Nano-objects with different chemical compositions and structures (shapes) are very important building blocks for nanostructured materials. The characterization of the nanoparticles in the gas phase during synthesis and their use is of great importance. The total nanoparticle surface area concentration is essential especially for describing interface processes, because of the increasing surface area per unit of mass with decreasing particle size. In this paper the possible use of an electrical sensor for measuring total surface area concentrations of spherical and agglomerated/aggregated nanoparticles in aerosols is discussed.