Characterization of a compact water CPC for portable use

The water-based condensation particle counter (WCPC) was introduced by Hering and Stolzenburg in 2004, and since then, the technique has been in wide use for determining the concentration of ultrafine particles in air.

The counting efficiency of a CPC is measured by introducing a known, monodisperse aerosol to the CPC and a reference measurement system, simultaneously. The reference measurement system that is used is often an electrometer. The particle size of the monodisperse aerosol is varied across a wide, but especially near the lower end of the detection limit. The efficiency of the CPC as a function of particle diameter can then be plotted and assessed. The d50, or diameter at which 50% or more of the particles of that diameter are counted by the CPC is then known, and serves as a useful parameter in understanding the results from the CPC.

Typically, water-based CPCs are used in a fixed laboratory setting, and as such, are not easily portable. There exist a number of applications that could benefit from the use of a small and portable WCPC solution. Here, we show the characterization of a new single-channel portable WCPC (model 3001) which weighs 1 kg and has volumetric dimensions of 16 × 12 × 8 cm.

The counting efficiency of the 3001 was assessed by testing 5 units simultaneously on monodisperse NaCl particles generated in a tube furnace and classified by a 3082 classifier and 3085 differential mobility analyzer (DMA) and compared with a 3068B electrometer. The d50 was found to be ~8nm. The concentration accuracy was found to be better than 20% up to 200,000 particles/cc at standard conditions. These results suggest that the 3001 can be useful for mobile measurements of ultrafine particle concentrations in a variety of research and monitoring applications.