The Control of Metabolic CO2 in Public Transport as a Strategy to Reduce the Transmission of Respiratory Infectious Diseases

Abstract

The global acceptance of the SARS-CoV-2 airborne transmission led to prevention measures based on quality control and air renewal. Among them, carbon dioxide (CO2) measurement has positioned itself as a cost-efficiency, reliable, and straightforward method to assess indoor air renewal indirectly. Through the control of CO2, it is possible to implement and validate the effectiveness of prevention measures to reduce the risk of contagion of respiratory diseases by aerosols. Thanks to the method scalability, CO2 measurement has become the gold standard for diagnosing air quality in shared spaces. Even though collective transport is considered one of the environments with the highest rate of COVID-19 propagation, little research has been done where the air inside vehicles is analyzed. This work explores the generation and accumulation of metabolic CO2 in a tramway (Zaragoza, Spain) operation. Importantly, we propose to use the indicator ppm/person as a basis for comparing environments under different conditions. Our study concludes with an experimental evaluation of the benefit of modifying some parameters of the Heating–Ventilation–Air conditioning (HVAC) system. The study of the particle retention efficiency of the implemented filters shows a poor air cleaning performance that, at present, can be counteracted by opening windows. Seeking a post-pandemic scenario, it will be crucial to seek strategies to improve air quality in public transport to prevent the transmission of infectious diseases.

Development and validation of a methodology to measure exhaled carbon dioxide (CO2) and control indoor air renewal

“…Knowing the activity and the number of occupants is essential to interpret the CO 2 measurements. Determining the ppm/person ratio can be helpful, as we proposed in previous work (see 61 ). This value incorporates the occupancy variable and allows a more precise definition of the efficiency of air renewal, although it assumes homogeneity in exhalation between individuals.…”

“…Many countries have implemented CO2 measurement as a standard in different spaces, such as shopping centers, 57 collective transport, [58][59][60][61] workspaces, 62 or university and school classrooms. [62][63][64][65][66][67] Beyond research projects, some governments have decided to bet on scientific criteria and invest resources to mitigate contagion among the population.…”

Respiratory infection transmission risk and indoor air quality at outpatient departments and emergency treatment units of Sri Lankan teaching hospitals

“…Indoor CO2 concentration has been used as a proxy of the degree of ventilation and, by extension, as an indicator of the risk of contracting respiratory infections in that space [ 5 , 8 – 11 , 37 ]. Based on available literature that we mentioned in the introduction and in discussion we are convinced that the concept is valid [ 5 , 8 – 11 , 37 , 40 , 48 ]. Thus we did not attempt to prove that concept again in this study.…”

“…COVID-19 pandemic and the availability of non-dispersive infrared (NDIR) sensor based relatively cheap but accurate CO 2 monitors have increased the interest and the possibility of wider usage of indoor CO 2 concentration as a proxy of the risk of contracting respiratory infections lately [ 8 – 11 ]. Aerosol dispersion in an indoor space is influenced by its geometry and weather parameters [ 14 ].…”

Estimating Indoor Pollutant Loss Using Mass Balances and Unsupervised Clustering to Recognize Decays

“…In particular, infrared CO 2 sensors and optical particular counters (OPC) are ubiquitously deployed in various indoor environments and heating, ventilation, and air-conditioning (HVAC) systems. Indoor CO 2 concentration is often considered a proxy for ventilation and IAQ and has been linked with inhalation exposure, , cognitive tasks, , and transmission of infectious disease, , while particulate matter (PM) has known health consequences. , However, although most low-cost IAQ sensors show acceptable relative precision, they often suffer from poor absolute accuracy and drift issues . These drawbacks severely limit the application of low-cost sensors in IAQ assessment, exposure monitoring, and building certification.…”