Air Filters for Floor-by-Floor AHUs in Multi-Tenancy Towers

In a multi-tenancy tower, separate air handling units serving individual office levels can create very different filtration needs from one floor to the next. The right filter choice depends on the air intake location, the tenant fit-out, occupancy patterns and the dust load each AHU actually sees.

For facility managers and mechanical contractors, the goal is to keep each unit operating as intended without overcomplicating maintenance. That starts with matching the filter to the system, then building a sensible inspection and replacement approach around real site conditions.

Why floor-by-floor AHUs need their own filter strategy

When each level has its own AHU, it is tempting to treat all of them the same. In practice, one unit may draw cleaner air from a sheltered façade while another sees more dust from traffic, loading docks, nearby construction or rooftop plant.

A floor-by-floor approach helps you:

• •match filter grade to the way each AHU is used
• •manage pressure drop and airflow more consistently
• •reduce the chance of one tenant level being maintained based on another floor’s conditions
• •simplify stock holding by identifying common sizes and formats across the building
• •plan access and service work around occupied spaces

This is especially useful in towers with mixed tenancy, where one floor may be mostly enclosed offices and another may have kitchens, print rooms or higher occupant turnover.

Start with the AHU, not the filter

Before choosing a replacement filter, confirm the filter frame size, depth, seal arrangement and how the filter sits in the AHU. Even small differences in size or gasket condition can affect bypass and maintenance effort.

Useful checks include:

• •the exact filter dimensions and holding frame type
• •whether the unit uses panel filters, pleated filters, bag filters or a combination stage
• •the available space for deeper or higher-capacity filters
• •whether there is differential pressure measurement fitted across the filter bank
• •the access path for removal and replacement, especially in plant rooms with limited clearance

If you are unsure about the dimensions, how to measure an air filter is a good place to start before ordering replacements.

It is also worth checking the equipment documentation and confirming site requirements with the mechanical services engineer or building owner. Where ventilation design requirements apply, AS 1668.2:2024 should be considered alongside the system design and tenancy conditions.

Choosing the right filter grade for different office levels

The right filter is not always the highest rated option. A higher resistance filter can be appropriate in some applications, but it must suit the fan capacity, the available filter area and the intended maintenance approach.

For multi-tenancy towers, consider the following:

• •General office floors: a well-selected pre-filter and final filter arrangement is often enough where the AHU serves standard office spaces with moderate dust loading.
• •Floors with higher particulate exposure: consider stronger upstream filtration where outdoor air intake conditions are harsher, or where nearby works increase dust load.
• •Floors with sensitive fit-outs: where tenants have specialist requirements, check whether the filtration stage needs to be tailored to the lease or fit-out brief.
• •Units with limited fan headroom: avoid specifying a filter that pushes the system beyond what the fan and controls can comfortably handle.

If a system is already in place, compare the installed filter type with the actual operating conditions before changing it. Sometimes the problem is not the filter grade itself, but poor sealing, restricted airflow, or a mismatch between the AHU and the tenancy layout.

For projects that need a non-standard size or construction, custom air filters can help when standard products do not suit the frame or service access.

Managing pressure drop across separate AHUs

Pressure drop is one of the most practical tools for managing filters in a tower. If gauges or sensors are fitted, monitor them so you can see how each AHU is performing over time rather than relying on guesswork.

A good maintenance routine should focus on:

• •recording the clean baseline pressure drop after installation
• •checking whether one floor’s filter bank loads faster than the others
• •looking for signs of bypass, poor seating or frame damage
• •replacing filters when the measured pressure drop and airflow performance indicate it is time, or as directed by the manufacturer instructions
• •confirming that replacement filters are installed correctly and seated evenly

Inspection frequency depends on the system, site conditions and dust load. A tower in a dense city environment may need closer attention than one in a sheltered commercial precinct, and the pattern can change during nearby construction or seasonal pollen events.

Make servicing practical for building operations

The best filter plan is one that technicians can actually carry out without disrupting tenants. In a multi-storey building, that means thinking about access, storage and consistency as much as product selection.

Practical steps include:

• •standardising filter sizes where the building design allows it
• •labelling each AHU clearly so the right filters go to the right floor
• •keeping a simple record of filter type, dimensions and installation date
• •checking whether some filters are designed to be washable, and only following the product instructions where that applies
• •using scheduled inspections alongside tenant complaints or visual checks, rather than waiting for airflow problems to become obvious

If your team handles ongoing maintenance across multiple sites, filter servicing and commercial filter servicing can support a more organised approach to replacement and record keeping.

Common mistakes in multi-tenancy towers

A few issues come up repeatedly in towers with floor-by-floor AHUs.

One common mistake is ordering filters by appearance rather than exact dimensions. Another is assuming all floors need the same media type, even though intake conditions and tenancy use can vary. It is also easy to overlook the effect of dirty frames, damaged seals or poorly seated filters, which can allow air to pass around the media instead of through it.

Other pitfalls include:

• •changing one floor’s filters but not reviewing the others
• •ignoring rising pressure drop until the system becomes difficult to balance
• •using a product that fits physically but is too restrictive for the unit
• •failing to confirm whether a finer final filter is actually needed for the application

If a building contains specialised areas alongside standard offices, look at the whole ventilation arrangement, not just the filter alone. In some situations, it may make sense to review the broader supply with the building owner or mechanical contractor so the filter specification aligns with the AHU and tenancy requirements.

Getting the right supply partner

For multi-tenancy towers, a good filter supplier should help you identify the right size, construction and format for each AHU, and assist with replacements when a standard option is not suitable. That matters when the building has many separate levels, multiple plant rooms or mixed service history.

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, established 2009. We can help supply the right filters for separate floor AHUs, including standard and custom options, and support your team with practical advice on fit and serviceability.

Call 07 3800 3448 to discuss your tower’s filter requirements or request a quote.

You can also view our products or contact us if you want help matching filters to a specific AHU or tenancy fit-out.