Abstract

Since the COVID-19 pandemic, the ventilation of school buildings has attracted considerable attention from the general public and researchers. However, guidance to assess the ventilation performance in classrooms, especially during a pandemic, is still lacking. Therefore, aiming to fill this gap, this study conducted a full-scale laboratory study to monitor the CO2 concentrations at 18 locations in a classroom setting under four different ventilation regimes. Additionally, a field study was carried out in two Dutch secondary schools to monitor the CO2 concentrations in the real classrooms with different ventilation regimes. Both the laboratory and field study findings showed that CO2 concentrations varied a lot between different locations in the same room, especially under natural ventilation conditions. The outcome demonstrates the need of monitoring the CO2 concentration at more than one location in a classroom. Moreover, the monitored CO2 concentration patterns for different ventilation regimes were used to determine the most representative location for CO2 monitoring in classrooms. For naturally ventilated classrooms, the location on the wall opposite to windows and the location on the front wall (nearby the teacher) were recommended. For mechanically ventilated classrooms, one measurement location seemed enough because CO2 was well-mixed under this ventilation regime.

Highlights

  • The ongoing pandemic of the Coronavirus disease 2019 (COVID-19) has created public concern about indoor air quality (IAQ) and room ventilation, especially in public spaces with many people such as school buildings

  • The results showed that the variation of CO2 concentration in the naturally ventilated classrooms was more obvious than the variation in the mechanically ventilated classrooms, which is consistent with results reported by Wohlgemuth and Christensen.[27]

  • A full-scale experiment was conducted in the Experience room of SenseLab to investigate the distribution of CO2 concentration under different ventilation regimes

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Summary

Introduction

The ongoing pandemic of the Coronavirus disease 2019 (COVID-19) has created public concern about indoor air quality (IAQ) and room ventilation, especially in public spaces with many people such as school buildings To determine whether such a space is ventilated properly, the CO2 concentration is monitored and used as a proxy for ventilation performance.[1] The history of CO2 as an indicator of the amount of ventilation can be traced back to 1858.2,3 Later, CO2 monitoring became gradually a convenient way to monitor IAQ.[4,5,6] A CO2 concentration of 1800 mg/m3 (or 1000 ppm) was often taken as the upper limit for a good IAQ, according to the previous version of ASHRAE (American Society of Heating, Refrigerating and AirConditioning Engineers) Standard 62-1989, Ventilation for Acceptable Indoor Air Quality. Relevant standards[7] mainly use minimum ventilation rates as the design criteria, while CO2 is the most commonly used tracer gas for calculating ventilation rate.[8,9,10] To date, many studies have been conducted to measure the CO2 concentration in school classrooms around the world to examine whether the ventilation performance in classrooms fulfils the requirements.[9,11,12,13] CO2 monitoring protocols used in these studies varied a lot: the selected number and location of sensors mainly depended on researchers’

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