Indoor air quality in offices: HVAC fixes that help

Staff complaining of stuffy meeting rooms, lingering odours, or hot and cold spots is usually a clear sign that your indoor air quality (IAQ) needs attention. These problems not only affect comfort but can also reduce productivity and overall satisfaction in the workplace. Most of these issues trace back to how your heating, ventilation, and air conditioning (HVAC) systems are installed, maintained, and controlled. For example, poor ventilation rates can cause stale air and build-up of odours, while dirty filters and coils restrict airflow and reduce system efficiency.

Incorrect balancing of air distribution can create uneven temperatures, resulting in hot or cold spots. Regular maintenance and proper control settings are essential to keep your HVAC system running smoothly and ensure a healthy, comfortable office environment.

Typical indoor air quality complaints in offices

Office IAQ problems rarely appear out of nowhere. They tend to build up over time as filters clog, controls drift from the original design and occupancy patterns change.

Facilities and office managers often hear similar comments from staff, including:

• Stale or stuffy air in meeting rooms or open-plan areas

• Persistent odours from kitchens, toilets or printers

• High humidity or condensation on windows and cold surfaces

• Dust build-up on desks, vents and IT equipment

• Hot and cold spots despite the thermostat being set correctly

On their own, these issues can seem minor. Together, they point to an HVAC system that is not quite delivering the clean, well-controlled air it was designed to provide.

How HVAC problems affect indoor air quality

HVAC equipment is at the heart of office IAQ. When it is maintained and controlled properly, it can dilute pollutants, manage humidity and keep temperatures stable throughout the day.

When it is not, a few common issues tend to appear.

Poor ventilation and stale air

If staff complain that rooms feel sleepy or heavy after a meeting, the outside air rate may be too low. Mechanical ventilation systems are designed to bring in fresh air and exhaust stale indoor air, but dampers can stick, and control setpoints can be changed over time.

In some cases, energy-saving adjustments reduce fresh air too much, especially in boardrooms and densely occupied open-plan spaces. The result is rising CO2 levels, stuffiness and lingering odours.

Dirty filters, coils and dust complaints

Air filters are your first line of defence against dust and debris. Once they clog, they can restrict airflow and allow particles to bypass the filter housing. This is often when you see dust on diffusers, grilles and ceiling tiles.

Dirty evaporator or cooling coils also affect IAQ. Reduced heat transfer can leave air warmer and more humid than intended, making the space feel muggy even if the thermostat looks fine.

Humidity issues and blocked condensate drains

High humidity and condensation on windows are often linked to cooling equipment not draining condensate correctly. Blocked or poorly trapped condensate drains can cause water to pool in fan coil or air handling units.

This can create damp patches, water staining and, in the worst cases, odours from stagnant water. It also reduces how effectively the system dehumidifies the air.

Balancing, controls and hot/cold spots

Uneven temperatures and drafts usually indicate balancing or control issues. Over time, layout changes, new partitions and extra IT equipment can all throw the original design out of balance.

If supply and return grilles are poorly located or have been blocked by furniture, individual zones may struggle to reach setpoint. Incorrect time schedules or sensor locations can also mean the system runs at the wrong output for actual occupancy.

IAQ quick audit for facilities teams

You do not always need tools or invasive inspections to get a first picture of IAQ performance. A simple visual and behavioural audit can highlight where a maintenance visit will have the most impact.

Simple visual checks you can carry out safely

Walk your offices and light-commercial areas with IAQ in mind. Look and listen for anything that suggests air is not moving or being treated correctly.

• Filters: Check any accessible fan coil or split units for filter access panels. If safe to do so, open and look for dark, visibly clogged filters.

• Grilles and diffusers: Note any visible dust build-up around supply or extract grilles, especially dark streaks on ceilings.

• Water staining: Look above ceiling tiles under fan coil units for staining, and around unit casings for signs of leaks.

• Condensation: Record where windows regularly mist up or show mould staining to the frames or sills.

• Noise and airflow: Listen for unusually quiet fans that may not be running when they should, or very noisy ones that may be failing.

Keep notes of locations, the time of day and what the space was being used for. This helps your HVAC contractor link symptoms to causes when they attend.

Using CO2 monitoring in offices

If your building has CO2 monitors, they can be a useful indicator of how well a space is ventilated. Higher CO2 levels generally mean that the air is being recirculated faster than fresh air is being introduced.

Look for patterns rather than single readings. Meeting rooms that regularly show elevated levels during normal use are candidates for increased fresh air, extended purge times or occupancy-based controls.

HVAC maintenance routines that support good IAQ

Once you have a basic picture of where the issues lie, routine maintenance and targeted upgrades can steadily improve IAQ. The focus is on keeping air moving as designed, filters effective and moisture well controlled.

Regular filter changes and cleaning

Set up a clear schedule for checking and replacing filters in air handling units, fan coils and split systems. Do not rely on time alone; ask your contractor to base intervals on operating hours and local conditions.

Correctly fitted filters, with suitable ratings for office use, reduce dust and help keep internal components clean. This in turn supports both air quality and energy performance.

Coil cleaning, condensate care and humidity control

Periodic cleaning of evaporator and condenser coils helps your systems maintain design temperatures and humidity levels. Cleaner coils also reduce the risk of odours from biofilm build-up.

During maintenance visits, ensure condensate trays and drains are checked, cleaned and proven to run freely. This simple step goes a long way to avoiding water staining, damp odours and moisture issues around units.

Ventilation rates, balancing and controls

A review of your fresh air rates, especially in meeting rooms and busy open-plan areas, can significantly improve perceived air quality. Your contractor can check damper positions, fan operation and control strategies against occupancy patterns.

Rebalancing supply and extract systems, including simple grille adjustments, helps smooth out hot and cold spots. Updating control schedules so that ventilation starts before occupancy and runs on after peak use will also support better IAQ.