The main requirement of the Breathing Air systems (SCBA, Cascade or BAS for personnel) is to assure the vital condition for the survival or people inside Temporary Refuges or Muster Area during determinate situations. The operating philosophy of this systems is focalized on the possibility that they can be running also during emergency conditions (as example on determinate concentration of hydrocarbon gasses on outdoor atmosphere and the stop of HVAC system and electric power)