What local contamination can FFU plus chemical filter handle?

FFU is a common air supply equipment in clean rooms and local clean areas. Its standard configuration is a fan plus particle filter, which is responsible for controlling particulate matter in the air. But in some cases, particle control alone is not enough – gaseous pollution also needs to be dealt with.

Installing a chemical filtration section on the FFU can process target gases in the circulating air flow. But what kind of pollution can be treated and how effective it is depends on whether the filter material is suitable for the target gas, whether the polluted air flow will pass through the filter section, and whether the circulating air volume matches. The effect cannot be judged only by the FFU coverage area. For specific selection logic, please refer to which air handling systems are appropriate for chemical filters to be installed in . Discussion of

Confirm whether contamination can enter the filter section

This is the prerequisite for judging whether the FFU plus chemical filter is effective.

Internal release source. If the contamination comes from equipment, materials or personnel activities in the area served by the FFU, the circulating air flow will bring these gases into the FFU air inlet, and then return them after being processed by the filter section. In this scenario, the chemical filtration section can continuously reduce the gas concentration in the area.

external input. If the pollution mainly comes from external fresh air or adjacent areas, FFU circulation filtration can only deal with the pollution that has entered the area and cannot prevent the continued input of external pollution. In this case, you need to set up filtering at the fresh air section or area boundary at the same time. For specific differences, please refer to Discussion on why MAU needs to configure chemical filtration section .

Airflow paths need to be confirmed. If the pollution source is downstream of the filtration section, or the airflow bypasses the FFU and diffuses directly to the protected area, the effect of the filtration section will be compromised. Before installation, it is necessary to understand the air flow organization in the area and confirm that the polluted air flow will pass through the filter section. For specific troubleshooting methods, please refer to Discussion on how to check frame bypass after chemical filter installation .

Distinguish between particles and gases task

After FFU adds a chemical filter, there are two types of filtration tasks in the system.

Particle filtration. The original HEPA or ULPA continues to be responsible for particle control. The particle filter efficiency and sealing requirements remain unchanged. For specific differences, please refer to Discussion of the difference between chemical filters and HEPA filters .

Gas filtration. The chemical filtration section is responsible for processing target gases. The media type is selected based on the gas composition, and the capacity and replacement cycle are determined based on the inlet concentration and air volume.

Both properties need to be checked and verified separately. Just because a chemical filtration section is installed does not mean particle control has been upgraded; conversely, HEPA or ULPA efficiency data cannot indicate gas treatment capabilities. The two types of indicators are tested separately during acceptance.

Review wind speed and clean air flow

After installing a chemical filtration section, the system resistance will change and the wind speed needs to be rechecked.

The impact of new resistance. The chemical filtration section increases the total system resistance. If the fan margin is insufficient, the air volume may decrease, affecting the air supply volume in the clean area. For specific accounting methods, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity consumption .

Wind speed uniformity. After adding a filter section, the wind speed distribution on the air outlet surface may change. If the filter section is improperly installed or the media is unevenly distributed, local wind speed may be high or low. For specific measurement methods, please refer to Discussion on how to check the target wind speed after FFU is equipped with a chemical filter .

Leak detection and sealing. After installing the filter section, the sealing status of the FFU needs to be re-confirmed. Frame bypass and filter element displacement may affect the outlet air quality.

Maintenance arrangements. The chemical filter section has a different replacement cycle than the particle filter. Maintenance access and operating spaces should be confirmed during the design stage. Device-side applications such as FFU matching chemical filter , interface and resistance need to be checked together during the planning stage.

Applicable scenarios and limitations

There are several judgment dimensions for which scenarios FFU plus chemical filters are suitable for.

Suitable scenarios:

• There is continuous, low-concentration gaseous pollution release in the area

• External input has been processed in the fresh air section, supplemented by circulating filtration

• The protection target is sensitive to specific gases and requires local strengthening treatment.

• The space allows for additional filter sections and there is room for fans

Scenarios that require additional evaluation:

• The source of pollution is strong and the concentration is high, so circulating filtration alone may not be enough.

• External input dominates, new wind needs to be dealt with first

• The space in the area is tight, and installing a filter section affects maintenance or wind speed.

• There are many types of target gases, and it is difficult to cover them with a single medium.

Processing capabilities cannot be judged solely by FFU coverage area. The treatment effect depends on the suitability of the filter material for the target gas, the circulating air volume and the inlet concentration. For specific selection methods, please refer to Discussion on whether the chemical filter air volume should be selected based on the total air volume of the system or the air volume of a single unit .

Project judgment example

In a certain precision assembly area, a small amount of organic solvent volatilizes inside the equipment. The particles in the area are well controlled, but an odor can occasionally be smelled.

The preliminary plan considered adding chemical filtration in the fresh air section, but testing found that the concentration of organic matter in the fresh air was very low, and the main source was indoor equipment.

Adjustment plan: Install a chemical filtration section for organic gases on the FFU to process solvent volatiles in the circulating air flow. Before installation, the FFU fan margin was calculated to confirm that the air volume could be maintained; a thin chemical filter section was selected to adapt to the internal space of the FFU. After installation, the outlet concentration and area odor were detected to confirm that the improvement was obvious. The filter section replacement cycle is scheduled according to operating data.

This case illustrates: FFU plus chemical filter is suitable for treating gaseous pollution that is continuously released in the area. involving For the configuration of the chemical filter product series , it is recommended that the source of pollution, air flow path and system conditions be provided to the supplier for verification.

Key points for selection and acceptance inspection

About Aili Industrial’s FFU chemical filtration package

The core of FFU plus chemical filter is to match the local pollution characteristics, air flow path and system conditions, and then select the matching media and structure.

Aili Industrial has independent manufacturing capabilities in filters, motors, fans, control systems and sheet metal processing, and can provide chemical filter product series and supporting air supply equipment. For projects that require local circulation filtration, the target gas, concentration, circulation air volume and installation space can be combined to assist in checking the filter section configuration and resistance impact. When the filter is matched with equipment such as FFU and EFU, the interface, maintenance method and sampling point can be confirmed uniformly.

Related products:Chemical filter product series、FFU matching chemical filter、MAU box chemical filter . Providing local contamination information, airflow conditions and system requirements at the time of inquiry can help confirm the appropriate filtration solution. The specific selection is subject to the technical documents and test results confirmed by the project.