Estimation of children's CO2 generation rates in naturally ventilated educational buildings

Abstract

Indoor CO2 concentration serves as an indicator of indoor air quality, which is mainly influenced by occupants' CO2 generation rate, outdoor ventilation rate and outdoor CO2 levels. Determining the CO2 generation rate is fundamental to design effective ventilation systems that ensure good indoor air quality. The ASTM D6245 standard offers a method to estimate human CO2 generation based on sex, age, body mass, and activity level. However, due to the limited number of studies on CO2 generation rate for children and adolescents in daily scholarly activities, accurated values are difficult to estimate. This research uses a stochastic grey box modelling approach to estimate CO2 generation rates in naturally ventilated schools and compares it with the standard approach. This method can address the complexities and variations in real educational environments. The proposed model was verified through an experimental campaign including 32 classrooms with students aged 4, 10, 13 and 16 years. The model provided a detailed description of the indoor CO2 dynamics in 72% of the studied cases. Estimated CO2 generation rates were found to be in line with the expected standard value of between 1.0 MET to 2.0 MET activity levels (7.07–12.65 L/h for a 4-year-old, 9.63–13.29 L/h for a 10-year-old, 14.54–19.32 L/h for a 13-year-old, and 12.11–20.53 L/h for a 16-year-old). These findings not only bridge the gap in children's CO2 generation rates but also introduce a novel approach to assess human CO2 generation rates under uncontrolled conditions.