Indoor Air Quality
Airflow & IAQ · Airflow & IAQ overview
Workplace indoor air quality (IAQ) describes the condition of the air people breathe inside a building — its pollutant content, freshness, temperature and humidity — and how that air interacts with the activities being carried out. Good IAQ is the product of adequate ventilation, controlled sources and a building operated the way it was designed.
What workplace indoor air quality means
Indoor air quality is not a single number. It is a set of related parameters — outdoor air supply per occupant, CO₂ as a ventilation marker, particulate concentration, volatile organic compounds (VOCs), humidity and temperature — that together describe whether occupants are breathing air that is fresh, clean and comfortable.
In UK workplaces, IAQ sits across COSHH, the Workplace (Health, Safety and Welfare) Regulations and HSE guidance on ventilation. The regulatory expectation is straightforward: enclosed workplaces should be ventilated with a sufficient quantity of fresh or purified air, and sources of contamination should be controlled.
Common IAQ concerns
IAQ issues turn up in commercial offices, laboratories, education buildings, healthcare premises and industrial spaces. The presenting symptoms vary, but the underlying causes are usually a small set of recurring problems.
- Stale air and stuffiness, often linked to under-ventilation and elevated CO₂.
- Persistent odours from photocopiers, kitchens, drainage, materials or neighbouring processes.
- Visible dust accumulation or particulate complaints near production or external intake points.
- VOCs from new furnishings, cleaning chemicals, solvents and stored materials.
- Comfort complaints — temperature swings, draughts, humidity extremes — that mask or worsen genuine air quality issues.
- Cross-contamination between zones because of pressure imbalance or transfer paths.
Ventilation, pollutants and occupancy together
IAQ depends on the balance between what is added to the air — by people, processes and materials — and what is removed by ventilation. CO₂ is widely used as a ventilation marker because it tracks occupancy and rises predictably when outdoor air supply is inadequate, but it is not itself the hazard in most workplaces. Treating CO₂ as the only IAQ metric overlooks particulates, VOCs and process contaminants that may matter more.
An honest IAQ review describes ventilation rate per occupant, pollutant sources within and outside the building, and the pathways by which air moves between zones. It avoids overclaiming on the basis of a single sensor reading.
How IAQ investigations are approached
A structured investigation starts with the complaint, then builds outward to the building. The assessor reviews ventilation drawings or current system condition, measures outdoor air supply against occupancy, samples key pollutants relevant to the activities present, and observes how air moves between contaminated and clean zones.
Findings are reported against recognised benchmarks where they exist — HSE workplace exposure limits, CIBSE TM40 guidance, BS EN 16798 indoor environment categories — and against the building's own design intent. Recommendations cover source control, ventilation adjustment, maintenance and, where appropriate, behavioural changes.
Relationship with ventilation and odour work
IAQ investigations very rarely sit on their own. Most IAQ problems trace back to under-performing ventilation, uncontrolled sources or unresolved odour pathways. A ventilation performance assessment usually accompanies any meaningful IAQ work, and odour complaints are often the entry point into a wider IAQ review.
Treating IAQ as a single discipline separated from ventilation engineering produces shallow recommendations. Treating it as part of the wider ventilation and exposure-control picture produces actions that actually fix the underlying problem.
Frequently asked questions
Is there a legal IAQ limit in UK workplaces?
There is no single statutory IAQ standard. Specific contaminants have workplace exposure limits under EH40, and the Workplace Regulations require sufficient fresh or purified air. Most organisations use HSE guidance, CIBSE TM40 and BS EN 16798 categories as practical benchmarks.
Does CO₂ monitoring alone tell us about air quality?
CO₂ is a useful marker for outdoor air supply relative to occupancy, but it does not measure particulates, VOCs or process contaminants. A complete IAQ picture combines CO₂ with sources, ventilation rate and any contaminants specific to the activities present.
Which buildings benefit most from IAQ investigation?
Offices and education buildings with comfort complaints, laboratories and industrial spaces with chemical or particulate sources, healthcare premises with infection-control requirements, and any building where ventilation has not been independently reviewed for several years.
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