Should the chemical filter gasket face the inlet side or the outlet side?

When installing a chemical filter, the location of the gasket often makes people hesitate: on the inlet side or on the outlet side?

There is no fixed answer to this question. Which side the sealing gasket faces depends on where the contact surface of the mounting frame is, how the pressing parts are arranged, and what the product instructions require. There is only one core goal: to press the contact surface between the gasket and the frame evenly to form a continuous seal and prevent air from bypassing the frame. For specific installation inspection, please refer to Discussion of what appearance and labels to check before installing a chemical filter .

Observe the installation contact surface

The first step in determining the orientation of the gasket is to look at the mounting frame.

Contact surface location. There is usually a flat sealing surface on the mounting frame, and the gasket needs to fit against this surface. The contact surface may be on the inlet side, on the outlet side, or on both sides. The gasket should be installed on the side that can correspond to the contact surface.

Seal groove or card groove. Some frames are designed with grooves into which the gaskets fit. In this case, the position of the gasket is determined by the position of the groove and cannot be changed to the other side at will.

Frame flatness. Whether the contact surface is flat, deformed or the solder joints are raised will affect the sealing effect. Check the condition of the contact surface before installation and clean or trim if necessary. For specific verification methods, please refer to Discussion of how chemical filter sizes match existing filter frames .

Old filter reference. If the old filter element is still there, you can observe its sealing position and compression marks. However, the old filter element may have been deformed or installed backwards. It can only be used as a reference and cannot be copied directly. For specific principles, please refer to Chemical filter airflow arrow unclear discussion on how to confirm.

Also check the direction of airflow

The gasket position and air flow direction are two different things and need to be confirmed separately.

See arrows or installation instructions for airflow direction. The airflow arrow on the filter element indicates the direction of air flow. The gasket position is not necessarily in the same direction as the arrow. Some products have a gasket on the inlet side, some on the outlet side, depending on the design.

Installation in the wrong direction may affect the seal. If the filter element is installed backwards, the gasket may not press against the correct contact surface. Even if it can be installed, the sealing condition may not be up to standard. It is recommended to do the sealing check and direction confirmation together.

Composite structures require special attention. Multi-layer composite filter materials have requirements for the order of air flow, and the position of the sealing pad may also be related to the direction of the filter layer. When installing, check according to the product instructions. Do not judge the direction just by the position of the gasket. For specific differences, please refer to Discussion of whether chemical filters can handle both particulate matter and gases .

Check fit and bypass

After the gasket is installed, do not just look at the appearance, but also confirm the actual sealing status.

Pressure uniformity. Are the hold-down parts applying force evenly? Are there any loose spots at the corners and midpoints of the long sides? If it is pressed too loosely, air will leak. If it is pressed too tightly, the outer frame may be deformed or the gasket may be permanently deformed.

Border gaps. Check whether there is any obvious gap between the outer frame of the filter element and the installation frame. The gasket should fit continuously after compression and should not be partially detached.

Bypass inspection. After installation, check the frame bypass according to project requirements. Methods may be fume generation, pressure checks or leak detection per protocol. For specific methods, please refer to Discussion on how to check frame bypass after chemical filter installation .

Outlet concentration verification. If conditions permit, detect the concentration of the target gas outlet after installation to confirm that the sealing status does not affect the treatment effect. For specific sampling methods, please refer to Discussion of sampling points for chemical filter performance verification .

Record installation status

It is recommended to record the gasket position and installation direction.

Record content: product model, batch, installation position, sealing gasket orientation, air flow direction, compression method, inspection results. During subsequent replacement or troubleshooting, the original installation status can be quickly confirmed.

Take photos to keep. Before and after installation photos can help with subsequent maintenance. When the space at the equipment end is tight, it is easy to get confused when replacing the filter element. Having photos will save trouble.

Refer to the record during maintenance. Supporting FFU with chemical filter or For systems with MAU box-type chemical filters , it is recommended that the maintenance records include gasket location and orientation information.

Project judgment example

In a project, the chemical filter was replaced, and the installer found that the sealing position of the new filter element was different from that of the old filter element. The old filter element seal is on the air outlet side, and the new filter element is on the air inlet side.

After initial installation according to the direction of the old filter element, the compression piece could not cover the sealing surface, and gaps appeared in the frame. Reconfirm the installation direction according to the product instructions of the new filter element, and adjust the contact surface between the sealing gasket and the frame to be evenly pressed. The bypass inspection passed and the outlet concentration was normal.

This case illustrates: The orientation of the gasket must be determined according to the installation instructions of the current product and the frame contact surface, and the old filter element cannot be copied.

Key points for selection and acceptance inspection

About Aili Industrial’s sealing packages

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 sealing structure selection, the installation frame form, compression method and operating conditions can be combined to help check the matching of the gasket position and interface.

Related products:Chemical filter product series、MAU box chemical filter、FFU comes with chemical filter . The specific technical documents and test results confirmed by the project shall prevail.