What to Consider When Retrofitting Filtration in an Older GP Clinic

Retrofitting filtration in an older GP clinic is rarely as simple as swapping one filter for another. Older buildings often come with tight plant rooms, limited access, legacy housings and a mix of equipment installed over many years, so the first step is understanding what is actually on site before ordering parts.

For facility managers, contractors and property owners, a careful approach helps avoid delays, repeat visits and poorly fitting filters. It also makes it easier to match the right product to the system, the space and the maintenance routine already in place.

Start with what is installed, not what the drawing says

In older medical centres, the as-built records may not match what is physically in the plant room. Ductwork may have changed, housings may have been replaced, and access panels may have been altered during previous works.

Before selecting replacement filters, confirm:

• •the exact filter housing type
• •the filter depth, face dimensions and sealing arrangement
• •the direction of airflow
• •whether the filters are single-stage or part of a staged system
• •whether there are access constraints for removal and installation

If you are unsure how to measure what is there, use how to measure an air filter as a starting point. For older sites, a measured check on the existing filter frame or housing is usually more reliable than relying on old paperwork alone.

Legacy housings can limit your options

Many older GP clinics use housings that were designed around discontinued sizes or older filter formats. In those cases, the challenge is not just finding a filter that fits the opening, but finding one that seals properly and can be installed without forcing the frame.

Common issues include:

• •non-standard lengths or depths
• •damaged gasket surfaces
• •bent frames or retaining clips
• •limited clearance for holding frames, bags or cassettes
• •corrosion or wear around the housing edges

If the housing is in poor condition, replacing the filter alone may not solve the problem. A mechanical services engineer or building owner may need to assess whether the housing should be repaired, adapted or replaced.

Tight plant rooms need a practical installation plan

Older clinics often have plant rooms that were never designed for today’s maintenance access needs. That can make even a straightforward filter change awkward, especially when there is little working room around the unit, low ceiling clearance or poor lighting.

Check access before the job starts

Good planning can save a lot of time on site. Before bringing in new filters, check:

• •whether there is enough room to remove the old filter without damaging adjacent parts
• •whether doors, ladders or panels allow safe access
• •whether the filter can be inserted and seated correctly from the available position
• •whether temporary shutdowns will affect adjacent areas
• •whether replacement filters need to be handed up, passed through a narrow opening or installed in stages

If the plant room is particularly constrained, you may need filters with a frame or format that can be handled more easily in tight spaces. our products page gives an overview of the types we supply, including options for commercial applications.

Don’t overlook the surrounding equipment

When a plant room is crowded, it is easy to focus only on the filter slot. In practice, nearby pipework, control gear, insulation, cable trays and access doors can affect how a filter is installed and maintained.

A good retrofit check should confirm that the filter can be removed straight out of the housing, or that there is enough flexibility to angle it clear without tearing media or dislodging seals. If that is not possible, the maintenance process may need to be adjusted before the new filters are specified.

Non-standard filter sizes are common in older clinics

Older medical centres often contain filters that were made to suit a particular unit or housing rather than a common stocked size. That can make replacement more difficult, especially if the original supplier no longer supports the format.

When you are dealing with a non-standard size, it helps to gather as much detail as possible:

• •overall length, width and depth
• •frame material and profile
• •seal type and position
• •any part numbers or labels on the housing
• •the number of filters used in the bank or unit

If the filter is unusual, custom air filters may be the most practical route. A custom-made replacement can help match the existing housing without forcing a change to the ductwork or cabinet.

Avoid guessing on dimensions

A filter that is only slightly off in size can create problems with sealing, rattle, bypass or difficulty fitting the frame into the opening. In a busy clinic, that can quickly become a maintenance issue.

Where possible, measure the actual opening and the existing filter, and check for wear that may have altered the fit over time. If the old filter is compressed, warped or damaged, take extra care not to copy an incorrect dimension from a distorted part.

Match the filter to the application, not just the opening

An older clinic may have several areas with different filtration needs. For example, one air handling unit may serve waiting rooms, consult rooms and corridors, while another may support a treatment area or back-of-house space. The right filter choice depends on the equipment, the expected dust load and the intended level of filtration in the system.

If the ventilation system has been updated, check whether the current setup still aligns with AS 1668.2:2024 and confirm site requirements with the mechanical services engineer or building owner. That is especially important where retrofit work has changed airflow, pressure drop or maintenance access.

Pressure drop matters in older systems

Older fans and housings may have less tolerance for higher resistance than newer systems. If you move to a different filter type, the pressure drop should be checked so the unit still operates as intended.

Where gauges are fitted, monitor them during operation and at service visits. The inspection frequency depends on the system, site conditions and dust load, and you should follow the filter and equipment manufacturer instructions. For some sites, the practical maintenance cycle may change with seasonal dust, renovation work nearby or changes in clinic occupancy.

Consider the maintenance routine as part of the retrofit

Retrofitting filtration should make future servicing easier, not harder. If the filters are awkward to access or the housing is already difficult to open, maintenance may become inconsistent over time.

A good retrofit plan should consider:

• •whether the replacement filter can be installed without special tools
• •whether the sealing method is clear and repeatable
• •whether the staff responsible for maintenance can access the unit safely
• •whether spare filters can be kept on hand in the correct size
• •whether the housing would benefit from repair before new filters are fitted

Some filters are designed to be washable - check the product instructions. For most commercial sites, though, the key point is not washability itself but whether the chosen product suits the housing and the maintenance process.

If you need ongoing support, filter servicing and commercial filter servicing can help keep the system easier to manage over time.

What to do before you place an order

Before ordering replacement filters for an older GP clinic, make sure you have confirmed the following:

• •the exact dimensions and fit of the existing filter
• •the housing condition and access path
• •whether the size is standard or custom
• •the filtration level required for the system
• •any pressure drop or airflow constraints
• •whether the site needs a housing repair or adaptation

It is often worth taking photos of the filter in place, the label on the frame and the surrounding housing. That information can save time if you need to compare options or order repeats later.

If the existing setup is difficult to describe, you can also speak with a supplier that works with older commercial systems and can help identify the best replacement path.

Need help with an older clinic retrofit?

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD. We can help supply or make the right filters for older clinic housings, including custom sizes and practical replacement options for awkward plant rooms.

Call 07 3800 3448 or request a quote. You can also browse our products or contact us if you need help working out what will fit.