## 3 Results
### Fluid-Dynamic Results  
This model allows for the determination of the transit time for each individual particle within the electromagnetic wave field generated by the E4 Shield device, taking into account the relative probability of virus inactivation in the particle. A sphere with a diameter of 0.5 m, clearly depicted in grey in Figure 10, was used as a reference for the proximity area of the susceptible individual. The experimentally derived deactivation temporal function (reported in Figure 7) exhibits a very fast action. Nonetheless, it was necessary to investigate the fate of the virus-laden particles during the very first minute of emission from the infected individual's mouths. During the first minute, the exposure to the MW field is assumed to deactivate from 10% to 90% of the virus particles. With the Lagrangian model, it was possible to mark a single particle and track its fate, \"measuring\" the time from emission to the moment it enters the 50 cm diameter respiratory sphere. Focusing on the particles that entered the respiratory sphere in the 120 s since their emission, in Figure 11 the distribution of travel times is depicted for the cooling and heating scenarios. It can be observed that the average time to the respiratory volume is close to 60 s and that a non-negligible proportion of the particles reaches the volume in a shorter time period. The deactivation effect after 40 s of exposure to MWs is assumed to be around 60% (40% survival rate). The analysis of Figure 11 is critical to the evaluation of the reduction in the risk of contagion. The Eulerian simulations generated concentration contours of the gas in various regions of the room. A limitation of this approach lies in the homogenous dispersion assumption that correlates gas concentration (solved as a scalar transport in the simulations) to the particle spectral concentration and the viral loads. In fact, only the smallest diameter particles have a diffusion and advection behavior very close to the gas. At a short distance and time after emission, the respiratory jet might generate a different distribution of  
Figure 10: Lagrangian simulation: states corresponding to different moments of the transient in the summer case with mixed system (**a**) at 10 s and (**b**) at 60 s.  
Figure 9: Simulation of E4 Shield device’s E-field in the office: the device was placed on the table between the two individuals. In this figure, the E-field amplitude evaluated in CST @9 GHz is shown: (**a**) view in the xy plane (z = 1 m); (**b**) view in the zx plane (y = 1.5 m). particles than in the case of gas. Nonetheless, the Eulerian approach allows for much longer transient simulations and even steady-state ones, which can be used to analyze the ventilation efficiency of the room. Figure 12 shows the strong deflection effect of the thermal plume of the emitter individual due to the motion field imposed by the air diffuser. Table 5 reports the gas concentrations in the proximity of the two susceptible individuals with and without the E4 Shield device (in both placements). Although using gas as a proxy is appropriate for respiratory particles with diameters below 5 microns, it should be noted that the particles analyzed in this study were considered to be up to 800 microns in diameter. This assumption does not contradict the use of gas as a proxy for respiratory particles. More than 94% of the particles had diameters less than 5 microns, while the remaining particles quickly fall to the ground due to gravity. These larger particles do not become suspended in the air and therefore do not contribute to the risk of infection [29; 38; 40; 41]. Figure 11: Distribution of particles travel times from the mouth to the respiratory sphere.