Matching a Discontinued Air Filter: What to Send When the Original Part Number No Longer Exists

When an air filter part number disappears from the catalogue, that does not mean the filter itself is impossible to replace. In many cases, the best path is to work from the existing filter, the housing and a few clear photos so a manufacturer can recreate the right fit and performance.

For facility managers, contractors and industrial buyers, the key is to send information that describes the filter as it is installed in the equipment, not just the old SKU. That approach reduces guesswork and helps avoid ordering a filter that is close on paper but wrong in the frame, depth, seal or airflow direction.

Why the old part number is only the starting point

A discontinued SKU can be useful, but it is rarely enough on its own. Over time, the original filter may have changed shape through use, a housing may have been modified, or the old part number may have covered more than one build variant.

A reliable replacement depends on the physical details that affect fit and function, including:

• •Overall dimensions of the filter
• •Frame type and frame depth
• •Seal arrangement
• •Media type and pleat style
• •End cap material and construction
• •Any header, flange, gasket or gel seal detail
• •Airflow direction and orientation in the housing

If you only have the part number, the best next step is to gather supporting information before ordering a replacement. If you are unsure what details matter most, our how to measure an air filter guide is a helpful place to start.

Send a sample if you still have one

If the existing filter is still available, send the physical sample whenever possible. Even a used filter can tell a manufacturer a great deal about the original build.

Before sending it, check whether the filter has been cut, compressed or damaged in storage. If it has, note that in your request so the manufacturer can allow for it.

Useful sample details include:

• •The filter as removed from the system
• •Any labels, handwritten notes or markings still visible
• •Photos of the front, back and side profile
• •Close-up photos of the seal, gasket, frame corners and media pack
• •A note on whether the filter sits loose, tight or flush in the housing

If the filter is fragile or contaminated with heavy dust load, package it carefully so it stays intact during transit. A clean, undistorted sample gives the best chance of a precise match.

Photos that make matching much easier

Clear photos can be just as important as the sample itself, especially if the original filter has already been discarded.

Take photos in good light and include a ruler or tape measure in at least one image. Try to show the whole filter and the installation context, not just the face of the media.

The most useful photos are:

• •The filter on a flat surface, from the front and rear
• •The filter inside the housing, if accessible
• •The filter removed, showing how it seats into the frame
• •The latch, clip, track or access door that holds it in place
• •Any airflow arrows, labels or handwritten notes
• •The filter bank layout if there are multiple filters installed together

If the filter is part of a larger system, a photo of the surrounding plant room or rooftop unit can help identify whether it is a standard panel, bag, pleated cartridge, insert or custom-built filter.

Measure the housing, not just the old filter

A replacement should suit the housing it sits in, not only the dimensions of the worn or compressed sample. Housing measurements are especially important when the original filter is no longer available for comparison.

Measure the available opening and note:

• •Exact width, height and depth of the slot or frame
• •The depth available for the media pack or bag length
• •Whether there is room for a gasket or compression seal
• •The location of supports, rails, clips or retainer bars
• •Access restrictions that may affect installation and removal

If the system has side access, front access or a drawer-style frame, mention that as well. Small differences in frame design can determine whether the replacement fits properly and seals as intended.

When a measurement is hard to take because the filter is still in service, note that too. A manufacturer can often work with partial measurements and photos to narrow down the options.

Details that help identify the right construction

Once the basic dimensions are known, the next step is to describe how the filter is built. That is especially important when a discontinued SKU originally covered several versions or when the application needs a specific media or seal arrangement.

Include any details you can confirm about:

• •Media type, such as synthetic, glass fibre or pleated material
• •Frame material, such as cardboard, galvanised steel, aluminium or plastic
• •Seal type, such as gasket, gel, header or dry seal
• •Whether the filter is panel, pleated, bag, deep-pleat or rigid
• •Temperature or moisture conditions in the system
• •Dust type in the area, such as general dust, lint, paint overspray or fine process dust

If the filter is used in a commercial ventilation system, the site requirements should be confirmed with the mechanical services engineer or building owner. For ventilation applications, AS 1668.2:2024 may be relevant, but the correct selection still depends on the specific installation.

If the original is missing, use the surrounding equipment clues

Sometimes the filter itself is long gone. In that case, the best information often comes from the unit around it.

Look for model plates, cabinet labels, service stickers or maintenance notes on the equipment. If the filter is part of a larger system, the housing may reveal more than the lost part number ever did.

Helpful clues include:

• •Equipment make and model
• •Cabinet or AHU dimensions
• •Filter access door location
• •Number of filters in the bank
• •Orientation of airflow through the unit
• •Any remaining spare filters on site

You can also compare the old SKU against past maintenance records, but treat those records as a guide rather than proof. A filter supplied years ago may have been substituted, updated or built to a site-specific requirement.

When a custom replacement is the best option

If the discontinued filter is unusual in size, seal type or frame construction, a custom air filter may be the simplest and most accurate solution. That is often the case when equipment has been adapted over time or when the original supplier no longer offers the exact build.

A custom approach can help when you need:

• •A non-standard size
• •A specific gasket or frame style
• •A deeper or shallower profile than current stock
• •A special media arrangement for the application
• •A direct replacement for a legacy housing

Some filters are designed to be washable - check the product instructions before attempting to clean and reuse them. If you are unsure whether a filter should be replaced or serviced, our filter servicing and commercial filter servicing pages may help you plan the next step.

What to send with your enquiry

To speed up the matching process, send as much of the following as you can:

• •The old part number, if known
• •A physical sample, if available
• •Photos of the filter and housing
• •Exact measurements of the filter and opening
• •Equipment make, model and serial details
• •Any notes about airflow direction, seal type or installation issues
• •The site address or project location for context

If you are replacing multiple filters across a site, it can help to group the information by area or unit so each filter can be matched correctly.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD, established 2009. If you have a discontinued filter to match, we can help assess the sample, photos and housing details and guide you to the right replacement.

Call 07 3800 3448 or request a quote. You can also explore custom air filters or browse our products to see the types of filters we supply.