Fig. 5. Number, surface area and mass concentration of the growing mode after 48 h as function of the formation rate of 5 nm particles, J₅. The condensation sink of the background particle population, CS_background, has been assumed to be equal to 0.010 s⁻¹ (left panel) or 0.001 s⁻¹ (right panel). The other model inputs are: initial particle diameter = 5 nm, duration of NPF = 5 h, GR = 4 nm h⁻¹ and σ_geo = 1.7.