Essentials CO2 MonitorOverview The Essentials CO Monitor is a user friendly indoor air quality monitor, which detects CO levels using a Non Dispersive Infrared (NDIR) spectroscopic sensor. General Information Its large format display shows the real time CO level, ambient temperature and relative humidity, along with a clock and a bar chart indicating how CO levels have changed over the previous 24 hours. It can be set to give a green amber red backlight to indicate normal