Air purification

If it is not possible to achieve hygienically acceptable indoor air quality either through a targeted selection of building products and furnishings or through controlled ventilation behavior, it may be necessary to take additional measures to reduce (temporarily) increased concentrations of air pollutants.

Room air purifier

One option is to install a room air purifier. These work with different techniques such as photocatalysis, electrostatic precipitators, plasma, UV, ozonization or various adsorption filter techniques. The latter require regular filter replacement. Most devices do not affect the CO₂ levels or the humidity balance, which may require additional measures. When operating an air purifier, in addition to the "decomposition products" carbon dioxide and water, other substances may be formed which are released back into the room air. Formaldehyde is one of these typical compounds. Technically advanced air purifiers can certainly be suitable for reducing air pollutants or odorous substances in the room air, but they are more of a supplementary measure.

Fuctionalized surfaces

The degradation of unwanted air pollutants or odorous substances can also take place via so-called functionalized surfaces. Such surfaces (e.g. wall paints, textiles, etc.) adsorb air pollutants and break them down with the help of a catalyst. Ideally, the air pollutants are "mineralized" into carbon dioxide and water.

However, degradation reactions work under laboratory conditions often face limitations in real-world conditions. For example, photocatalysts require light with sufficient intensity and a suitable wavelength. Additionally, the contact time of the substance to be degraded on the surface must be sufficiently long. As these requirements are often insufficiently met in practice, incomplete degradation reactions can occur, resulting in substances that can "poison" the catalyst, have unpleasant odors, or even be harmful to health. Furthermore, self-decomposition has been observed in some products, which can lead to the formation of formaldehyde, for example.

Therefore, only products that have proven their indoor compatibility under realistic test conditions should be selected for use.

• Gunschera, J., et al., 2009. Surface-catalysed reactions on pollutant-removing building products for indoor use. Chemosphere 75, 476-482.
• Gunschera, J., et al., 2016. Portable photocatalytic air cleaners: efficiencies and by-product generation. Environmental Science and Pollution Research 23(8), 7482-7493.