# Development of Far-UVC-Based Surface Disinfection Prototype for Public Buses
## 1 Introduction  
The outbreak of the COVID-19 pandemic has brought public health and safety to the forefront of global concerns. The rapid transmission of the SARS-CoV-2 virus, which causes COVID-19, has underscored the importance of implementing effective measures to prevent and control the spread of infectious diseases. Among the various settings that require attention, public transport systems have emerged as potential hotspots for viral transmission due to the close proximity of passengers and frequent contact with shared surfaces. In recent years, there has been a growing body of research exploring various aspects of the surface and airborne transmission of viral pathogens including SARS-CoV-2 in public transport. [PERSON] et al. conducted a study tracing surface and airborne SARS-CoV-2 RNA inside public buses and subway trains [1]. The study collected 99 samples from inside Barcelona buses and subway trains. The results showed that the presence of viral RNA fragments in buses was higher than in trains, and relatively higher concentrations of viral RNA fragments were found on support bars than in ambient air inside the vehicles. Public transportation systems can reduce the transmission of SARS-CoV-2 by implementing specific mitigation solutions such as the appropriate filtration of recirculated air and simultaneous use of FFP2 masks, especially in long-distance buses [2]. For urban buses, the maximum occupancy needs to be reduced to maintain a reproductive number of less than 1. However, it is very difficult to achieve such measures in highly populated areas. In response to this unprecedented challenge, innovative technologies have been developed to enhance disinfection protocols within public transport environments. Ultraviolet (UV) light-based systems, known for their ability to rapidly eliminate harmful microorganisms, have gained significant attention as promising solutions. Specifically, the use of UVC light at a wavelength of 222 nanometers (nm) has demonstrated efficient pathogeninactivation while minimizing risks to human health [3; 4; 5; 6; 7]. According to a review on UVC disinfection [8], UVC-based technologies offer several advantages compared to traditional chemical-based disinfection approaches. They are environmentally friendly, have high levels of pathogen reduction (higher than 99.9%), and reduce the manual cleaning and equipment maintenance provided by manpower, which make them very suitable for the disinfection of public transport systems. Another study [9] proved the effectiveness of UV light in inactivating SARS-CoV-2, the virus responsible for COVID-19, in human saliva. The study compared the efficacy of a commercial filtered krypton chlorine (KrCl) excimer light source emitting a peak wavelength of 222 nm to that of a conventional germicidal lamp emitting UV 254 nm. The results showed that both UV wavelengths could effectively reduce the viral load, but the UV 254 nm had a greater capacity to inactivate the virus. The systematic review by [PERSON] et al. [10] assessed the effectiveness and safety of UVC sterilization in reducing nosocomial infections in hospitals. After analyzing 17 eligible studies from 2010 to 2020, positive results were observed when UVC irradiation was used alongside existing cleaning protocols. UVC demonstrated potent germicidal effects against viruses, Methicillin-resistant _Staphylococcus aureus_ (MRSA), and Vancomycin-resistant _Entefrocacci_ (VRE). UVC Disinfection Robots have gained prominence for their ability to employ UVC light, which possesses germicidal properties, to disinfect surfaces and air, offering automated and precise disinfection capabilities in various settings including hospitals, public spaces, and transportation systems [11; 12; 13]. By emitting a specific wavelength of UVC light, these robots can penetrate the DNA of viruses and bacteria, rendering them inactive and incapable of reproduction. This technology has proven particularly effective in hospitals, laboratories, and public spaces, where comprehensive disinfection is vital.