external exposure facility CALLAB Paul Schofield The CERN Radiation Protection CALibration LABoratory (CALLAB), in service since 2015 and designed to ISO 17025 standards, is a state-of-the-art calibration facility for testing radiation protection instruments used at CERN and by external organisations. It houses Co-60 sources (up to 11.8 TBq), four Am-Be neutron sources (100 MBq–888 GBq), five Cs-137 sources (300 MBq–3 TBq), Kr-85 beta sources and an X-ray generator (up to 320 kV), providing H*(10) rates from tens of nSv/h to Sv/h across gamma, neutron, beta and X-ray fields. The Co-60 room also enables Total Ionising Dose testing of large systems up to ~1 m³. Located at CERN.