Why Indoor Air Quality in Office Buildings Starts with Your Ductwork

Most facilities teams reach for air purifiers or filter upgrades when complaints start coming in about stuffy meeting rooms or musty smells. While air purifiers and upgraded filters can help improve indoor air quality, they may not address the source of the problem if it lies within the ductwork. Leaks may allow conditioned air to escape into ceiling voids or draw contaminants into the system, affecting indoor air quality in office buildings. In Singapore, where air-conditioning systems run for long hours, even minor duct issues can have a noticeable impact. Understanding what is happening inside your ductwork can help you identify the source of poor air quality and decide when maintenance, sealing, or further inspection may be needed.

How Ductwork Affects Indoor Air Quality in Office Buildings

How Office Airflow Is Maintained

A commercial ACMV system is designed around a fairly precise airflow balance. A specified volume of supply air is intended to reach each zone, while return, exhaust and outdoor airflows are managed to maintain ventilation and building pressure. Ductwork is the delivery mechanism for that balance, running through ceiling voids, risers and plant rooms to connect the air handling unit to every diffuser on the floor. When it is intact, occupants get consistent temperatures and steady fresh air turnover without really noticing the system at work. The moment that delivery path develops gaps, the balance the designer calculated no longer matches what actually reaches the room.

Where Air Leakage Can Develop

Air duct leakage tends to build up gradually rather than appear all at once. Joints, flexible connectors, damper seals and riser penetrations are potential leakage points, particularly where seals deteriorate or connections are affected by thermal and pressure cycling. Older buildings and offices that have been through multiple fit-out cycles may also have ductwork that has been altered, extended or reconnected over time, creating additional areas that warrant inspection.

Why Air Filters Alone Are Not Enough

Upgrading filters addresses what passes through the coil, not what enters the system elsewhere. A leaking return duct can draw in air from ceiling voids, riser shafts or plant rooms before it ever reaches a filter. Although some particles may be captured by the filter, filtration cannot correct the unwanted airflow, humidity changes or pressure imbalances caused by the leak, nor can it remove every type of contaminant.

Indoor Air Quality Problems Caused by Leaky Ductwork

Problems with office duct work can affect indoor air quality in office buildings in several ways, from introducing contaminants to creating moisture and airflow issues.

Contaminants Entering from Unconditioned Spaces

Ceiling voids and service risers are rarely as clean as occupied office space. Dust, insulation fibres and construction debris can collect there over time. If air duct leakage occurs on the return side, air and contaminants from these spaces may be drawn into the HVAC system and circulated through occupied areas.

You may start to notice:

• More airborne dust and particulates
• Eye, nose or throat irritation
• Headaches, fatigue or general discomfort

Odours Spreading Between Office Areas

Leaks can also allow air to move along unintended paths. Odours from pantries, printer rooms or neighbouring spaces may travel through ceiling voids or other building pathways and enter different areas through the ventilation system.

Common signs include:

• Odours appearing away from their source
• Persistent smells despite regular cleaning
• Complaints concentrated in certain rooms or zones

Humidity Migration, Condensation and Mould

Singapore’s warm, humid climate makes moisture control particularly important. Supply duct leakage can reduce the cooled, dehumidified air reaching a space, while return-side leakage may draw in warmer, more humid air.

If that humid air reaches sufficiently cool surfaces, you may see:

• Condensation around ducts or ceilings
• Higher indoor humidity
• Conditions that support mould growth

Signs Your Office Ductwork May Be Affecting Air Quality

Facilities teams do not need a full audit to spot early warning signs. Problems with duct work can show up as recurring patterns across the floor, while also affecting overall indoor air quality in office buildings. Common signs include:

• Uneven airflow and stuffy office zones – some areas feel noticeably warmer, stuffier or less ventilated than others, and the imbalance persists even after thermostat adjustments.
• Recurring dust, musty odours and mould – dust settles faster than expected near diffusers, musty smells return after cleaning, or mould appears around ceiling or duct surfaces.
• Higher energy use – unexplained increases in HVAC energy use may occur when duct leakage causes the air distribution system to work less efficiently.

Any one of these could have another cause. When several appear in the same zone, the ductwork is worth inspecting alongside the ACMV equipment, filters and other possible causes.

Improving Ductwork for Healthier, Green Mark-Aligned Offices

Inspecting and Testing for Air Duct Leakage

Visual checks can only tell you so much. A lot of ductwork sits above ceilings or inside risers, so smaller leaks are easy to miss. Leakage testing gives facilities teams a clearer picture by pressurising the duct system and measuring how much air escapes at the test pressure. That gives you something more useful to work with than relying on comfort complaints or how a room happens to feel on the day.

Sealing Leaks and Restoring Balanced Airflow

Once the leaks are identified, sealing can help reduce air loss and bring airflow closer to what the system was designed to deliver. Traditional repairs usually require access to the affected joints, which can mean opening up ceiling sections when the ductwork is concealed.

For occupied offices, that can be disruptive. Aeroseal duct sealing takes a different approach by sealing leaks from inside the duct system. Using an aerosol-based technique, fine sealant particles are introduced into the pressurised ductwork, where they collect around leak edges and gradually seal the gaps. This reduces the need to access every joint manually, including areas that may be difficult to reach. This is the approach Delta Sirius uses for Aeroseal duct sealing in commercial buildings across Singapore.

Including Ductwork in Long-Term IAQ Management

Singapore’s SS 554:2026 Code of Practice for Indoor Air Quality in Air-Conditioned Buildings and the WSH Guidelines on Management of Indoor Air Quality in Air-Conditioned Workplaces both support a systematic approach to maintaining good IAQ. NEA’s current guidance also calls for regular ACMV maintenance, including checking air ducts and dampers for leakage or blockages.

The BCA Green Mark 2021 scheme places Health & Wellbeing alongside other building performance outcomes, with criteria covering areas such as ventilation, filtration and indoor air quality. For facilities teams, keeping ductwork in the maintenance programme therefore makes more sense than waiting until occupants start reporting problems.

Conclusion

Problems with indoor air quality in office buildings can sometimes be linked to a source teams overlook, the ductwork moving air around the building. Leakage is gradual, often invisible above the ceiling line, and its effects, uneven comfort, odour migration, humidity buildup and rising energy costs, tend to be misread as separate issues rather than one shared cause. Testing duct condition and sealing what is found is a more direct route to better office indoor air quality than another round of filter upgrades, and it supports Green Mark performance and workplace health compliance at the same time.

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