AQ Guard Smart 2000 is a measuring device for monitoring particle concentrations in the ultrafine range. These ultrafine particles (UFP) significantly impact health, according to the World Health Organization (WHO). The WHO has therefore been recommending their monitoring since 2021. They typically cannot be detected by optical aerosol photometers or spectrometers due to their small size

Mass limit values such as PM2.5 and PM10 can be measured well with gravimetric methods; at the latest, for smaller PM1, ultrafine fractions are difficult to estimate and can be meaningfully assessed only by determining the particle concentration.

Expensive and more maintenance-intensive condensation particle counters are usually used to measure ultrafine particles. A size-classifying system (Scanning Mobility Particle Sizer) can make statements about particle size distribution and concentration