Abstract: The invention relates to a colorimetric dosimeter including an indicator housing openable at one end and having a wall defining an interior space extending along the length thereof. The housing is partitioned into a first portion starting at the one end and a second portion following behind the first portion. A strip indicator defines a high-sensitivity region and is disposed in the first portion so as to conjointly define a clear through diffusion passage with the wall which extends to the second portion. A granular indicator defining a low-sensitivity region is disposed in the second portion.