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Mitigating indoor risk of airborne infections using CO2 and PM measurements in university classroom: the MIRAI
Riccardo Mazzoli1, Tommaso Filippini1,2,3, Grazia Ghermandi4
1Environmental, Genetic and Nutritional Epidemiology Research Center (CREAGEN), Department of Biomedical, Metabolic and Neural Sciences, Section of Public Health, University of Modena and Reggio Emilia, Modena, Italy.
Background:
Indoor air quality (IAQ) impacts well-being and the spread of airborne diseases, particularly in multi-occupancy environments like classrooms. Carbon dioxide (CO2) and particulate matter (PM) levels have been used in continuous monitoring as indicators of indoor air quality.
Methods:
We used cost-effective sensors to assess levels of CO2 and PM in two Italian university classrooms (Unit 1 and Unit 2), differing in size and ventilation, from March 2022 to May 2023. For CO2 and PM monitoring we used respectively ARANET4 sensors and Optical Particle Counters (OPC) assessing aerosol diameter size distribution between 350 nm and 40 μm in order to evaluate trends in IAQ and the influence of environmental factors including ventilation, occupancy, and season.
Results:
The naturally ventilated classroom (Unit 1) exhibited higher CO2 and PM concentrations with greater variability, whereas the HVAC-supported one (Unit 2) maintained more consistent air quality but faced occasional spikes. Occupancy also affected CO2 and PM levels, with higher variability in Unit 1 characterized by lower size and generally full occupancy. Seasonal trends highlighted increased PM levels during colder months due to reduced ventilation in both units.
Conclusions:
In this feasibility study, variations in building design, ventilation strategies, and occupancy dynamics were associated with corresponding patterns in IAQ, supporting the use of low-cost, user-friendly sensors as practical tools to characterize ventilation performance and to inform interventions aimed at safer learning spaces. Implementation of CO2 and PM measurements as proxy indicators of ventilation adequacy and of potential airborne infection risk, along with outreach programs and guidelines to educate teachers and students about relevance of IAQ assessment is recommended to promote occupant health and mitigate risk of airborne disease transmission.
Supplementary Information:
The online version contains supplementary material available at 10.1007/s40201-026-00984-2.
Insights
Indoor air quality (IAQ) was monitored in university classrooms using low-cost sensors. Results show ventilation type and occupancy significantly impact CO2 and particulate matter levels, affecting health and disease spread.
Area of Science:
- Environmental Science
- Public Health
- Building Science
Background:
- Indoor air quality (IAQ) is crucial for well-being and preventing airborne disease transmission in shared spaces.
- Carbon dioxide (CO2) and particulate matter (PM) are key indicators for monitoring IAQ.
Purpose of the Study:
- To assess IAQ using cost-effective sensors in two distinct university classrooms.
- To evaluate the influence of building design, ventilation, occupancy, and season on CO2 and PM levels.
Main Methods:
- Utilized ARANET4 sensors for CO2 and Optical Particle Counters (OPC) for PM monitoring (350 nm–40 μm).
- Conducted continuous monitoring in two Italian university classrooms from March 2022 to May 2023.
- Compared naturally ventilated and HVAC-supported classrooms.
Main Results:
- Naturally ventilated rooms showed higher CO2 and PM concentrations with greater variability.
- HVAC-supported rooms maintained more stable IAQ, with occasional spikes.
- Increased PM levels were observed in colder months due to reduced ventilation.
Conclusions:
- Building design and ventilation strategies significantly influence IAQ patterns.
- Low-cost sensors are practical tools for assessing ventilation and informing interventions for safer learning environments.
- Recommends CO2 and PM monitoring as proxies for ventilation adequacy and airborne infection risk, alongside educational programs.
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