The decontamination device, comprises a space (3) to be decontaminated such as insulator space, a cleaning device (7) for removing gaseous- and/or vaporous decontaminant such as hydrogen peroxide from indoor air, a device (16) comprising a vaporizer (23) for supplying the decontaminant, an exhaust outlet for discharging excess decontaminant during a conditioning phase, and a device for conditioning and supplying fresh air. The cleaning device is arranged in such a way that the indoor air is circulated through the cleaning device by a blower (5). The decontamination device, comprises a space (3) to be decontaminated such as insulator space, a cleaning device (7) for removing gaseous- and/or vaporous decontaminant such as hydrogen peroxide from indoor air, a device (16) comprising a vaporizer (23) for supplying the decontaminant, an exhaust outlet for discharging excess decontaminant during a conditioning phase, and a device for conditioning and supplying fresh air. The cleaning device is arranged in such a way that the indoor air is circulated through the cleaning device by a blower (5). The cleaning device comprises a catalyst for chemical splitting of the decontaminant, and open-porous metal foam structure or lattice structure coated with a reactive or catalytically active substance. The cleaning device is arranged in a convection generator space arranged above the space to be decontaminated or in an air recirculation duct such as a bypass between a lockable fresh air line and a lockable exhaust air line. The blower is a circulation fan for producing a circulating-air flow during the operation of the space to decontaminated. A high-efficiency mechanical filter such as an ultra-low particulate air-filter or a high-efficiency particulate air-filter is downstream to the blower in flow directions. The cleaning device is arranged between the blower and the high-efficiency particulate air-filter in the flow directions. A membrane is formed downstream to the high-efficien
