Used for monitoring the dust content in Microgram per meter cube. Indicate 5 levels by 5 colorsz Blue 03-35μg/M Green : 36-70μg/M3 Yellow : 71-150μg/M3 Orange : 151-250μg/M3 Red : 251over μg/M3 ? Equipped with three modes ? NOW mode / HOUR mode / DAY mode Measurement Principle : Light Scattering Method Measurement Range : 0 – 999 μg/m3 Measurement Time : 8 seconds Measurement Accuracy : +/- 15% Operating Temperature : 0 to 45 degreeC Storage Temperature : -10 to 60 degreeC Display : Custom Segment LCD (with backlight) Power Supply : Alkaline AA Battery x 2 (or USB cable) Battery Life : About 200 times Size : W62 x H123 x D47mm Weight : Approx. 200g (including batteries)