For some years, the characterization of workers' exposure to airborne metallic ultrafine particles (UFP) has been an increasing issue because of their effects on health, and as many activities are potentially concerned (welding, oxycutting, 3D printing ...). Determining the particle size distribution of such an aerosol provides a real contribution to the understanding of UFP exposures and associated health effects, as it is directly related to their penetration in the respiratory tract. In this context, it is proposed to optimize the preparation of cascade impactors collection substrates for airborne metallic UFP. The experimental results show that the collection substrates have to be prepared beforehand by coating them following a procedure (nature and amount of the coating grease) in order to obtain reproducible and representative particle size distributions. Indeed, this optimization allows the phenomena of particle bouncing and particle reentrainment to be reduced.
