The solid-matrix room-temperature luminescence intensities and phosphorescence lifetimes of 4-phenylphenol and 2-phenylphenol adsorbed on filter paper without salt or with either NaCl, NaBr, or NaI were obtained over a wide range of relative humidity values in a nitrogen atmosphere. The solid-matrix fluorescence intensities showed very little dependence on relative humidity, whereas the solid-matrix phosphorescence intensities were very dependent on the magnitude of the relative humidity. Interestingly, the phosphorescence lifetime were not affected much by relative humidity. The results were interpreted with static and dynamic quenching models. These models indicated that moisture did not diffuse readily to the phosphors, and the complex cellulose network protected the phosphor from moisture. The changes in the phosphorescence intensities were attributed to the change in the modulus of filter paper as the humidity increased. 15 refs., 5 figs., 2 tabs.