By applying the IRAS technique (infrared-absorption-reflection spectroscopy) and electron stimulated desorption (ESD) of negative ions we demonstrate that a 10 monolayer (ML) film of NF3 is degraded in the course of low-energy electron irradiation in the range 0-5 eV which is far below the electronic excitation of NF3. Degradation is accompanied by the desorption of F- fragment ions from the film and formation of NF2 radicals and N2F4 molecules in the film. The energy dependence of the degradation cross-section follows that for resonant (dissociative) electron attachment in the low-energy region (approximate to 0-5 eV) and increases above 6 eV. We therefore identify (dissociative) electron capture at low energy as the only initial reaction responsible for the chemical changes in the NF3 film.