The bunkers filter system

Full description of the bunker here: [link]

The filter system of the nuclear bunker Steintorwall is comparable with an over-dimensional vacuum cleaner which instead of a bag has got a filter attached to it.
In the first picture, you can recognize the structure of the filter. The upper layer is made of filter sand. Its purpose is to filter the big particles. After that, the air is sucked through granular activated carbon. Small particles are filtered during that procedure.
In the third picture, you can see a part of the filter system with radiation blocks halfway stacked up (the filters will have eventually absorbed to much radiation and particles to function propely and it would be dangerous to move them somewhere else, so they are left in the same room and are only quickly replaced with a "clean" filter).

Fourth picture says "ABC-Filter - Dont take blocks away - Danger through radiation!"