplets to splash or drip onto the filter element. This kind of situation has exceeded the applicable scope of conventional HEPA, and protective structures or front water-blocking measures need to be considered.

The three types of risks correspond to different selection directions. If you treat short-term condensation as continuous high humidity, you may not be able to select the right point; if you treat direct water spray as ordinary high humidity, the life of the filter element will be significantly shortened.

The filter material, edge sealing glue and outer frame should be looked at separately.

The moisture resistance of the filter is not determined by a single material. Several parts have their own boundaries.

Filter material : Different materials have different hygroscopicity and wet strength. The performance changes of glass fiber filter material under high humidity are different from those of PTFE filter material. When selecting, you should confirm with the supplier the applicable conditions of the filter material under the target temperature and humidity, rather than just looking at the efficiency data at normal temperature and humidity.

Edge sealing glue : The glue line between the filter material and the frame may age and crack if exposed to high humidity environment for a long time, causing leakage points. This kind of problem may not appear immediately during routine leak detection, but will be exposed after running for a period of time.

Outer frame and gasket : Anti-rust treatment should be considered for the metal outer frame, and the rebound performance of the gasket material after moisture absorption should be considered. If the outer frame deforms due to changes in humidity, the contact state of the sealing surface will also change.

These items should be checked together, not just about the filter material. Specific material selections can be combined with HEPA/ULPA air filters . Product information and operating conditions confirmation of

Simultaneously evaluate resistance and preamp

Moisture may cause changes in the filter material and sealing status, and also affect the system resistance.

If the filter is in a high-humidity environment for a long time, the resistance change trend is different from that in a dry environment. It is recommended to consider front-stage dehumidification, drainage and filtration maintenance simultaneously when designing the system: once the front-stage filtration is done, the burden on the terminal filter element will be much smaller; if dehumidification is in place, the risk of condensation will also be reduced.

For matching When the FFU fan filter unit is used, the fan operating point must be rechecked according to the wet resistance to avoid the air volume declining beyond expectations after running for a period of time. Device-side applications such as The EFU equipment-end fan filter unit has a compact internal space. If the equipment itself has the risk of condensation, the installation location and protection method of the filter element need to be considered together.

Leave comparable records during operation

After installation, establish pressure difference and air volume benchmarks. When water stains, deformation or abnormal pressure differences are found, on-site leak detection and product instructions are combined to determine the treatment method.

There is an easily overlooked point here: just because the filter element is dry on the outside, it does not mean that there is no problem with the internal pleats and glue lines. If there has been an obvious moisture or condensation incident, even if the appearance returns to normal, it is recommended to re-inspect according to the project requirements instead of continuing to use it directly.

About Aili Industrial’s supporting equipment for high humidity conditions

Aili Industry can discuss the material and structural configuration of the filter based on temperature, humidity, gas environment and installation space. Since filters, fans, control systems and sheet metal are in the same manufacturing system,FFU fan filter unit and The complete solution of the fan filter unit at the EFU equipment end can be confirmed together with the filter element material, instead of ordering the filter element first and then looking for supporting equipment.

For projects in high-humidity conditions, it is recommended to provide the continuous temperature and humidity range, temperature fluctuation range, whether there is a risk of condensation or water dripping, as well as the installation location and operating time, so as to facilitate the judgment of the applicable conditions of the filter material, edge sealing and sealing structure. Special working conditions need to be clearly defined in the technical confirmation document, including continuous, peak and detection conditions. Specific performance is subject to product technical data and project acceptance results.