The filter-ventilator unit serves for the removal of the explosive gases and the protection of the military post against the enemy’s chemical weapon. In case of a chemical attack, the air delivered into the unit gets cleaned in the filters which are half stuffed with absorbent coal and swansdown. Household equipment, combat rations, drinking water and kerosene could also be stored in this compartment.
Next to the filter room there is the engine room, which is the core element of a pillbox. A petrol-electric generator set AL - 12/2 (which is a gasoline-powered engine connected with an electric generator) was the main source of power, and a fixed heater was used both for its cooling and heating. Gasoline was used as a fuel, and its supply was stored in the generator set fuel tank and in a separate cistern.