Smart Wireless CO2 Sensor Node for IoT Based Strategic Monitoring Tool of The Risk of The Indoor SARS-CoV-2 Airborne Transmission  
[PERSON]  
1 Department of Refrigeration, Air Conditioning, and Energy Engineering,  
National Chin-Yi University of Technology, Taichung 41170, Taiwan 1  
[PERSON]  
2 Department of Informatics Engineering, Faculty of Computer Science,  
Universitas Brawijaya, Malang, Jawa Timur 65145, Indonesia 2  
[PERSON]  
1 Department of Refrigeration, Air Conditioning, and Energy Engineering,  
National Chin-Yi University of Technology, Taichung 41170, Taiwan 1  
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Syndrome-Coronavirus-2 (SARS-CoV-2) infection, the monitoring IAQ is still a significant key to minimize the risk of SARS-CoV-2 airborne transmission [9]. Furthermore, the level of Carbon dioxide (CO\({}_{2}\)) concentration receives primary attention of IAQ monitoring systems today. Therefore, in many HVAC (Heating, Ventilation, and Air-Conditioning) systems, control of the fresh airflow rate mostly uses indoor CO\({}_{2}\) concentration as the indicator [10]. Moreover, the purpose of indoor CO\({}_{2}\) concentration measurement and monitoring is crucial, not only for CO\({}_{2}\) exposure effects evaluation but also for the study of airborne transmission of various contagious diseases, e.g., tuberculosis, measles, influenza, H1N1, and coronavirus (COVID-19). In other words, an indication of indoor airborne cross-infection risk can be evaluated based on the indoor CO\({}_{2}\) concentration level [11; 12; 13]. Multiple studies have demonstrated the SARS-CoV-2 virus's airborne transmission mainly through particles from respiratory inhalation that contains the virus [14; 15; 16]. The particles spread out during lung-related activities such as breathing, laughing, speaking, singing, etc. The particles are distinguished into two sizes that are droplets with large sizes and aerosols with small sizes. When larger particles spread in the air, they quickly drop to the ground, while smaller particles easily float and spread in enclosed spaces for a longer period [17]. Because CO\({}_{2}\) concentration has a close correlation with aerosol particles, the immediate CO\({}_{2}\) concentration can be utilized as a proper representative for the concentration of aerosol particles, assuming no other substantial CO\({}_{2}\) source exists in the air [11; 18; 19]. Other studies confirmed that the exhaled air from inhalation contains aerosols and also has the potential to bring the SARS-CoV-2 virus where the infected particles floating in the air could be detected for up to 3 h [20; 21]. The risk of airborne transmission of the SARS-CoV-2 virus also occurs significantly in an indoor environment with poor ventilation or without a ventilation system. Therefore, it is critical to keep the concentration of aerosol particles as low as possible to reduce the danger of SARS-CoV-2 virus infection, especially during the COVID-19 pandemic, as presented in an aerosol infection model in [22]. Moreover, the authors in [11] presented that indoor CO\({}_{2}\) concentration is a good indicator for SARS-CoV-2 transmission risk and can be examined easily and immediately using an IAQ sensor. The sensor measurement results are useful for indoor CO\({}_{2}\) monitoring and SARS-CoV-2 transmission risk assessment where several room occupants spend their daily time indoors.