The OSL selective dosimetrical materials based on CaS doped with Bi and In ions were synthesised. Physicochemical properties of such materials are analysed in detail and a model of traps and recombination centres is proposed. For CaS-In phosphors the emission in the range of 2.4-2.1 eV is assigned to the defect Me 3+ Me + or Me 3+ Me - , whereas for CaS-Bi phosphors the centres B1 3+ or B1 3+ Na + are responsible for the emission at 2.7 eV. The traps revealed in OSL are attributed to intrinsic defects of CaS (energy level of 1.65 eV) and to a single Me 3+ state (1.35-1.45 eV). The α/γ ratio of 2000 (arb. units) is reached for the best OSL CaS-In samples synthesised. However, the presence of fading for elaborated OSL dosimetric materials needs further improvement in technology.