The behavior of a polybutadiene-carbon black composite entering into contact with organic solvents and gasoline was investigated. The composite used has a conductivity of 3.0 +/- 0.1 Omega(-1) cm(-1). However, if it comes into contact with organic solvents (gasoline, for instance) the matrix absorbs them and consequently swells. This swelling causes the separation of the carbon particles and the concomitant diminution of the composite conductivity. During the tests performed, the resistivity of the composite grows exponentially with the exposure time to solvents. Typically, the material samples show a reduction of approximately 30% of its initial conductivity after only 1.5 min of exposure to solvents. Also, it was observed that the rate at which the conductivity decreases is related to the chemical nature of the solvent used in the test. To model the drop on composite conductivity induced by solvent swelling we use an effective media percolation approach. This approach was adapted to the needs of our experiments by modifying the definition of one of its main parameters (the critical volume of the low-conductivity fraction). The experimental data were successfully described by this model. Finally, the test performed shows that this composite is a very promising material that can be employed, for example, in various security and control devices to warning of accidental organic solvent or hydrocarbon leaks in pipelines or containers of chemical industries and refineries.