Novel aerosol diluter-Size dependent characterization down to 1 nm particle size

Ultrafine particles (UFP, < 100 nm) often dominate the aerosol number concentration in urban environments. The resulting high particle concentrations can be as high as 106 particles cm-3. Such high concentrations are a challenge for the instruments, as the measurements based on condensation particle counters, are typically designed to be sensitive for lower concentrations. Therefore, a diluter is often employed to lower the concentrations down to the measurement range of the instrument. However, diluters are often unsuitable for measuring cluster or nucleation mode particles due to high losses. Here, we present the new Airmodus nanoparticle diluter (AND) sampling system and characterize its performance at different dilution factors over a wide particle size range down to similar to 1 nm size. In addition to diluting the sample, AND can be used as an ion precipitator to remove small ions from the sampled air or to lower the relative humidity of the sampled air. The first results from the ambient traffic emission measurements are also shown.