The miniature diffusion size classifier (or miniDiSC for short) is a new instrument for nanoparticle measurement. It was designed with ease of use in mind - it is truly handheld, operates without working fluids or radioactive sources, operates in any orientation and on-the-go. It can be used for personal exposure monitoring or quick walk-through surveys of an area of interest, such as a workplace, or an urban area with heavy traffic. Its concentration detection limit is ideally suited for typical ambient particle concentrations. The miniDiSC is less accurate than traditional aerosol instruments such as CPC (condensation particle counter) and SMPS (scanning mobility particle sizer), available from e.g. TSI or Grimm, but this is often more than compensated for by its smaller size and easier handling. In general, measured concentrations and average diameters agree to within 30% with CPC and SMPS. Compared to its main competitor (the handheld CPC) it is smaller, easier to use and also delivers an average particle diameter and lung-deposited surface area and not only the particle number concentration. The handheld CPC is better suited when only number concentration is of interest, and when particle concentrations are below 1'000 per ccm.

The miniDiSC is ideally suited for all measurements where accuracy is not quite as important as ease of use. Its number concentration range is approximately 1'000 - 1'000'000 particles/ccm, which covers typical ambient particle levels (but not clean-room particle levels). We can customize it with less sensitive electrometers to measure higher particle concentrations if necessary, such as can occur in workplace settings. The miniDiSC can only size particles smaller than about half a micron correctly, and is thus not suited for microparticles. Typical applications of the miniDiSC are

• Personal exposure monitoring
• Workplace hazard identification
• Filtration efficiency verification
• Air pollution mapping with one mobile or multiple stationary instruments

In most cases, a quick measurement with a miniDiSC will answer the question whether or not there is an air quality problem in a given area.