Poor indoor air quality has been demonstrated to increase the risk of transmitting infectious agents and to expose individuals to the phenomenon of sick building syndrome. In light of these findings, most countries have established specific guidelines regarding indoor air quality in university rooms. In France, for instance, the maximum permissible concentration of carbon dioxide (CO2) in university rooms without mechanical ventilation is set at 1,300 parts per million (ppm), and the minimum volume per occupant is 15 m3. For rooms with mechanical ventilation, the minimum clean air flow rate is 25 m3/h/occupant.

The primary objective of this study was to design and demonstrate the feasibility of a simple, cost-effective method for comparing the reality of indoor air quality in all university rooms with legal requirements. The secondary objectives of the present study were to demonstrate the efficacy of the proposed method in identifying and reporting problematic situations, and in issuing practical recommendations.

Mobile CO2 sensors (Aranet4) were provided to volunteer lecturers to measure the CO2 concentration during and after classes. The number of occupants and the condition of openings were also recorded. These data were supplemented by measurements from 117 fixed Carbon Nexelec sensors. The data were then fitted to a model, which enabled the characterization of air quality and the estimation of the gauge reduction required to comply with the law.

None of the 14 rooms without mechanical ventilation complied with the legal minimum of 15 m3/occupant. 75% of the third quartiles of CO2 concentrations during classes exceeded 2692 ppm. In rooms with mechanical ventilation, median clean air flow was 15 m3/h/occupant at 100% occupancy (9 m3/h/occupant for the first quartile). In 32 out of 41 rooms with mechanical ventilation (78%), the clean air flow was estimated to be below the legal minimum of 25 m3/h/occupant at 100% occupancy. Concentrations in excess of 5,000 ppm were observed in 23 of the 101 rooms equipped with fixed sensors.

The proposed method has demonstrated its feasibility in real-life conditions. For the purpose of evaluating the air quality of all rooms affiliated with universities, it is recommended that this method be used in a systematic manner. The findings of this study indicate that a significant proportion of the examined rooms may not be in accordance with the relevant legislation, thereby jeopardizing the health of the occupants. In order to comply with the law, the method proposed here to estimate gauge reduction should be applied.

The authors have declared no competing interest.

The 4 Aranet4 CO2 sensors were funded by SNESUP-FSU union. The author is an employee of University Grenoble Alpes (France).

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The data used to support the findings of this study are available from the corresponding author upon request.