A meeting room that feels stuffy by mid-morning, recurring dust on workstations, lingering odours near a pantry, or repeated occupant complaints are useful warning signs. If you are asking, “how can I check my indoor air quality?”, start by treating those signs as evidence to investigate, not proof of one specific problem. Indoor air quality, or IAQ, is affected by people, outdoor air, cleaning activities, building materials, moisture and the performance of the air conditioning and ventilation system.

For building owners and facility managers, a good check combines occupant feedback, site inspection and measured data. This approach helps distinguish between a temporary issue, such as a crowded meeting, and an ongoing building condition that needs maintenance or corrective work.

How Can I Check My Indoor Air Quality Systematically?

Begin with a simple walkthrough of the occupied areas. Visit at different times of day, especially when complaints are most common. Note where the issue occurs, how long it has been present, whether it is limited to one floor or room, and whether it changes when the air conditioning system is operating.

Look for practical clues. Condensation around diffusers, water staining on ceilings, visible mould, dusty supply grilles, blocked return-air grilles and unusual odours all deserve attention. So do areas that are consistently too warm, too cold or noticeably more humid than surrounding spaces. These observations do not identify the contaminant on their own, but they help focus the investigation.

Speak to occupants as well. Ask whether symptoms or discomfort improve after leaving the building, whether a particular zone feels stale, and whether the concern occurs at a certain time. Keep the questions neutral. A headache or throat irritation can have many causes, so it should not automatically be attributed to the building air without supporting evidence.

Review maintenance records at the same time. Filter replacement dates, coil cleaning, drain pan condition, recent renovation works, pest-control treatments and changes to occupancy can all provide useful context. A newly partitioned office, for example, may have altered airflow distribution without the air conditioning system being rebalanced.

Measure the Conditions That Affect IAQ

Handheld and fixed IAQ monitors can provide useful information, provided they are correctly selected, maintained and interpreted. A low-cost monitor is often helpful for spotting patterns, but it should not be treated as a full building diagnosis. Sensor accuracy, calibration, placement and the time of measurement matter.

The most relevant parameters depend on the building and the complaint. In a typical commercial premises, an assessment may consider:

• Carbon dioxide (CO2): This is commonly used as an indicator of occupancy and ventilation adequacy. It is not a complete measure of air quality, but rising readings in a busy room can suggest that fresh-air supply is not keeping pace with occupancy.
• Temperature and relative humidity: These affect comfort and can contribute to condensation or mould risk. In Malaysia’s humid climate, controlling moisture is particularly important. Relative humidity should be assessed alongside air conditioning operation, building use and signs of moisture, rather than as an isolated reading.
• Particulate matter: Fine particles can enter from outdoors or be generated indoors by activities such as renovation, printing, cooking or poor housekeeping. Particle readings are especially relevant near loading areas, busy roads, workshops and kitchen zones.
• Volatile organic compounds (VOCs): VOCs may be released from paints, adhesives, furnishings, cleaning products and stored chemicals. A total VOC reading can indicate a need for further investigation, but it does not identify every individual chemical.
• Carbon monoxide: This is particularly important where combustion appliances, vehicle exhaust, generators or enclosed loading areas may affect occupied spaces. Carbon monoxide concerns require prompt attention because the gas is colourless and odourless.
• Airflow and pressure relationships: Air quality depends on how air moves through a building. Insufficient supply air, weak extraction, short-circuiting between supply and return grilles, or the wrong pressure relationship between spaces can spread odours and contaminants.

Measurements should be taken in representative occupied locations, away from direct supply air, open windows, doors and obvious local sources unless those sources are being investigated. Comparing readings across several areas and over time is more meaningful than relying on one spot check.

Check the HVAC System Behind the Readings

An IAQ monitor can show that a condition exists, but it cannot always explain why. That is where the HVAC system needs closer attention.

Inspect air handling units, fan coil units, filters, cooling coils, condensate drains, outdoor-air intakes and ductwork where access is available. Dirty filters may restrict airflow, while a dirty coil can affect cooling and moisture removal. A poorly maintained drain pan or blocked condensate line can create persistent moisture conditions. Damaged insulation, unsealed duct joints or accumulated dust in ducts may also contribute to comfort or cleanliness concerns.

Check whether outside-air intakes are clear and appropriately located. An intake positioned near vehicle exhaust, kitchen discharge, smoking areas or waste-handling zones may draw unwanted pollutants into the system. Likewise, an exhaust fan that is not operating effectively can allow odours and humid air to remain indoors.

Air balancing is another important part of the picture. A system may be running, yet still deliver too much air to one area and too little to another. In offices, retail spaces, classrooms and industrial facilities, this can create localised stuffiness, temperature differences and complaints that routine servicing alone does not resolve.

When a Professional IAQ Assessment Is the Better Choice

A basic inspection and portable monitor are sensible first steps for a small, straightforward concern. However, professional assessment is advisable when complaints persist, mould or water damage is visible, odours cannot be traced, work has recently been carried out, or the building has sensitive occupants or higher-risk activities.

A structured IAQ assessment normally begins with a site review and an understanding of the building’s use, occupancy and HVAC arrangement. The assessor can then develop a measurement plan suited to the concern. This may include real-time monitoring, airflow checks, ventilation review, moisture investigation and targeted sampling where justified.

The purpose is not simply to produce readings. It is to interpret the findings in context and identify proportionate actions. For example, elevated particles near a renovation zone may call for better containment, cleaning and filtration. Stale air in a meeting room may point to occupancy patterns, inadequate outdoor-air provision or airflow imbalance. A musty smell near a fan coil unit may require inspection of drainage, coil condition and nearby building fabric.

Be cautious of anyone who promises that one test can certify an entire building as healthy. Indoor air quality changes with weather, occupancy, activities and system operation. A credible assessment explains what was measured, when and where it was measured, the limitations of the data, and what should happen next.

Turn Findings Into a Maintenance Plan

Once you understand the likely causes, prioritise actions that reduce the source of the problem and improve control. Removing a moisture source is more effective than masking a musty smell. Improving ventilation and airflow is usually more useful than relying only on air fresheners. Filter upgrades may help with particles, but they must be compatible with the system and installed without creating excessive pressure drop.

For many commercial buildings, the practical plan may include scheduled filter checks, coil and drain maintenance, periodic inspection of outdoor-air intakes, cleaning of accessible grilles, and review of airflow after layout changes. Duct cleaning should be based on inspection findings and building conditions, not performed as a substitute for correcting moisture, filtration or ventilation faults. Where dust and debris have accumulated within ductwork, robotic duct inspection and cleaning can provide documented evidence of the condition and support targeted maintenance.

Keep a simple record of complaints, monitoring results, maintenance work and any changes made. Over time, this helps property teams identify recurring issues and make better decisions about repair, cleaning or system upgrades.

Fresh indoor air is not created by a single device or one-off reading. It comes from a building that is inspected carefully, ventilated appropriately and maintained with evidence in mind. When the cause is unclear, an independent IAQ assessment can give your team the information needed to act with confidence. Aircond Clinic can support that process with practical indoor air quality, airflow and HVAC maintenance services designed around the conditions in your building.