An optical sensor for oxygen detection based on the immobilization of tris 1,10-phenanthroline ruthenium (Ru(phen)(3)) into polystyrene (PS) films was employed for monitoring the oxygen permeation through polymeric packaging films. 7-Methoxy-4-methylcoumarin was selected as non-sensitive reference to oxygen and dispersed with the Ruthenium complex in order to develop a ratiometric sensor correcting the artifacts induced by operating conditions and improving the robustness of the sensor. The developed ratiometric sensor was successfully employed for the measurement of the oxygen permeation rate in an enclosed atmosphere (package) using polymeric films made of biaxially oriented polypropylene (BOPP) and polydimethyl siloxane (PDMS). It was observed that the oxygen concentration in the enclosed atmosphere increased from 0% to 21% in 3 h in the case of PDMS and from 0% to 3.6% in 24 h for BOPP. The concentration evolvement with time was well predicted by a solution-diffusion model and the final oxygen concentration in the packed atmosphere was confirmed by chromatographic measurements. According to these results, the ratiometric luminescent sensor is suitable for the development of smart packaging films allowing for continuous monitoring of oxygen concentration in-situ. (C) 2016 Elsevier Ltd. All rights reserved.