Because of the rise of anthropogenic sources of NP human exposure to NP has dramatically increased in the recent years, in the general population as well as in workers (e.g. welders). This raises the question of the potential adverse effects of NP on human health particularly at the respiratory level since it represents the main route of exposure for air pollutants. Since inhalation exposure is the most relevant but yet under evaluated route of exposure for the evaluation of NP toxicity our study was aimed to design, built, and characterize a safe inhalation system dedicated to evaluate the respiratory effects of NP in mice. We chose to focus on the generation of iron (Fe) and manganese (Mn) oxide NP distributions centered on 20-25 nm diameters at concentrations of 107-108 NP/cm3 as it is representative of the occupational exposure of welders. Fe and Mn NP aerosols were generated with the spark discharge generator technique with air as a carrier gas conditio sine qua non for the mice. Indeed the spark generator has been widely studied and used but in noble gases (N2, Ar,..) suggestion the absence of oxidation. Aerosol particles are characterized in terms of size distribution, concentration, morphology, and chemical composition. Exposure of mice for 1 to 4 days (3 hours a day) to these occupationally relevant aerosol concentrations induces inflammatory effects (increased lung total protein content). Moreover and clusters of particles were observed throughout the lungs.