Quenching of luminescence by oxygen of ruthenium diphenylphenanthroline in various polymers was studied by time-resolved spectroscopy. The luminescence decay was not single exponential, and the Stern-Volmer plot was nonlinear (downward-curved) in all cases. A new model for describing the nonexponential luminescence decay was developed, which considers the interaction of the fluorophore with the nonuniform environment provided by the polymer. This model has a better physical basis than the usual fits with multiple exponentials or lifetime distributions of arbitrary shape. Oxygen quenching is described by a single parameter, which, in favorable cases, depends linearly on oxygen pressure. This may be of advantage for the calibration of optical oxygen sensors based on luminescence quenching.