Why does MAU need to configure a chemical filtration section?

The main task of MAU (Make-up Air Unit) is to introduce outdoor fresh air, process it and then send it to the clean room or process area to supplement the air volume taken away by the exhaust air.

Many projects are equipped with primary, medium and high-efficiency filtration sections in the MAU, and particle control is done well, but gas pollution is not treated. Gaseous pollutants in the fresh air—acidic gases, alkaline gases, organic vapors, and external odors—will directly enter the clean area or equipment along with the fresh air. If these components have an impact on the process or equipment, particle filtration alone will not solve it.

This is why MAU needs to be equipped with a chemical filtration section: to control gaseous pollution from the fresh air inlet, instead of waiting for it to enter the clean area and then find a solution. For specific selection logic, please refer to Discussion of what chemical filters are and what problems they are mainly used to solve .

Investigate external input

Before configuring a chemical filtration section, first understand what may be in the fresh air.

nearby emission sources. Industrial parks, traffic arteries, sewage treatment facilities, and chemical companies may all emit gaseous pollutants into the atmosphere. The location of the new air outlet and the surrounding environment directly affect the introduced pollution load. For specific evaluation methods, please refer to The factory is close to the source of pollution, and the discussion on how to match the relocation of the air inlet with chemical filtration is discussed.

Seasons and wind changes. The pollution load may be different in different wind directions and seasons. Consider the most unfavorable conditions when designing, or reserve room for adjustment.

Detection data. Sampling fresh air inlets during representative periods to confirm main gas components and concentration ranges. For specific methods, please refer to whether to do air sampling before choosing a chemical filter . Discuss

Don't judge based on experience alone. Some pollution sources have no obvious smell, but they have an impact on certain processes. Inspection data is more reliable than sensory judgment.

Arrange filter segment location

Where to place the chemical filtration section of MAU should consider the system structure and environmental conditions.

Filter segment order. The common sequence is: initial effect → medium effect → chemical filtration section → surface cooler → heating/humidification → high efficiency. The location of the chemical filter section will affect its working environment.

Front or rear of the surface cooler? The air temperature before the surface cooler is high and the humidity is low; the air temperature behind the surface cooler is low and the humidity is high, and droplets may be entrained. Some chemical media are sensitive to humidity and may require additional water removal measures after being placed in the surface cooler. For detailed discussion, please refer to Discussion on whether the MAU chemical filter should be installed before or after the surface cooler .

Particle pre-filter protection. The dust in the fresh air will cover the chemical medium and shorten the service life. Setting up appropriate particle prefiltration before the chemical filtration section can reduce the media burden. Please refer to the specific division of labor Discussion on the division of labor between chemical filters and primary filters .

Maintenance channel. The replacement cycle of the chemical filter section is different from that of the particle filter section, and maintenance channels must be reserved during the design stage.

Check the operation of the whole machine

Adding a chemical filtration section will change the system resistance, and the operating point of the entire machine needs to be rechecked.

Resistance stacks up. Add the initial resistance and final resistance of filters at all levels, plus the resistance of surface coolers, heaters, air ducts, etc., to get the total resistance of the system. Compare the fan curve to confirm whether the operating point is acceptable under the design air volume. 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 .

Air volume distribution. If the MAU supplies air to multiple areas, the air volume distribution of each branch may change after adding a chemical filter section. It is necessary to recheck the branch air valve opening or adjustment method. For specific balancing methods, please refer to whether chemical filtration modification requires re-doing the air volume balance . Discuss

Seal and bypass. The installation and sealing of the chemical filter section must be reliable. The frame bypass will allow untreated air to bypass the medium, and the outlet concentration will naturally not decrease. For specific inspection methods, please refer to Discussion on how to check frame bypass after chemical filter installation .

Sampling points are reserved. Sampling ports are provided before and after the filtration section to facilitate subsequent tracking of outlet concentration changes.

MAU treatment is not a substitute for other measures

Configuring the chemical filtration section is part of AMC control, but it is not all.

Indoor source. If there is material release or process discharge in the clean room, the MAU handles the fresh air part, and the indoor release also needs to be managed through circulating filtration, local exhaust or source control.

Device-side protection. Some sensitive equipment may require independent local filtration and cannot rely solely on the MAU's fresh air treatment. Device-side applications such as FFU with chemical filter or EFU is equipped with chemical filters , which can be configured separately according to equipment requirements.

The division of labor in the system must be clear. The scope of fresh air treatment, circulation filtration, and equipment end protection should be clarified during the planning stage. All AMC control requirements cannot be placed on the MAU. Please refer to the specific division of labor which air handling systems are appropriate for chemical filters to be installed in . Discussion of

Project judgment example

The fresh air unit of a semiconductor factory was originally equipped with only a particle filter section. After operation, it was found that gaseous pollution occurred in some process areas.

The investigation confirmed that there are chemical emission sources near the fresh air inlet. After the acidic gases and organic vapors in the fresh air entered the clean area, they affected some processes. The particle filtration system is operating normally but has no gas processing capabilities.

Adjustment plan: Add a chemical filtration section to the fresh air unit, and configure separate media for the detected acid gases and organic matter. The filter section is located in front of the surface cooler to avoid the influence of high humidity. The system resistance was recalculated and the fan operating point was confirmed to be acceptable. After the adjustment, the gaseous pollution load of fresh air was significantly reduced, and the problems in the process area were alleviated.

This case illustrates: MAU is equipped with a chemical filtration section to deal with gaseous pollution carried by fresh air. involving When selecting the MAU box-type chemical filter , it is recommended to provide the fresh air detection data and system conditions to the supplier for verification.

Key points for selection and acceptance inspection

About Aili Industrial’s MAU chemical filtration package

The core of the MAU chemical filtration section is to match the fresh air pollution characteristics, system conditions and protection goals.

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 MAU projects, fresh air detection data, air volume, filter section location and replacement space can be combined to assist in checking the media type and structural configuration. When the filter is matched with MAU, FFU, EFU and other equipment, the resistance, interface and maintenance methods can be confirmed uniformly.

Related products:Chemical filter product series、MAU box chemical filter、FFU comes with chemical filter . When enquiring, provide fresh air detection data, system conditions and protection requirements to help confirm the appropriate filter section configuration. The specific selection is subject to the technical documents and test results confirmed by the project.