TNB Naturals CO2 Monitor (12/Cs) TNB Naturals CO2 Monitor and Thermo Hygrometer is a sleek portable unit that has been developed to monitor and display CO2 concentration, ambient temperature and relative humidity, along with the year, month, date and time. The monitor has a 3.5 inch LCD display and is USB compatible with a logging memory of 12,700 units. It has an accuracy of + or - 50 ppm and has the capability t... This item is sold individually. — Ships from SS: WA, CA, CO, MI, TN, PA, FL USA. Note: the WA warehouse is moving in Jul & Aug, some orders may be delayed 1-2 days....more info.