In practice, it is generally not appropriate to use CO2 sensors to monitor indoor air quality in buildings without densely occupied spaces, since the sensors are designed for optimal use in those types of spaces.  CO2 sensors are not substitutes for

In practice, it is generally not appropriate to use CO₂ sensors to monitor indoor air quality in buildings without densely occupied spaces, since the sensors are designed for optimal use in those types of spaces.  CO₂ sensors are not substitutes for required equipment used to continuously monitor outdoor airflow rates, but rather are supplementary monitors that can be useful in buildings containing densely occupied spaces (see Case 2 below).