In this paper, nanocomposite durability sensors were developed in order to detect the diffusion of chemicals in real-time. Polymer nanocomposite based sensors usually consist of conductive nano-additives such as CNT (carbon nanotube), graphene, carbon black, silver nanoparticles, etc. However, these nanocomposite sensors use a high content of nanomaterials to ensure good conductivity. In this study, a special approach for a chemical sensor with a low concentration (0.1 wt%-2 wt%) carbon nano-additive was carried out and tested in the 1[M] H3PO4 solution. Responding time and electrical resistance of each stage were analyzed against the nano-additives’ concentration. The sensing behavior is represented by the decrease of electrical resistance from 100 MΩ level to 100 Ω level. A numerical multi-stage model was developed to evaluate the formation of the conductive network and its sensing property. The modeling work shows two major parameters affect the sensing behavior: (1) The aspect ratio of conductive nano-additive. (2) Diffusion coefficient ratio of different ions in different phases.