Temperature Carbon dioxide (CO2) is a measure of the average kinetic energy of molecules in a sample of air. It is commonly used to determine the temperature of the surrounding environment. Temperature CO2 is typically expressed as parts per million, or ppm, and can range from 0 ppm (freezing) to 600ppm (high temperatures). By monitoring the levels of CO2 in an environment, businesses can identify potential issues, such as low airflow, high temperatures, or insufficient ventilation.