Abstract  The variety of SiO₂-gel structures allows the use of sol-gel derived materials as host matrices for prolonged release of chemicals. In this work, the release of perfumed essences is studied in the case of hybrid SiO₂ materials obtained from alkyl-modified silicon alkoxides. Thermogravimetric analysis in isothermal conditions at various temperatures provide data on the kinetic release process. The effects of physical parameters (porosity reduction, vapour pressure) and chemical interactions (organic molecules with matrix) are discussed for the interpretation of the results.