The range of aerosol particle number concentrations found commonly in the atmosphere spans several orders of magnitude, from less than 100 particles per cubic centimeter in clean background environments, e.g. Antarctica or Finnish Lapland, to millions of particles per cubic centimeter in mega-cities or close to emission sources. Large variation in concentrations can occur also naturally within a small period of time, when new particles form from atmospheric vapors. This poses a challenge for the measurement devices. Condensation particle counters (CPCs) are ideal instruments for the cleaner environments, as they count individual particles with a good time resolution, but when concentrations exceed about 100 000/cc, a suitable method of dilution needs to be introduced in order to get reliable results.
The Airmodus Particle Size Magnifier system (A11) starts counting particles at a smaller size than any other CPC. Recently, we have been finding the extremes also in particle concentrations. Members of the PSM user community are performing measurements both in ultra-clean conditions in a clean room and at the CLOUD chamber, and on the other hand also in traffic environments and directly from engine exhausts.