Pandemic experiences with manual ventilation and CO 2 - sensing in schools

Generally, classroom CO2 levels were shown to rise quickly in the morning, peaking in the late morning.5,6 MANUAL VENTILATION AND CO2 SENSING IN SCHOOLS 5 However, it is somewhat difficult to compare ventilation effectiveness among these studies due to a number of limitations or special considerations. [...] Did CO2 sensing improve ventilation effectiveness or reduce adverse impacts? Although the importance and utility of CO2 sensing to regulate classroom IAQ was a key assumption in all of the studies reviewed, the literature reviewed did not adequately demonstrate the additional value of CO2 sensing over and above the implementation of the ventilation protocol itself. [...] Classrooms that employed scheduled ventilation but no sensor were too cold 65.8% of the time, compared to only 41.8% of the time with scheduled ventilation and CO2 feedback, and 18.7% of the time with continuous ventilation and CO2 feedback. [...] In the first school, CO2 visual feedback appeared to elicit an MANUAL VENTILATION AND CO2 SENSING IN SCHOOLS 16 overall increase in window opening and decrease in CO2 levels compared to the classroom without a sensor, and thermal discomfort was largely avoided. [...] Some authors have used CO2 levels to calculate the “rebreathed” fraction of air in a given space, and then linked that fraction to the risk of infection and used the relationship to recommend CO2 thresholds for indoor spaces based on activity level, vocalization, and use of masks.30 However, as mentioned above, these studies do not account for the various ways virus levels may change or the differ.