A25M (handheld) /A25D (benchtop) /A25F (benchtop) are air quality meters used to measure PM2.5 concentration.  A25F can also measure formaldehyde concentration. PM2.5/Formaldehyde concentrations display different emoticons on-screen to help users visualize their environmental conditions. Features: Precise PM2.5 concentration based on pre-calibrated sensors Temperature measurement (°C/°F) Humidity measurement Emoticon display LCD backlight and red backlight alarm Battery status, low power, auto power off Formaldehyde concentration Package Includes: 1 x Uni T A25F PM2.5 Meter