The influence of the strong acids HCl, HBr, and HI on the nitrogen laser-excited photoluminescence (PL) from a porous silicon (PS) surface is established. In contrast to the stabilizing effect of hydrochloric acid on a PS surface photoluminescing in doubly deionized water, HI almost completely quenches the photoluminescence. The effect of an HBr solution is intermediate. These observations focus attention on (1) the importance of ambient oxygen in the region of a photoluminescing sample and (2) the likelihood that the PS photoluminescence results exclusively from a surface bound triplet exciton with little contribution from low-lying singlet states.