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86 SMT Magazine • March 2016 their separation efficiency is constantly high) and also in case of varying air flow (up to 98%). Further advantages are low maintenance and energy costs. Cartridge filters, however, are less flexible and require a higher investment. High-efficiency Submicron Particulate Filters Processes that apparently generate fewer pollutants are particularly critical, because low quantities of emissions in the nano range no longer effect an agglomeration, and nanopar- ticles keep their sizes (< 1 µm). These extremely fine particles enter the lungs and blood, and might in the worst case result in a shortened life expectancy. The utilisation of HEPA filters/ H-class filters (high-efficiency particulate air filters) is critical for ef- fective filtration. HEPA filters are used for air purification of up to 99.995%. They are pri- marily utilised as stor- age filters in the form of cassettes. In cleanroom technology, they are also used as plate filters or fan filter units (FFU), which means a combination of HEPA filters with con- trolled fan or prefilter. Ultra-low penetration air filters (ULPA) are applied if the air flow has to be nearly particle-free (de- gree of separation from 99.9995%). Modular Systems Airborne pollutants are usually a mixture of coarse and fine par- ticles—processes often produce particle sizes between >1 µm and <10 µm. In practice, extrac- tion and filtration sys- tems that combine the advantages of both fil- ter principles are well proven. Such units are specifically developed to meet special applica- tion requirements. Additional benefits are the availability of the equipment, price-related at- tractiveness as well as flexibility if application conditions change. adsorption of Gaseous air Pollutants Gaseous and vaporous substances can be stored in activated carbon or other sorbents. Ac- tivated carbon is made of organic materials (e.g., peat or nutshells) and provides an adsorption- capable surface of up to 1,700 m²/g. This means an extremely high degree of separation and an enormous storage capacity, which finally results in very high filter life. If particle concentrations are higher, combustion processes seem reason- fIltratIon tEChnology Figure 4: Principle cartridge filter system.