The units are designed for decontamination and fine filtration of air in rooms of all cleanroom classes including especially clean rooms and infectious environments. A standalone units does not need a connection to the existing ventilation and air conditioning systems and allows a local "clean" zone to be created in any room. The appliance can be used either as a standalone unit to create local sterile zones or in conjunction with other sanitary and hygienic measures taken when preparing the room for use.