Should data center chemical filters handle fresh air or recycled air?

The gaseous corrosion pollution in the computer room may come from two directions: one is brought in by the fresh air from the outside, and the other is released by itself inside. Whether the treatment location is placed in the fresh air section or the circulating air section is essentially to determine which direction is the main source.

If the judgment is wrong, no matter how well the filter material is selected, the effect may not be ideal. External input dominates, but filtration is only performed in the return air section, which is equivalent to continuous new pollution coming in, and the circulating filtration can only chase it. Internal release is dominant, but it is only processed in the fresh air section, and the indoor concentration will still slowly accumulate. For specific source investigation, please refer to Discussion of why data centers need to assess gaseous corrosion contamination .

Confirm the primary source first

The first step to determine whether fresh air or circulating air is to figure out where the pollution comes from.

Look around the fresh air entrance. If the computer room is close to industrial areas, traffic arteries, sewage treatment facilities or agricultural areas, the fresh air may carry sulfides, nitrogen oxides, chlorides or ammonia. These components enter the computer room with the fresh air and are external inputs.

Look at the internal materials of the computer room. Batteries, packaging materials, detergents, and electronic component packaging materials may release trace amounts of corrosive components under the influence of temperature. This type of source does not pass through fresh air and accumulates directly in the computer room.

Compare detection data from different locations. Taking samples from the fresh air inlet, the return air area of ​​the computer room, and near key equipment can determine whether the pollution is brought in by the fresh air or generated internally. The concentration at the entrance is significantly higher than indoors, and external input is the main cause; the concentration indoors is higher than at the entrance, and internal release is more worthy of attention. For specific sampling methods, please refer to Discussion of sampling points for chemical filter performance verification .

Record changes in working conditions. Adjustments to the proportion of fresh air, seasonal changes, and equipment startup and shutdown will all affect the relative contribution of pollution sources. Data measured only once may not necessarily represent the situation throughout the year.

When external input is obvious, focus on the fresh air section

If testing confirms that external input is the main source, the treatment location should be prioritized in the fresh air section.

The benefits of fresh air section treatment. Block pollution before it enters the computer room to prevent accumulation of pollutants in the computer room and reduce the burden of subsequent cycle filtration. For specific configuration, please refer to Discussion on why MAU needs to configure chemical filtration section .

The location of the chemical filtration section of the fresh air section. Usually located within the air handling unit, possibly after prefiltration, before or after the surface cooler. The specific location should be confirmed based on temperature and humidity conditions and the suitability of the filter material. If there is a risk of droplets behind the surface cooler, the droplets need to be dealt with first. For specific comparison, please refer to Discussion on whether the MAU chemical filter should be installed before or after the surface cooler .

Air volume and resistance must be calculated. The air volume of the fresh air system in the data center is usually large, and the system resistance will increase after adding a chemical filtration section. It is necessary to check the fan margin to confirm that the air supply volume will not be affected. For specific methods, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity usage .

Fresh air section filtration cannot cover internal release. If materials are also released inside the computer room, fresh air treatment can only reduce the contribution of external input, and the indoor concentration may still gradually accumulate.

For internal accumulation or local protection, consider circulating air or area treatment

If the main source is inside the computer room, or the external input has been treated in the fresh air section and still remains, circulating air or regional treatment is more direct.

Return air section treatment. Set up a chemical filter section on the return air path of the computer room to deal with corrosive components in the circulating air. This method is suitable for situations where internal release is continuous and the concentration is not high but accumulated over a long period of time. For specific configuration, please refer to which air handling systems are appropriate for chemical filters to be installed in . Discussion of

Local area processing. If only some cabinets or equipment are sensitive to corrosive gases, you can evaluate setting up chemical filtration sections in local air supply paths rather than treating the entire computer room. This method has small air volume and controllable resistance effects, but it needs to be confirmed that the local airflow path covers the target device. For specific ideas, please refer to Discussion of what localized contamination can be treated by FFU plus chemical filter .

Recirculating filtration cannot compensate for high concentration external inputs. If the concentration of pollutants brought in by the fresh air is very high, circulating filtration can only dilute it but cannot prevent continuous input. In this case, fresh air section treatment is still necessary.

Combination configurations are more common. The actual plan for many computer rooms is to do the main treatment in the fresh air section, and supplement it in the return air section or local areas. Which section bears how much depends on the detection data and system conditions.

System matching and operational verification

Whether dealing with fresh air or recycled air, system-level conditions must be checked.

The resistance superposition must be calculated clearly. When a chemical filter section is added to both the fresh air section and the circulating air section, the total resistance is superimposed. When selecting a fan or calculating the margin of an existing fan, the resistance of each section must be taken into account. For specific methods, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity usage .

Sampling points should cover before and after treatment. Sampling ports are provided before and after the filtration section to facilitate tracking of outlet concentration changes. The fresh air section and the circulating air section should be set separately and should not be judged together. For specific point selection, please refer to Discussion of sampling points for chemical filter performance verification .

The cooling requirements cannot be ignored. Data centers have high requirements for air supply volume. After adding a filter section, it is necessary to confirm that the air volume can still meet the heat dissipation requirements. Cooling capabilities cannot be sacrificed for gas handling.

Maintenance channels must be reserved. The replacement cycle of the chemical filter section is different from that of the particle filter, and the maintenance access and operating space need to be confirmed during the design stage. involving MAU box chemical filter or The system, interface and resistance of the FFU supporting chemical filter need to be checked together during the planning stage.

Project judgment example

A data center computer room had a circuit board corrosion problem, and the initial plan was to add a chemical filtration section to the fresh air section.

After running for a period of time, it was found that the corrosion trend was alleviated but not completely eliminated. Further testing found that trace amounts of sulfide released from some batteries and packaging materials in the computer room accumulated indoors, and the fresh air section filtration could not handle these sources.

Adjustment plan: retain the chemical filtration section in the fresh air section, and add a chemical filtration section for sulfides on the return air path of the equipment room to deal with internal releases. After recalculating the resistance of the two-stage filter, the fan operating point is still within the acceptable range. After adjustment, the indoor sulfide concentration dropped and the corrosion trend was controlled.

This case illustrates: fresh air or circulating air depends on the source of pollution. The two sometimes need to be used together. involving When selecting chemical filter product series , it is recommended to provide the fresh air test data, indoor test results and system conditions to the supplier for verification.

Key points for selection and acceptance inspection

About Aili Industrial’s data center chemical filtration package

The core of the chemical filtration of fresh air and circulating air in the data center is to match the pollution sources, air paths and heat dissipation conditions, and then select the matching processing location and media.

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 data center projects, fresh air detection data, indoor concentration, air volume and installation space can be combined to assist in checking the filtration configuration of the fresh air section or circulating air section. 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 . Provide pollution source judgment, system conditions and heat dissipation requirements when enquiring, which will help confirm the appropriate filtration solution. The specific selection is subject to the technical documents and test results confirmed by the project.