Managing Construction Dust During an Office Refurbishment Without Damaging AHUs

Office refurbishments can keep a building operating while walls come down, partitions move and new finishes go in, but that mix of demolition, plastering and joinery also creates a difficult dust environment for HVAC systems. If construction dust reaches the air handling units, it can load filters quickly, foul coils and disrupt the balance of floor-by-floor systems.

The aim is not to stop every particle at source forever. It is to manage the work so the building stays serviceable, the AHUs are protected, and the filtration arrangement can keep doing its job while the project moves through each stage.

Why construction dust is a different risk in occupied buildings

Construction dust behaves differently from everyday office dust. It can be finer, heavier in volume and more variable from day to day, especially when sanding plaster, cutting board, trimming joinery or breaking out old finishes. Once it gets into return air paths, it can travel well beyond the work zone.

In an occupied building, that creates a few common problems:

• •Filters can load faster than expected, increasing resistance across the system.
• •Dust can bypass poorly sealed filter frames or access doors.
• •Fine material can settle on fan components, heat exchange surfaces and ductwork.
• •Floor-by-floor systems may be affected unevenly, with one level seeing more dust than another.
• •Temporary isolation measures can be compromised by doors being propped open or penetrations left unsealed.

This is why the filtration plan should be considered alongside the demolition and fit-out sequence, not after the dust has already spread.

Start with a clear protection plan before demolition begins

A practical dust control plan should be agreed before the first walls come down. For occupied refurbishments, the mechanical services engineer, building owner and contractor should decide how the system will operate during each stage, including which areas remain live, which AHUs are serving which floors, and where temporary isolation is needed.

For ventilation and air-conditioning arrangements, it is sensible to check site requirements against AS 1668.2:2024 and the building’s own operating rules. The exact approach will depend on the system layout, the work scope and the condition of the existing plant.

Useful items to confirm early include:

• •Which AHUs or air handling zones serve the refurbishment area.
• •Whether the system can be partly shut down, staged, or run at reduced coverage during dusty tasks.
• •How return air paths will be sealed or separated from the work area.
• •Whether temporary filtration is needed at entry points, hoardings or negative pressure zones.
• •Who is responsible for inspection of filters, pressure gauges and access panels.

If the project uses replacement filters or custom sizes, it is worth measuring the existing filters accurately before ordering. Our guide on how to measure an air filter can help avoid errors when you are replacing filter banks or checking legacy frames.

Protect the AHUs as work progresses

The biggest risk to an AHU during refurbishment is usually not a single dramatic event. It is ongoing dust migration through open gaps, return air paths and unsealed penetrations. Once dust reaches the unit, the filter bank becomes the first line of defence, but it can only do so much if it is overloaded or fitted poorly.

Keep dust out of the return air path

Where possible, physically separate the work zone from the conditioned space. That may involve sealed hoardings, taped joints, sealed service penetrations and managed access points. If workers need to move materials through occupied areas, set up routes that do not pass directly through return air grilles or plant access points.

Protect the filter bank and housing

Check that the filter frame is sound, the gaskets seat properly and the access door closes securely. Even a good filter will struggle if air can bypass around the edges. If there are signs of damage, corrosion or poor fit, arrange repairs before the most dusty work begins.

For many occupied sites, the best approach is to confirm the current filter grade and the condition of the holding frame, then decide whether a temporary upgrade or additional stage of filtration is needed for the construction period. If you need support with standard or custom dimensions, see our products or custom air filters.

Monitor pressure drop where gauges are fitted

Pressure drop is one of the most useful indicators during a refurbishment. If gauges are fitted, watch for rising resistance as dust loads the filter bank. That does not by itself tell you to replace a filter on a fixed schedule, because inspection frequency depends on the system, the site conditions and the dust load. Follow the equipment and filter manufacturer instructions, and assess the condition of the filters in context.

Choose filtration that suits the work stage

Not every phase of a refurbishment needs the same filter arrangement. Demolition, plastering and joinery each create different dust characteristics, so the filtration strategy may need to change as the job moves forward.

For example, the system may need stronger pre-filtration during breakout work, then closer inspection and replacement after sanding and trimming begin. In some sites, temporary filters can be fitted to protect the main bank while the heavy dust phase is underway. In others, the best approach may be staged shut-downs, localised extraction and careful sealing rather than relying on a single filter upgrade.

Where higher-efficiency filters are being considered, make sure the selection suits the fan capability and the system design. Filter ratings from different standards do not convert directly, so a MERV rating should not be treated as equivalent to an EN or ISO class without checking the actual product data. Older EN 779 classes such as G3, G4 and F5 to F9 are still widely used in Australia, even though the standard has been superseded by ISO 16890.

If the project involves portable units or specialist filtration, some filters are designed to be washable - check the product instructions before reusing anything. Do not assume that a filter can be cleaned unless the manufacturer says so.

Control the dust source as well as the air system

Good filtration helps, but source control is still essential. The cleaner the work zone, the less dust reaches the AHUs and occupied areas.

Practical site controls include:

• •Using local extraction for cutting, sanding and drilling where possible.
• •Keeping materials covered when stored or moved through the building.
• •Dampening fine dust at source where the task allows it.
• •Cleaning surfaces with suitable methods rather than dry sweeping.
• •Managing access so doors are not left open to pressurised or filtered areas.
• •Removing waste regularly so debris does not continue to shed dust.

It is also worth checking whether the building’s controls are creating the right pressure relationships between the refurbishment area and the rest of the site. A poorly managed pressure regime can push dust into clean areas faster than filters can remove it.

Inspection and replacement should follow site conditions, not a calendar

There is no single replacement timetable that suits every refurbishment. A lightly occupied office with minor joinery work will behave differently from a full-floor demolition with plaster sanding and repeated material movement.

Instead of relying on a fixed schedule, inspect the system based on how the work is progressing and how the filters are performing. Look for visible loading, damage, bypass, poor sealing and pressure rise. Keep a record of what was found, what was changed and when the condition was checked, especially if multiple contractors are using the same plant room.

If the existing filters are damaged, not sealing properly, or no longer suit the temporary conditions, replacement may be the most practical option. In some cases, a custom size may be needed to match older AHU frames or non-standard filter banks. That is where proper measurement and specification matter. If you are unsure, contact the filter supplier before ordering so the replacement suits the frame and system.

Keep the building team, contractor and supplier aligned

The cleanest refurbishment outcomes usually come from clear communication between the contractor, the building manager and the mechanical services team. Everyone should know when dusty work is starting, what areas are isolated, and when the filters or plant need inspection.

For facility managers and industrial buyers, the main priorities are simple: protect the AHUs, keep air moving where it should, and make sure the filter arrangement matches the actual site conditions. If a change in scope means the existing filtration is no longer suitable, act early rather than waiting for the system to strain under the load.

Need the right filters for a live refurbishment?

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, and we can help supply or make the right filters for your project, including standard and custom sizes. Call 07 3800 3448 or request a quote, and if you need help choosing replacements or organising ongoing care, see commercial filter servicing or contact us.