A fluorescence-based method for highly sensitive and selective detection of volatile organic compounds such as vapors of benzene, alcohol, chloroform, dimethyl methylphosphonate (DMMP) that is a simulant of Sarin, Soman and other chemical warfare agents, is proposed. The method employs the effect of strong fluorescence change in thin films of aggregated porphyrins. In one preferred embodiment, the aggregation of porphyrin molecules leads to initial depression of chromophore emission due to self-quenching effect. The binding of analyte molecules to porphyrin sensitive layer forms porphyrin-analyte complexes, which destroy initial aggregate structure and induce the strong fluorescence enhancement. Aggregate-sensing films usually provide higher and faster response than porphyrins isolated in a polymer matrix. That results in strong enhancement of the florescence quantum yield and shift of the fluorescent spectrum in the direction of shorter wavelengths. The method can be used in fluorescence chemical sensors of organic vapors for different applications including environmental monitoring, control of industrial processes and medicine.