We report on the preparation of photoluminescent porous InP by the application of high voltage spark discharges in air and in atmospheres. The spark-processed porous (spp) samples were characterized by the observation of their visible photoluminescence (PL) when illuminated with UV monochromatic radiation. Important differences are observed in the PL spectra of the spp-InP according to the atmosphere of preparation under similar conditions. Both the spp-InP prepared in air and in argon after air exposure show three similar broad peaks at energy positions 1.85, 2.43 and 3.1 eV. The pi, in the spp-InP can be understood as originating from quantum confinement effects of the InP radioactive regions in crystallites of nanometric dimensions, as result of the analysis with the well known model in the literature of the recombination of an electron-hole pair interacting inside a nanometric size sphere. The average size of the radiative active InP core in these crystallites is of the order of 42 Angstrom. We present evidence that oxygen plays a crucial role in the PL excited in the spp-InP. This is reinforced by XPS measurements that indicate that the spp-InP crystallites are covered by an extra oxidized shell of at least 30 Angstrom in thickness.