Recently, the bactericidal efficiency of a low-pressure plasma process using a pure N2 flowing post discharge was demonstrated [Eur. Phys. J. Appl. Phys. 34, 143 (2006)]. In order to use this process for the decontamination of medical fiberscopes and endoscopes and more generally for the industrial decontamination of hollow bodies, the ability of the nitrogen atoms (which are believed to be the main decontamination agent) to flow in low diameter tubes (between 2 and 8 mm i.d.) without massive destruction is checked. The dependence of the N-atom concentration with the length, the internal diameter and the material of the tubes is studied and quantified. It is shown that the N-atom concentrations measured at the outlet of a polyamide tube of 6 m in length and of a 0.2 m long stainless steel tube are sufficient enough to provide high inactivation levels.