Aerosol particle counters are built to rapidly count and size contaminant particles in cleanroom air and other controlled environments. Users tend to see this as a device where a button is pressed and absolute results tumble out. However, when measuring anything small, it is important to be aware of the technology within the instrument to understand the relevance of the data generated, to put the operation of particle counters in context, and to be aware of its benefits and limitations. No measurement is absolute―all are relative to the measuring technique employed. For example, if we measure particles with a scanning electron microscope, it would not be a surprise to get slightly different results. We might even get vastly different results at certain sizes, because that particular technology is producing a response which differs from that produced by the particle counter.
