features: Fast warm up time.Audible warning.USB power supply.Backlight display function.Data Memory and Recall function.Continuous data logging with time/date.Precise Adjustment in different barometric levels (or pressures).CO2: 0 9, 999 ppm range, diffusion sampling mode.Data hold & Maximum / Minimum with time stamp.Energy Efficiency by sampling time modulation.Easy to use USB interface and user friendly software.Large Dual LCD Display for CO2, %RH humidity and temperature.