The loss probability gamma(N) of nitrogen atoms is measured versus the temperature on different surfaces by a method based on optical emission spectroscopy measurements. In a cylindrical quartz tube, a late Ar-N-2 post-discharge is used. Emission of the first positive system is observed in a zone that precedes a heated zone and in another zone that follows it. Each observed zone is at room temperature. Indeed, in these conditions, nitrogen atoms titration by NO permits the attainment of the absolute value of the N density. This method can give the dependence of the loss probability of nitrogen atoms versus the temperature. The very simple geometry used here enables the use of foils made of any material introduced in the heated zone of the reactor. Therefore, different wall materials can be easily studied. Calculation of the loss probability gamma(N) requires a 2D hydrodynamic. thermal and kinetics modelling. It was developed and it included, diffusion to the walls, temperature gradients, volume and surface nitrogen atom consumptions. The first results obtained on quartz show that N atoms recombine according to an Eley-Rideal mechanism and gamma (N/quartz) = 9.3 x 10(-5) exp(-3700/RT). The loss probability of the N atoms was also determined at 300 K on iron foils. The weak value obtained gamma(N/iron) = 6.7 x 10(-4) is probably due to the nitriding of the metal.