The Dylos DC1100 Pro Air Quality Monitor is a true Laser Particle Counter with 2 size ranges – small (bacteria, mold, etc) large (pollen, etc.) DC1100 features technology and engineering that allows monitoring of indoor air quality with an LCD screen that provides small and large particle counts with a dynamic bar graph showing actual count reading. Multiple modes including minute, hour, day and monitor to evaluate your air quality and store up to 30 days of air quality history for review. DC1100 Pro has all the features of the standard DC1100 but with increased lower sensitivity – detecting particles down to 0.5 micron. The large particle size range is calibrated to 2.5 microns and above.