1. Design for real time monitoring ambiance carbon monoxide 2. LCD display detecting CO2 level, as well as temperature and relative humidity 3. NDIR infrared CO2 module inside with special ABC_Logic Self Calibration System. It makes the CO2 measurement more accurate and more reliable in use. 4. 15 years lifetime of CO2 sensor 5. Gentlest shape and convenient installation Structure 6. Particular LCD display with three color (Green/Yellow/Red) backlights 7. Two alarm ways: Buzzer alarm and backlight Colours switch 8. Provide optional 1xrelay output to control a ventilator 9. Easy touch button for operation 10. Provide four CO2 values to be preset to control The relay. 11. Optional RS485 communication interface, 15 KV Antistatic protection, individual IP address 12. Trusty quality with lower prices.