Cabin ventilation filters

Vehicle cabin ventilation filters are designed to supply fresh filtered air into the passenger compartment through the automotive heating and air conditioning, or interior air recirculation systans. These filters can be more than 90% efficient and, where electrically charge fibres made from 100% polypropylene are used as the filter medium, so... 

The need for proper ventilation of vehicle cabins, whether an agricultural tractor, a private car or a passenger airplane, has been recognized only comparatively recently. This means that air intake (or recirculation) filters are not only required, but also must be able to remove airborne dust, pollen and microbes very efficiently. 

However, in the 90s, ironically with more evolved technology, ventilation systems in aircraft were built in such a way as to recycle stale air, thus increasing the chances of survival of bacteria and deleterious particles in the aircraft cabin. Even if such a practice were ineluctable, in that recycling is a universal practice which is calculated to conserve fuel, a prudent airline would lake other measures, such as change of air filters through which ventilation is provided. 

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