This standard provides guidance for measuring the concentration and size distribution of ultrafine aerosols and nano aerosols using a mobile particle analyzer (also called differential mobility analyzer). In this case, only the particle fraction of the aerosol is considered. For ultrafine aerosols and nano aerosols, exposure matrices such as water concentration and surface area concentration are important. This standard also provides guidance for measuring exposure in the workplace of ultrafine aerosols and nano aerosols. In particular, we will discuss the differential mobility analysis system (DMAS) marketed by several suppliers. It also deals with operating principles, sample collection problems in the workplace environment, calibration, equipment maintenance, measurement uncertainty, and reporting of measurement results. And potential problems and limitations that must be addressed when taking compliance measures under specified exposure standards.