Absorption of nitrogen dioxide from a flue gas in an aqueous solution leads to the formation of nitrous and nitric acids. Nitrous acid is not stable and decomposes into nitrogen monoxide which is more pollutant than nitrogen dioxide. To avoid that reaction, nitrous acid can be reduced to non-pollutant products through specific reagents. The aim of this work is the reduction of nitrous acid by urea or sulfamic acid in a mechanically stirred closed reactor. Under different operating conditions (temperatures from 5 to 38 degrees C, pH between 1 and 4, initial nitrous acid concentration 0.001 or 0.002 kmol m(-3), urea or sulfamic acid concentration between 0.002 and 1 kmol m-3), our results allow us to confirm that the kinetics of reaction are of first order with respect to nitrous acid and with respect to the reductor. Values of rate constants as a function of temperature are given at pH = 1 for urea and at pH = 3 for sulfamic acid. Within the studied range of pH, reactivity of sulphamic acid is greater than that of urea.