<p>Formulations based on explosives with reduced vulnerability to mechanical stimuli and high thermal stability, e.g. nitrotriazolone, are used to produce insensitive munition. NTO has similar performance characteristics to commonly used explosives such as RDX and HMX, but is much less sensitive to accidental initiation due to heat, impact or spark. In order to forecast the thermal stability of explosives, as well as to determine for what period they can be safely operated, the accelerated ageing process is carried out, making it possible to predict changes in the initial properties of explosives during storage and to assess the impact of ageing on safety. This work aimed to obtain low-sensitive explosive compositions based on 3-Nitro-1,2,4-triazol-5-one and investigate the impact of accelerated ageing on their selected thermal and physicochemical properties. Two melt-cast compositions based on TNT and containing NTO were prepared and subjected to accelerated ageing. Samples were subjected to tests such as thermal analysis (including the kinetics of thermal decomposition), friction and impact sensitivity tests, as well as density measurements to determine the effect of ageing on, among others thermal properties, sensitivity to mechanical stimuli and density. As a result of accelerated ageing, all compositions changed colour. Sample submission to an ageing process did not adversely affect their sensitivity to friction and impact or thermal decomposition activation energy. Thermal decomposition of compositions is a complex process with an autocatalytic phase.</p>