CO2 sensor versus Volatile Organic Compounds (VOC) sensor – analysis of field measurement data and implications for demand controlled ventilation

The study investigated performance of two commercially available non-selective metal oxide semiconductor VOC sensors and two commercially available non dispersive infrared CO2 sensors installed in one person office. The office was equipped with demand controlled ventilation. The signals from VOC and CO2 sensors, presence detection sensor and supply/return air flow were logged. VOC and CO2 signals were in agreement with respect to indicated need for mechanical ventilation for 49 % of occupied time (81 % of whole measuring period). VOC measurement would clearly trigger the mechanical ventilation in contradiction with CO2 measurement in 11 % of occupied time. Opposite situation was observed in 6 % of occupied time. In approx. 22 % of occupied time CO2 signal has just reached the set-point while the VOC signal was significantly below. In that case the ventilation start up would be dependent on settings of a particular controller.