For two types of inner coating material of cathode ray tube (CRT) with different composition of water glass, the effect of air exposure in the atmosphere on the gas desorption was examined by using thermal desorption spectroscopy. The major outgassing species during the heating up to 773 K were CO₂ and H₂O in both the types. In the thermal desorption spectra of CO₂ and H₂O, a large desorption peak was observed at approximately 400 K. In both the materials, the amount of desorbed gases saturated at the exposure time of 1 h. Total amount of desorbed CO₂ and H₂O for the type with water glass content of (K₂O + Li₂O) ·3.8SiO₂·4H₂O was approximately a half of that for the type with water glass content of K₂O·3.8SiO₂·4H₂O. The surface morphology of the former type showed fine structure compared with that of the latter type. If the former type is used for the inner coating material, the manufacturing process of CRT may be shortened compared with that of the latter type.