Air-purifying. Pollutants and odours are broken down into their constituent parts. Does not replace ventilation, but improves air quality.

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1 Air-purifying AIR-PURIFYING Pollutants and odours are broken down into their constituent parts. Does not replace ventilation, but improves air quality. Though not able to completely purify air, the use of nanomaterials nriakes it possible to improve the quality of air. It enables unpleasant odours and pollutants to be eradicated. Healthy air is a fundamental and ever more important resource that at the same time is becoming ever more precious. Legislation was initially introduced to reduce the level of outdoor air pollution; the need to improve indoor air quality followed later. The air-purifying properties of nanomaterials are beneficial in both cases and play an important role both for indoor as well as increasingly for outdoor environments. Indoors The indoor air quality is particularly important in industrialised nations where people spend a large amount of time indoors and unpleasant smells or even pollutants are commonly associated problems. Although our sense of smell greatly influences our general feeling of well-being, it is all too often neglected. Together with hazardous substances, unpleasant smells have a significant effect on how we feel. Even the most beautiful space will not feel comfortable if the indoor air quality is disagreeable. We usually deal with this problem by more or less eliminating any unpleasant smells indoors, either by airing the room, by masking it with another perfume or with the help of resorptive materials, though these have a limited capacity. Nanotechnology, on the other hand, makes it possible to chemically decompose odours into their harmless constituent parts. Here the molecules are cracked, giving off steam and carbon dioxide.

2 Air-purifying curtain materials can simultaneously be equipped with antibacterial properties. Various products are already available on the market, with or without antibacterial combination.

3 This approach can also be used to counteract the sick building syndrome (SBS). To function adequately, the air-purifying surface area must be sufficient with regard to the volume of the room. Only surfaces that are exposed to the air, i.e. those not concealed by furniture, are relevant. For processes based on oxidative catalysis, normal air circulation is sufficient, however photocatalytic processes, which can also be used for air-purifying purposes, require daylight. As such the use of photocatalytic systems indoors must be planned carefully. A further advantage is that the catalytic effect and therefore the purifying function of nanomaterials does not wear off. The same principle applies for pollutants such as nicotine or formaldehyde. Their molecules can also be cracked and filtered out of the indoor air In contrast to other well-known pollutants such as asbestos, formaldehyde is not always pre-existent in a building but can be introduced as part of new installations. The ability to reduce indoor air pollutants is therefore equally relevant for new as well as for existing buildings to avoid the occurrence of sick building syndrome. Nicotine is a further substance that can be broken down using nanomaterials, and can in some cases obviate the need for separate smoking and non-smoking areas. Ammonia, benzene and fish odours are among further contaminants that can be removed with the help of nanomaterials, and the palette is expanding constantly as research into the decomposition of further substances continues. Air purification technology is increasingly being used for textiles and paints. It should be noted that although it is possible to improve the quality of air, this does not necessarily make it "good". Other factors such as oxygen content and relative humidity also contribute to the air quality and should not be neglected when using airpurifying products. It would be wrong to assume that an air-purifying carpet means one no longer needs to open the window - it cannot replace regular ventilation. Insufficient ventilation leads to an inevitable build-up

4 Air-purifying curtains across the width of this dance and work-out room help maintain a better indoor air quality. Air-purifying interior plaster. In the call centre of "die fabrik" in Cottbus, Germany, the surfaces are both air-purifying and sound insulating. The European headquarters of Hyundai Motors Europe in Offenbach, Germany, Is lined with air-purifying plasterboard panels - an interesting combination for a car manufacturer. Air-purifying materials such as plasterboard or acoustic panels. Air-purifying

5 of relative humidity and eventually results in mould formation and further associated problems. The oxygen content of air is a further contributory factor for indoor air quality Lastly, a third good reason to ventilate sufficiently is to allow the CO2 that is generated to escape. Our sense of smell also serves as a warning and by eradicating the smell of something, for instance urine, we trick it but without removing the cause. The same applies for apparently nicotine-free spaces - other pollutants from cigarette smoke are still present in the air. Rather than just dealing with the symptoms, spaces should be properly cared for. It is always better to remove the cause than to tackle the bad air. However, where this is difficult, or impossible to influence, airpurifying surfaces can help improve the indoor air quality and with it the comfort of the users. It is not an all-encompassing solution for dealing with indoor pollutants. Outdoors Environmental pollution and the quality of air outdoors has long been a topic of public discussion in Europe, particularly as public education and awareness of ecological aspects and sustainable development increases. More and more companies are demonstratively highlighting their commitment to sustainability and the eco-movement has emancipated itself from its previous niche existence to a marketing and lifestyle factor. The air-purifying capacity of photocatalytic concrete for example provides a possible means of combating existing pollutants. Recently, building fagades, road surfaces and the like, equipped with appropriate coatings, are being implemented in test installations to counteract the effect of industrial and vehicle exhausts. It transpires that photocatalytic self-cleaning concrete (see p. 117) for example also has an additional air-purifying effect. This added effect was discovered only later and new developments are regularly making press headlines. Applications are air-purifying paving stones, road surfaces and paints. At present these materials are still expensive, but a start has been made. Noteworthy in this respect is the "Picada" research project - Photocatalytic Innovative Coverings Applications for Depollution Assessment - funded by the EU from 1996 to As part of the project, test installations and pilot projects were undertaken to demonstrate the

6 Photocatalytic pavement surfacing. Concrete paving panels with photocatalytic properties used as a design element in a car park. efficiency of photocatalytic air-purifying surfaces. Depending on the respective conditions, it was possible to eradicate between 20% and 80% of airborne pollutants. Pedestrians walking in the vicinity of treated walls breathed in fewer airborne pollutants. As with indoor air environments, outdoor air purification applications are only a supporting measure for tackling symptoms and are an adequate means of reducing existing pollution. They do not eradicate the cause of pollution but can be used to reduce smog and improve the outdoor air quality. The question is whether a noticeable difference to the quality of air can be made with the use of air-purifying surfaces, and how significant this effect actually is. With regard to reducing air pollutants, greater attention should be given to avoiding their emission in the first place. However, it will take a while before environmental protection aims are fully realised. Until then, once their effectiveness has been demonstrated, airpurifying surfaces may offer a possible interim solution. It remains to be seen wheter one day the extensive use of such surfaces will become standard practice in urban conurbations. Air-purifying