Patent Number: 
Section: claims

1. A ventilation system for an operating space accessible to operators in a nuclear installation, the ventilation system comprising:an external inlet;a supply air line guided from said external inlet to the operating space;a first fan connected in said supply air line;a first inert gas adsorber column connected in said supply air line;an external outlet;an exhaust air line guided from the operating space to said external outlet;a second fan connected in said exhaust air line;a second inert gas adsorber column connected in said exhaust air line;a switching device for interchanging roles of said first and second inert gas adsorber columns;a circulating-air line;a CO2 adsorber column connected in said circulating-air line; anda circulating-air fan connected in said circulating-air line, said circulating-air line leading away from and back to the operating space, said second fan being able to be connected into said circulating-air line as said circulating-air fan. 2. The ventilation system according to claim 1, wherein said circulating-air line having an inlet side connected to said exhaust air line and an outlet side connected to said supply air line. 3. The ventilation system according to claim 1, wherein said first fan is disposed upstream of said first inert gas adsorber column, viewed in a direction of flow of supply air. 4. The ventilation system according to claim 3, further comprising at least one of a throttle or an air dryer connected into said supply air line between said first fan and said first inert gas adsorber column. 5. The ventilation system according to claim 1, wherein said second fan is disposed downstream of said second inert gas adsorber column, viewed in a direction of flow of exhaust air. 6. The ventilation system according to claim 1, further comprising a throttle connected into said exhaust air line upstream of said second inert gas adsorber column, viewed in a direction of flow of exhaust air. 7. The ventilation system according to claim 1, further comprising:an iodine filter connected into said supply air line; andan aerosol filter connected into said supply air line. 8. The ventilation system according to claim 7, wherein said iodine filter and said aerosol filter are disposed upstream of said first fan, viewed in a direction of flow of supply air. 9. The ventilation system according to claim 1, further comprising a stand-alone power supply module. 10. The ventilation system according to claim 1, wherein said switching device contains a plurality of 3-way valves. 11. A method for operating a ventilation system for an operating space accessible to operators in a nuclear installation, which comprises the steps of:connecting into a supply air line being guided from an external inlet to the operating space, a first fan and a first inert gas adsorber column;connecting into an exhaust air line being guided from the operating space to an external outlet, a second fan and a second inert gas adsorber column;providing a switching device for interchanging roles of the first and second inert gas adsorber columns;flowing supply air through one of the inert gas adsorber columns and the one inert gas adsorber column thus being loaded with radioactive inert gases, and exhaust air simultaneously flowing through the other inert gas adsorber column and the other inert gas adsorber column thus being backwashed, and in which roles of the first and second inert gas adsorber columns are interchanged by switching as soon as an adsorption capacity of a currently loaded inert gas adsorber column is exhausted; andproviding a circulating-air line, into which a CO2 adsorber column and a circulating-air fan are connected, the circulating-air line leads away from and back to the operating space, pressure being built up at least in one of the inert gas adsorber columns by means of the first fan, and, simultaneously, CO2 reduction being carried out by the CO2 adsorber column in a circulating-air mode. 12. The method according to claim 11, wherein, while the pressure is being built up, the operating space is ventilated exclusively by circulating air decontaminated from CO2. 13. The method according to claim 11, which further comprises simultaneously feeding supply air to the operating space by means of at least one of the inert gas adsorber columns, and CO2 reduction is carried out by the CO2 adsorber column in the circulating-air mode. 14. The method according to claim 11, which further comprises using the first fan as the circulating-air fan.