Filtrera
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A Medium with a Future

Filters for ventilation systems in residential buildings and industry are a frequently underestimated part of everyday life. But their impact should not be disregarded: they not only support the ongoing implementation of hygienic measures to contain the novel coronavirus, but they are generally of value whenever the aim is to make indoor air healthier for people. And while they may sound simple from the outside, the inside actually houses a complex structure.

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The market for filters and filter media is currently showing strong signs of growth. And it’s not just modern residential buildings with high energy efficiency requirements that have a role to play here; the desire for reliable filtration solutions against the new coronavirus is also increasing demand. More and more products are appearing in the electrical trade sector, including for private use, which are supposed to rid the indoor air of harmful influences. There are a number of differences between the various models, too: while some manufacturers rely on simple filter media made of paper, other models from high-quality brands contain complex filter elements. These combination filters consist of materials such as activated charcoal medium and nanofleeces. In any case, the production of filters is an intricate affair – and the adhesive used has to fulfil a multitude of other tasks in addition to the bond. Building filters for treating indoor air bind together minute particles such as fine dust, pollen or smoke particles. But pathogens such as bacteria or viruses can also be removed from the air with the help of filters, which is why building filters have become relevant for combating the novel coronavirus. Manufacturers such as Freudenberg Filtration Technologies offer filter media that can help to reduce the virus load in indoor air and thus minimise the risk of infection.

A multi-layered medium

The HEPA filters used for the filtration of building air are known as depth filters. These are divided into the filter classes EPA (Efficient Particulate Air), HEPA (High-Efficiency Particulate Air) and ULPA (Ultra-Low Penetration Air). They keep indoor air clean and thus ensure healthy air in environments such as offices and production halls. Synthetic materials like glass fibre fleece are used as the basis for depth filters. Additional lamination with further filter media may be required to achieve improved product properties such as higher stability or increased filtration efficiency. For optimum filter performance, the largest possible surface area is needed in a small space, as Jowat product manager Michael Dressler explains: “The filter medium is pleated for this purpose and fixed with a hot melt adhesive. This maximises the filter area within the available space.” Adhesives such as Jowatherm® 262.30 based on ethylene vinyl acetate (EVA) are optimally adapted to the pleating process with a suitable open time as well as high initial strength. In addition, the hot melt adhesives are strong when cooled down, while also being flexible enough to allow for safe handling of the filter elements. For easy installation and replacement of the filter media in the ventilation systems, they are fitted with frames made of wood, metal or plastic.

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