When you readout your dosimeter at the reader stations, the dose value displayed in mSv has been corrected for the natural background contribution. It is therefore normal that the value shown is 0 or close to 0 if you have not been exposed to ionising radiation or only to very low levels of radiation since the assignment of your dosimeter. The background subtraction is the same for all CERN locations, however the background is not the same within the larger CERN boundaries. If the background at you location is lower than 2.3 µSv/day your dosimeter is slightly over-corrected and this is why it might always be at 0.

If you have been accessing Radiation Areas and expected that you took a dose well above 0 ( > 100 µSv), please get in contact with the Dosimetry Service.