What to Consider When Upgrading Filters in Older Queensland Office Towers

Older Queensland office towers can be straightforward in plan, but awkward in the plantroom. When filter upgrades are needed, the real challenge is often not selecting a better filter media, but matching old housings, uncommon sizes and restricted access without creating avoidable downtime for occupants and contractors.

For property managers and contractors, a successful upgrade starts with understanding what is already installed, what the system can physically accept, and how the site is maintained. The right filter choice should suit the equipment, the dust load, and the building’s maintenance access — not just the size written on the old frame.

Start with the existing plant, not the catalogue

Older commercial buildings often contain a mix of original and modified mechanical services. That can mean non-standard filter frames, legacy holding systems, or units that have been repaired over time with whatever parts were available.

Before ordering replacement filters, confirm:

• •the exact filter dimensions, including depth, flange style and sealing surface
• •whether the frame is rigid, disposable, bag-style, panel-style or a custom housing
• •how the filter is retained in place
• •whether there is enough clearance to remove and install the filter without damaging seals
• •whether the existing frame is still serviceable or needs repair or replacement

If you are unsure about the dimensions, how to measure an air filter is a useful starting point. Small variations can matter, especially where a tight-fit frame relies on compression to prevent bypass.

In older towers, the original filter may no longer be a standard off-the-shelf size. In that case, custom air filters can be a practical option when the goal is to match existing equipment without major sheet metal changes.

Non-standard frames and ageing housings

Hard-to-source frames are common in older buildings, particularly where equipment was installed before current product ranges became common. A simple replacement can become more involved when the old frame has warped, corroded or been patched.

Signs the frame needs attention

• •visible rust or distortion around the frame edges
• •gaps where air may bypass the filter
• •damaged clips, latches or gasket surfaces
• •a filter that rocks, bows or does not sit evenly
• •repeated dust marking around the frame after changeover

If the housing is not holding the filter securely, a better media grade will not solve the problem. Air can still bypass the filter and pass through the gaps around it. In those cases, it is worth involving the mechanical services engineer or building owner to confirm whether the frame should be repaired, relined or remade.

For some buildings, it may be more practical to move to a modified replacement frame that accepts a more readily available filter format. our products can help with standard options, while custom manufacturing may be needed where the plant is unusual.

Access constraints can shape the filter choice

In many older office towers, access is the real limiter. Plantrooms may be tight, roof spaces may have limited clearance, and some filter banks can only be reached through narrow service doors or awkward walkways.

That matters because a filter that is technically suitable on paper may be impractical if it cannot be handled safely during changeover.

Consider:

• •whether the filter can be removed and installed by one person or requires a two-person lift
• •whether there is enough room for the filter to flex during removal
• •if service access requires shut-down planning or after-hours work
• •whether ladders, scissor lifts or confined access procedures are needed
• •how disposal of used filters will occur from the plant location

Where access is poor, it can help to select a filter format that is easier to handle, even if that means adjusting the maintenance approach. In some cases, a slightly different depth or frame style may make future servicing much easier.

If access problems are part of a broader maintenance issue, filter servicing or commercial filter servicing may be worth discussing with the building’s maintenance team.

Match filtration to the system and the site conditions

The best filter upgrade is one that balances air handling performance, available space and site conditions. Older towers often serve mixed tenancy types, which can create variable dust levels from lobby traffic, loading docks, carparks, kitchens or nearby construction.

A few points to keep in mind:

• •higher resistance is not automatically better
• •filters should suit the fan capability and the designed airflow path
• •finer filtration may require closer monitoring of pressure drop where gauges are fitted
• •the building’s maintenance records should inform what has worked previously and where issues have appeared

If a building is being upgraded to meet current ventilation expectations, AS 1668.2:2024 may be relevant, but site requirements should be confirmed with the mechanical services engineer or building owner. Older systems can have constraints that affect what is realistic to install without broader modifications.

Where washable products are being considered, remember that washability applies only to specific products. Check the product instructions before assuming a filter can be cleaned and reused.

Know the rating language before you specify

One common problem in older buildings is that different people use different rating systems in the same conversation. MERV, EN 779 and ISO 16890 do not convert directly, so it is best not to treat them as interchangeable.

That matters when a contractor is replacing legacy filters described as G3, G4 or F5 to F9. Those are EN 779 classes, which are now superseded by ISO 16890 but are still widely used in Australia. The label alone does not tell the full story of how a filter will behave in a particular system.

If a project requires HEPA filters, the specification should be clear. Under EN 1822, H13 filters are at least 99.95% efficient and H14 filters are at least 99.995% efficient at the most penetrating particle size. Those grades are only appropriate where the system is designed for them and where the housing, seals and fan performance support the application.

For many office towers, the correct answer is not to chase the highest available rating, but to select a filter that the system can actually use effectively and maintain consistently.

Plan for maintenance as part of the upgrade

Filter changes in older towers are easier when the maintenance plan is realistic. The right interval depends on the system, the site conditions and the dust load. It is best to follow the filter and equipment manufacturer instructions and to monitor pressure drop where gauges are fitted.

That approach is especially important where access is limited or the plant is non-standard. A building that is difficult to service can quickly become difficult to keep consistent if the filter choice ignores the practical realities of changeover.

A good maintenance plan should also note:

• •the exact filter type installed in each air handling unit
• •the frame or housing details for repeat ordering
• •any access instructions or permit requirements
• •whether seals, clamps or retaining systems need inspection at each changeover
• •any recurring issues with dust bypass, moisture or damaged frames

Keeping those details on file makes future replacements simpler and reduces the chance of ordering the wrong filter size or style again.

When you need a practical fit, not just a replacement

Older Queensland office towers often need more than a straight swap. They need filters that suit legacy plant, hard-to-source frames and difficult access conditions without creating extra work for the building team.

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, established 2009. If you need help matching an existing frame, specifying a replacement, or arranging filters for a complex plantroom, we can supply or make the right filters for the job.

Call 07 3800 3448 or request a quote. You can also view our products or contact us to discuss the requirements for your building.