Environment protection is one of the most discussed topics today. Accordingly there is an increase in research and production of sensormaterials, which could detect leakages, monitor air quality and also could be used in industry for process control. Sensormaterial described above need to be at least sensitive to organic solvent vapour exposure limits determined by NIOSHA or OSHA. In the same time sensormaterial have to maintain response repeatability. Our scientific group have produced PNCC with 4 mass parts of carbon black and tested it to toluene vapour concentration 754mg/m3 (toluene TWA level). The composite electric resistance increased immediately with exposure to vapour. As reported previously [1] the composite electric resistance increase is due to tunneling current existence in thin layers of matrix between carbon black nanoparticles aggregates. Composite samples have been prepared by solution mixing of polyisoprene and carbon black particles, which were prior to dispersed into chloroform by sonification. After that a definite number of mixed solution layers (6, 8 or 10) were coated onto substrate (epoxy resin) with embedded brass wires. In this paper we will describe how variation of the composite carbon black content (4, 5 and 6 mass parts) near the percolation threshold influence organic solvent vapour sensitivity and repeatability.