A meeting room that feels stuffy by mid-morning, persistent odours in a retail unit, or repeated complaints of dry throats can point to an indoor environmental issue. But what does indoor air quality test for? The answer depends on the building, its activities and the concerns reported by occupants. A useful IAQ assessment measures selected airborne pollutants and environmental conditions, then considers the results alongside ventilation and HVAC operation.

For facility managers, the purpose is not simply to obtain a list of readings. It is to understand whether the air-handling system, occupied spaces and building activities may be contributing to poor comfort or air quality concerns – and what practical action should follow.

What does indoor air quality test for?

Indoor air quality testing can assess a combination of particles, gases, chemical contaminants and comfort conditions. It may also include a review of ventilation performance, air movement, filtration, housekeeping practices and potential pollution sources.

The scope should be planned around the building. An office with high occupancy may require close attention to ventilation and carbon dioxide trends. A manufacturing area may need testing that reflects its specific processes, materials and emissions. A kitchen, car park-adjacent space or recently renovated premises may present entirely different concerns.

Particulate matter and airborne dust

Particulate matter refers to very small solid or liquid particles suspended in the air. Testing may focus on PM10 and PM2.5, which are particle-size categories commonly used to understand fine dust levels.

Particles can enter from outdoor traffic, construction activity and haze, or originate indoors from dust accumulation, poor housekeeping, printing, cooking, combustion and certain work processes. HVAC systems can help manage particulate levels when filtration, ductwork and airflow are properly maintained, but they can also distribute accumulated dust when maintenance is neglected.

A particulate reading is a snapshot unless monitoring is carried out over a longer period. An assessor will therefore consider where and when measurements are taken, including occupancy, outdoor conditions and nearby activities.

Carbon dioxide and ventilation indicators

Carbon dioxide, or CO2, is often measured in occupied rooms as an indicator of how effectively outdoor air is being supplied relative to the number of people in the space. It is not normally the pollutant causing occupants to feel unwell at typical office concentrations. Instead, elevated CO2 can suggest that a room is overcrowded, poorly ventilated or not receiving the intended airflow.

This is particularly relevant in meeting rooms, classrooms, training rooms, call centres and enclosed offices. A one-off reading may be useful, but continuous monitoring through busy periods gives a more complete picture. Air balancing may be needed if certain zones receive too little supply air, even when the central system appears to be running normally.

Carbon monoxide and combustion-related gases

Carbon monoxide, or CO, may be included where fuel-burning equipment, vehicle exhaust or nearby loading areas could affect indoor spaces. Unlike CO2, carbon monoxide is a combustion by-product and requires prompt investigation if detected at concerning levels.

Potential sources include boilers, generators, kitchen equipment, smoking areas and vehicle fumes entering through doors, fresh-air intakes or leakage paths. Testing should be paired with a site inspection to identify the source rather than relying on a reading alone.

Volatile organic compounds and formaldehyde

Volatile organic compounds, known as VOCs, are gases released from a wide range of materials and products. Fresh paint, adhesives, carpets, furniture, cleaning products, solvents and renovation works can all contribute. Formaldehyde is one specific VOC that may be assessed where new furnishings, composite wood products or fit-out works are relevant.

VOCs can be difficult to interpret without context because the category covers many different chemicals. A total VOC result can indicate that further investigation is warranted, but it does not identify every compound or prove a particular source. Where odours or symptoms are linked to a known material or process, more targeted sampling may be appropriate.

Temperature, relative humidity and air movement

Comfort conditions are a core part of indoor environmental quality. An IAQ assessment commonly records temperature and relative humidity, and may assess air velocity or airflow patterns where needed.

A space can meet a basic temperature setting yet remain uncomfortable because air is not distributed evenly. Some occupants may experience cold draughts near diffusers while others sit in stagnant, warm areas. High humidity can also make a room feel warmer and may encourage condensation or mould growth where building surfaces are cool or damp. Very low humidity may contribute to dry eyes, throat irritation and static discomfort.

These findings often lead back to practical HVAC questions: Is the system correctly scheduled? Are filters clean? Are dampers operating? Is the fresh-air provision adequate? Has the layout changed since the air conditioning system was designed?

Biological contaminants and dampness concerns

Where there are visible stains, musty odours, water leaks or recurring mould, an assessment may include inspection for dampness and, where justified, microbial sampling. Possible biological concerns include mould spores, bacteria and allergens, although testing methods and interpretation need careful consideration.

Air sampling for mould is not a substitute for finding and correcting moisture problems. Spore levels can vary by time, weather and sampling location, while a hidden leak or contaminated material may not be captured by a short test. In many cases, a thorough inspection of ceilings, walls, insulation, drainage, condensate systems and air-conditioning components provides the most useful starting point.

What an IAQ test does not automatically tell you

An indoor air quality test is not a universal health diagnosis, nor can a single reading explain every complaint. Headaches, tiredness, eye irritation and odours can have several causes, including lighting, noise, workload, cleaning chemicals, humidity, poor airflow or conditions outside the building.

Likewise, a favourable test result does not mean maintenance can be ignored. Air quality changes with occupancy, weather, nearby construction, operating hours and the condition of HVAC equipment. The value of testing comes from combining measured data with site observations and a review of how the building is used.

Choosing the right scope for your building

A sensible assessment begins with clear questions. Are occupants reporting stuffiness at a particular time? Has a renovation recently been completed? Is there a musty smell after rain? Are complaints limited to one floor, one tenant area or one production zone?

From there, the assessor can select suitable parameters, sampling locations and times. For example, testing an empty meeting room early in the morning may miss the ventilation issue that appears when it is full. Measuring only one point in a large open-plan office may overlook poorly served perimeter areas. Industrial facilities may also require a more specific occupational hygiene approach based on the substances and processes involved.

Documentation matters. A useful report records the locations, timing, equipment used, site conditions, observations and limitations of the assessment. It should distinguish measured findings from likely causes that require further confirmation. This gives building managers a stronger basis for maintenance planning, contractor coordination and communication with occupants.

Turning test results into practical action

The next step may be as straightforward as replacing unsuitable filters, cleaning dirty grilles, correcting an air-conditioning schedule or improving fresh-air operation. Other findings may call for air balancing, duct inspection and cleaning, repair of a condensate drainage issue, source control during renovation works or a more detailed investigation.

Not every problem requires major system replacement. Equally, cleaning alone will not solve an issue caused by inadequate outside air, a faulty fan, water ingress or emissions from an indoor process. The right remedy depends on the evidence.

For commercial and industrial premises, Aircond Clinic can assess indoor environmental concerns alongside airflow, ductwork and HVAC conditions, helping teams focus on corrective work that fits the building. If occupants are raising repeated air-quality or comfort concerns, arranging an IAQ assessment is a practical first step towards a fresher, healthier indoor environment.