Sensing composite materials involving various kinds of polymer and carbon nanomaterial could be used as strain or gas sensors. The basic construction of sensing composites is based on polymeric matrix, nonwoven structure and conductive particles or fibres. In order to create the entanglement network of nonwoven structure, electro-spinning process was involved. The nonwoven structure was used as filter which was filled with sensing fibres or particles and finally the full filter was pressed into polymeric matrix. To improve sensitivity, the effects of various treatments of conductive particles/fibres were tested under various conditions. Testing has shown that the composite has favourable properties as a highly-deformation strain sensing element in the course of both a monotonic and dynamic elongation cycle/process. Another investigation was connected with adsorption of gas molecules on conductive nonwoven structure which affects their electrical behaviour. Various dependencies among surface treatment, nonwoven structure, deformation strain and selected gases will be presented with respect to future applications.