Today already, filter systems in the climate control systems of buses from Setra remove particles from the air. New active filters increase this effect even further: the multi-layer, progressively designed high-performance particle filters additionally feature an anti-viral functional layer. This serves to filter out the finest aerosols. Physical tests and microbiological analyses confirm this effect. The active filters are used for the roof-mounted climate control systems, for the air-recirculation filter and also for the front climate control box. Since mid-August, these have been available for order, both for new vehicles and as a retrofit solution. At the end of August, the S 531 DT double-decker will follow suit, as will the S 431 DT predecessor model and, from September, further TopClass 500 models too. From the stated date, Setra will be able to fit these in new vehicles and in models which are already on the market. Vehicles equipped with an active filter are also fitted with a sticker in the entrance area which is visible to passengers.