The partitioning of nitrogen oxides in the atmosphere, in particular the NO_x/HNO₃ ratio, is not accurately reproduced by models. Although the model under-prediction of the NO_x/HNO₃ ratio has been improved by the new rate constants for the reactions of OH with NO₂ and HNO₃, a discrepancy between the field and modeled ratios is still observed. Heterogeneous reactions of HNO₃ with various atmospheric gaseous species, including NO, CO, CH₄ and SO₂, have been proposed to reconcile these ratios. We present laboratory studies in which the possibility of heterogeneous reactions between HNO₃ adsorbed on silica surfaces and gaseous NO, CO, CH₄ and SO₂ were investigated. Two different silica surfaces, a porous glass plate and pressed silica (Cab-O-Sil^®) pellets, were used as substrates for HNO₃. Both the gas phase and the surface species were monitored with time using FTIR at 1 atm total pressure in N₂ and 298 K. No reaction was observed between HNO_3(ads) and CO, CH₄ or SO₂, from which upper limits for the reaction probabilities (g^rxn) were derived to be equal or smaller than 10^-12 for SO₂, and than 10^-10 for CO and CH₄. The effect of Fe³⁺ and H₂SO₄ on the reaction with CO was also investigated, and no reaction was observed under either of these conditions. Nitric oxide does react with the undissociated form of HNO₃ adsorbed on the silica pellets, and not the anion NO₃^-, to form NO₂ and a water-nitric acid complex. A lower limit for the reaction probability of gaseous NO with HNO₃ adsorbed on silica pellets was calculated to be equal or greater than (6 ± 2) x 10^-9 (2s) for NO. The atmospheric implications of NO₃ “renoxification” on common silica surfaces will be discussed.