Day after day, new applications using manufactured nanoparticles appear in industry. To evaluate the occupational risk associated to nanoparticles, it is important to have reliable, accurate and standardized measurement methods. It is therefore necessary to work on pre-normalization projects to develop reference methods to characterize the number and the size distribution of airborne nanoparticles. The aim of this pre-normalization project is to develop characterization methods for airborne nanoparticles that include all the measurement chain (sampling, analysis, data treatments, etc.) which will be traceable, adequate and accurate: this project includes the estimation of the uncertainties on the measurements. This presented study, first step of this project, describes the generation and the characterization of SiO2 airborne nanoparticles from a liquid manufactured suspension. Experiments have been performed in order to study the stability and the repeatability of the generation protocol of SiO2 airborne nanoparticles by measuring their count size distributions with a Scanning Mobility Particle Sizer (SMPS).