Air Filter Mounting Clips Guide: How to Choose A-Type, P-Type, and C-Type Filter Holding Clips

A filter holding clip has three main jobs:

•Press the filter against the sealing surface

•Maintain gasket compression during operation

•Prevent filter movement caused by vibration, airflow, or maintenance handling

•If the clip is too weak, the filter can loosen.
•If the clip is too stiff, it can damage the filter frame or make replacement difficult.
•If the clip shape does not match the filter depth, the filter may sit unevenly.

Key point: the clip must match the filter type, frame depth, gasket position, and operating airflow.

Our engineers often see this problem in AHU retrofit projects. The customer upgrades from a flat panel pre-filter to a deeper pleated or bag filter, but the old clips remain unchanged. The filter fits into the opening, but the clips do not apply even pressure. After startup, vibration creates small gaps. That is where bypass leakage starts.

The names A-type, P-type, and C-type clips may vary by supplier or region. Some contractors use local names based on the clip shape. Others define them by application.

For a practical B2B selection, it is better to focus on the function:

•How the clip presses the filter

•How much spring force it provides

•What filter depth it can hold

•Whether it is easy to replace during maintenance

•Whether it resists fatigue after repeated use

Below is a useful way to understand the common filter holding clips types used in HVAC filter frames and filter bank assemblies.

A-type clips are commonly used for shallow filters, especially panel filters and pre-filters installed in standard holding frames. They are usually simple spring clips or latch-style retainers that press the filter face against the frame.

Best Used For

•Panel filters

•Pleated pre-filters

•Washable metal mesh filters

•Nylon mesh filters

•G3/G4 pre-filters under older EN 779 references

•Coarse filters under ISO 16890

•MERV 6–8 type pre-filtration sections

Advantages

•Simple structure

•Easy installation

•Fast filter replacement

•Cost-effective for large filter banks

•Suitable for frequent maintenance

•Good for light to medium filter weight

Limitations

•Not ideal for heavy or deep filters

•May provide limited clamping force

•Can loosen if material quality is poor

•Not recommended for high-vibration sections unless reinforced

When to Choose A-Type Clips

Choose A-type clips when the filter is relatively light, the filter depth is not too large, and the application is general HVAC or pre-filtration.

They work well in:

•Commercial AHUs

•Office building HVAC systems

•General ventilation units

•Pre-filter banks

•Equipment intake sections

For deeper filters, check the actual clamping reach and spring force before using A-type clips.

P-type clips are often used when the filter requires stronger and more stable pressure. The shape usually gives more spring travel than a simple flat clip, making it useful for filters with greater depth or thicker frames.

Best Used For

•Bag filters

•Pocket filters

•Rigid pocket filters

•Deep pleated filters

•Medium-efficiency filters

•F-class filters under older EN 779 references

•ePM1 / ePM2.5 filters under ISO 16890

•MERV 11–15 type HVAC filter sections

Advantages

•Stronger holding pressure than many simple clips

•Better resistance to filter movement

•Useful for thicker filter frames

•More suitable for medium filter banks

•Helps maintain gasket contact under airflow load

Limitations

•More expensive than simple clips

•Requires correct clip height and spring angle

•Can be harder to install in tight spaces

•Poor-quality spring steel may lose tension over time

Choose P-type clips when the filter is deeper, heavier, or more likely to move under airflow vibration.

They are often a good choice for:

•AHU medium filter sections

•Industrial ventilation filter banks

•Bag filter holding frames

•Retrofit projects where stronger retention is needed

•Filter systems with frequent fan start-stop cycles

C-type clips are commonly used when the clip needs to wrap, grip, or lock around part of the frame structure. Depending on the design, they can act like a retaining clip, edge clip, or spring clamp.

Best Used For

•Metal frame filters

•Rigid panel filters

•HEPA filter pre-holding sections

•Filter bank frames

•Custom AHU filter slots

•Applications needing stronger edge engagement

•Systems with higher vibration risk

Advantages

•Good edge holding stability

•Can reduce side movement of the filter

•Useful for custom frames and modular filter walls

•Suitable for reinforced installation

•Better mechanical engagement than simple face clips in some designs

Limitations

•Must match the frame profile closely

•Incorrect size can scratch or deform the filter frame

•Not always ideal for very frequent filter replacement

•May require more careful installation

When to Choose C-Type Clips

Choose C-type clips when you need stronger mechanical retention or when the filter frame design requires edge gripping rather than only face pressure.

They are useful in:

•Modular filter bank assemblies

•Industrial AHUs

•Custom OEM equipment

•Heavy-duty ventilation housings

•Applications where filter movement must be minimized

•For HEPA-related systems, clip selection should be handled carefully. HEPA filters often require precision sealing with gasket or gel seal housings. The clip or clamping system must support the required seal without damaging the filter frame.

This table is a starting point. The final choice should be confirmed by actual filter depth, frame profile, gasket design, and system vibration level.

Panel Filters

Panel filters usually need quick and simple holding. A-type clips are often enough if the frame is flat and the filter is lightweight.

For washable metal mesh filters or aluminum filters, check whether the frame is stiff enough to handle repeated clip pressure.

[Link to Panel Filter Page]

Pleated Filters

Pleated filters can use A-type or P-type clips depending on thickness and frame strength.

For shallow pleated filters, A-type clips are practical.
For deeper pleated filters, P-type clips may provide better holding force.

Bag Filters

Bag filters are heavier and may move more under airflow. P-type clips are usually more suitable because they can hold the filter frame more firmly.

A weak clip can allow the bag filter header to shift, especially during fan startup.

Rigid Pocket Filters

Rigid pocket filters need stable support because they are deeper and heavier than standard panel filters. P-type or C-type clips may be used depending on the holding frame.

HEPA Filters

HEPA filters require more careful clamping because the seal is part of the tested performance. For HEPA boxes, terminal housings, or cleanroom systems, the clamping method must create even gasket compression or proper gel seal engagement.

For high-efficiency filters tested under EN 1822 or ISO 29463, the installed condition matters. A certified filter can still fail field leak testing if the frame or clip system creates bypass.