## 4 Discussion  
Ambulance vehicles are an integral part of emergency medical services. They can respond to thousands of cases per year and after each mission, each ambulance vehicle must be cleaned and decontaminated to be ready for use for the next mission. The possibility of having increasingly effective cleaning protocols for these environments is essential to limit the presence of pathogenic microorganisms that represent a potential risk of infection for patients and paramedics. Furthermore, an ineffective disinfection of the ambulance and the contamination of patients or transported personnel can contribute to the spread of pathogenic microorganisms in hospital environments and thus contribute to the development of health care. A recent study has shown that the greatest reduction in the risk of acquiring pathogen infections in a hospital setting can be achieved with the use of enhanced environmental disinfection strategies, especially with the addition of a UV-C device to the standard disinfectant strategy [44]. In the present study, an advanced UltraViolet SANitizing System (UV-SAN) has been developed to disinfect ambulance vehicles from dangerous pathogens, like SARS-CoV-2 but also from MDR bacteria. Based on our in vitro results, a smaller dose of UVC (55.8-248 mJ/m\({}^{2}\)) is enough to reduce the SARS-CoV2 viral titer of >99.99% under experimental conditions. In particular, plastic seems to be the most refractory material to UVC disinfection, followed by stainless steel and rubber, where the latter showed the best compliance with the treatment. These results are comparable to those obtained from previous studies where laboratory tests have shown that the UVC susceptibility of virus depends on the type of surface [22; 31; 33]. To evaluate the irradiation times of the UV-SAN system inside the ambulance a calibrated mapping of the irradiance was performed inside the vehicle. This mapping was carried out measuring the irradiance in different points with the same calibrated Reference Sensor D-SiCONORM-LP-REF, as reported in Table 6.  
Once the UVC dose necessary to obtain a log reduction of the virus, (\(D_{log\_n}\)), is known and the irradiance (_Irr_) in a certain point measured, the irradiation time, (\(t_{exp\_log\_n}\)), is calculated with the following equation:  
\[t_{exp\_log\_n}=D_{log\_n}/Irr \tag{1}\] \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{3}{c}{**Surface Characteristics**} & \multicolumn{5}{c}{**Time for Log Reduction [s]**} \\ \hline
**Position** & **Material** & **Irradiance [W/cm\({}^{2}\)]** & **Log1** & **Log2** & **Log3** & **Log4** \\ \hline Instruments shelf & Plastic & 1 & 46 & 88 & 129 & 170 \\ \hline Stretcher base & Metal & 0.45 & 127 & 269 & 410 & 551 \\ \hline Back Door & Plastic & 0.24 & 193 & 365 & 537 & 709 \\ \hline Lateral seat & Plastic & 1 & 46 & 88 & 129 & 170 \\ \hline Seat & Plastic & 0.35 & 132 & 250 & 368 & 486 \\ \hline Floor 1 & Rubber & 0.65 & 12 & 36 & 84 & 132 \\ \hline Headrest & Plastic & 1.27 & 36 & 69 & 101 & 134 \\ \hline Floor 2 & Rubber & 0.65 & 12 & 36 & 84 & 132 \\ \hline Stretcher Armrest (right) & Metal & 0.74 & 77 & 163 & 249 & 335 \\ \hline Stretcher Armrest (left) & Metal & 0.72 & 80 & 168 & 256 & 344 \\ \hline Seat Armrest (right) & Plastic & 0.75 & 62 & 117 & 172 & 227 \\ \hline Seat Armrest (left) & Plastic & 1.34 & 34 & 65 & 96 & 127 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Evaluation of time needed to reduce the SARS-CoV-2 virus over different surfaces in the patient compartment of the ambulance. By applying Equation (1), the time required to obtain a reduction of up to 99.99% was calculated for several points within the ambulance, also taking into account the material, as reported in Table 6.  
The UV-SAN system could be able to achieve a viral reduction equivalent to 99.99% by after about 10 min of irradiation.