Conceptualization of an Air-Extraction System to Mitigate COVID-19 Transmissions Inside Public Transportation Buses

Introduction

The World Health Organization (WHO) in collaboration with the University of Bath (United Kingdom) have developed an air-quality model to collect data from satellite measurements monitored in cities and rural areas from over 3,000 locations. Such model confirms that 92% of the world’s population inhabit in areas that exceed limits established by the organization (WHO, 2020). Exposure to polluted air is related to more than 3 million deaths per year. In addition, humanity suffers from a pandemic derived from a SARS-CoV-2 disease, which produces pneumonia and a severe breathing difficulty syndrome. The current pandemic has generated concern among the world community, Covid-19 is rapidly spreading in many ways and one of them is ventilation and air conditioning systems, which work with air transporting a group of pollutants, virus and bacteria while moving. In the case of public transportation the same phenomenon occurs when people get exposed according to the place and time they use for transportation; if there is a Covid-19 infected person inside the transportation system, he or she will excrete drops of saliva when sneezing, coughing, breathing or talking out loud, and the extension size of such expelled particles is from 1 to 5 mm in an approximate space of 1 to 2 m (Yu. et al., 2004). Droplets excreted by the infected person will become bioaerosols (Adhikari et al., 2019), and the particles have an approximate diameter of 0.3 to 100 μg; in such a way that the breathable fraction of 1 a 10 μg is worrisome (Tindale et al., 2020).

Therefore, bad air quality increases death rates every year (European Environment Agency, 2005). Recent studies show that the atmospheric aerosol contains solid or liquid particles that are suspended in the air of relatively closed spaces. The United States Environmental Protection Agency (EPA) affirms that particle contamination is a combination of solid particles (dirt, dust and smoke) or liquid drops in the air; while human sight only sees a few, others can only be analyzed with an electronic microscope. PM10 particles are formed by thick mode particles (10 micrometers and smaller), while PM2.5 are formed by fine mode particles (2.5 micrometers) (EPA, 2006). According to the Agency, an acceptable PM standard in the atmosphere for short-term health is defined as: (daily average of 24 hours) 35 μg/m ³ for PM2.5 and 150 μg/m ³for PM10. The standards for the World Health Organization (WHO) are set as.5 25 μg/m ³ for PM2 and 150 μg/m ³ for PM10. However, they highlight the fact that even low standards could affect human health (WHO, 2016). This Organization’s statistics show that 4.6 million people die each year due to bad air quality illnesses (Cohen et al., 2017). For ventilation and air conditioning systems in public transportation, the air filter is an important component in order to stop and possibly eliminate Covid-19 particles (Elsaid and Ahmed, 2021). Different public transportation systems address mobility needs; however, buses are the main base in different countries around the world, and along the use of fuel, air filtration of old buses and interior designs as well as ventilation, among others, make a vehicle a high risk place to get Covid-19 if used as a work place or a transportation system.