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We spend most of our time indoors. Many people are not aware that the air inside buildings can be more polluted than the air outside.

Indoor air pollutants

Indoor air pollutants are found everywhere. It is obvious that tobacco smoke and candle smoke pollute the air. But pollutants are also hidden in building materials, furniture, sprays, cleaning products, etc. and are not always visible. Some are carcinogenic.

The most common pollutants are:


Formaldehyde is found in almost all buildings indoors and is present in some wood-based materials such as laminate flooring as well as vinyl wallpaper, insulating foams, adhesives, cleaning products, textiles, cosmetics, etc.

Volatile organic compounds (VOCs) in indoor areas

They already evaporate at room temperature. They are found in thinners, paints, varnishes and glazes, adhesives, etc. They are called benzene, toluene, styrene, xylene, etc. and can be recognized by their intensive smell.


They boil at more than 250 °C and evaporate for years. They are found in PVC coatings and furniture upholstery, among other things. They deposit fine dust particles.
PCB, polychlorinated biphenyls PCB makes plastics more elastic and is also used in varnishes and seals.


They are used in furniture, foams, insulation panels, textiles such as curtains, etc.

Nitrogen oxides and carbon monoxide

Nitrogen oxides and carbon monoxide are emitted by gas cookers.


For mould to grow indoors, the mould spores must come into contact with either moisture or cold walls. If water stagnates in these areas, mould is inevitable. If the moisture content of a material surface remains at 80 percent for several days, mould spores cause fungi to grow. Read also our article and video: How to avoid mould

How to improve indoor air quality

Ventilate regularly

Air well, i.e. air after cooking or showering, after extinguishing candles, but every day air the windows briefly but thoroughly 3 to 5 times a day, open as many windows as possible for a maximum of 5 to 10 minutes to create a draft. Good ventilation allows pollutants released by breathing and perspiration or by practical activities to be evacuated, prevents dust mites and moulds and humidity problems.

Check the temperature and humidity regularly. During the heating season, the ideal room temperature is between 20 and 21°C, and the ideal bedroom temperature is 18°C, with a relative humidity of 30-50%. If the air inside is too humid, ventilate immediately.

During the winter, prolonged ventilation with the windows ajar is a huge waste of energy. Hinged windows should not be left open all the time. It is therefore best to close the windows and skylights and ventilate briefly but thoroughly, 3 to 5 times a day. If you live in an energy-efficient house, set the ventilation correctly and change the filters regularly. Soft ventilation filters are easy to change. A maintenance contract can be concluded with a ventilation company.


Close the ventilation flaps of chimneys when not in use, but remember to open them before lighting the fire.


Plants are not only decorative, some plants can improve air quality and clean up pollution. They also have a positive impact on well-being, health and stress. A professional gardener can give you valuable advice on which plant is best suited to the environment (light, humidity).

Clean regularly

Clean, dust and vacuum regularly. Don't forget to clean ventilation and air outlets in bathrooms and to change filters regularly, for example the filter in the kitchen hood. If possible, use non-polluting cleaning products. 

There is no such thing as a pollutant-free interior, because they are everywhere. Nevertheless, it is possible to improve the indoor climate.


More information that may be of interest to you:

How to avoid mould
How to save energy (heating)


© Written by Esther Lauber, Real Estate Trustee with Advanced Federal Diploma of Professional Education and Training, real estate agent, property broker and manager in Carouge Geneva, translated with (free version)

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