The air inside: understanding indoor air quality

People often think about air quality as an outdoor issue, but the air inside homes, offices and other buildings matters too. Indoor air quality describes the condition of the air in enclosed spaces and the ways it may affect comfort and health.

Where indoor pollutants come from

Potential sources include cooking and heating, tobacco smoke, cleaning products, building materials, furnishings, dampness and outdoor pollution that enters through doors, windows or ventilation systems. The mix varies from one building to another, so there is no single explanation for every indoor air problem.

Three practical principles

Control the source. When possible, reduce or remove avoidable sources of pollution. Follow product instructions, store household chemicals safely and address moisture problems rather than masking their effects.

Ventilate appropriately. Bringing outdoor air inside can dilute some indoor pollutants. The useful approach depends on outdoor air conditions, the building and the activity taking place. When cooking, use an externally vented range hood if one is available and safe to operate.

Use filtration as a supporting measure. A correctly sized and maintained filter can reduce some airborne particles. Filtration does not remove every pollutant, and it does not replace source control or suitable ventilation.

Look at the whole room

Indoor air quality is not determined by one device or one habit. Heating, cooling, moisture, ventilation and daily activities interact. A filter may help with particles but will not solve a persistent leak; opening a window may help in some conditions but may be unhelpful when outdoor air is polluted.

For persistent dampness, unusual odours, symptoms that seem linked to a building or concerns about combustion appliances, seek qualified local advice. This article is general information, not a diagnosis or a building inspection.