## 3 Results
### Evaluation of the Impact of Degradation of UVC LEDs on Their Relative Gernicidal Effectiveness  
To analyze the effect of \(\Delta\)_OP_, \(\Delta\lambda\), and \(\Delta\)_FWHM_, based on the results presented in Figures 4-8, the times required for the deactivation of the selected groups of pathogens were calculated (Equations (4)-(6)) considering different efficiency curves (IESNA, DIN, Gates--Figure 1). Figures 9 and 10 present the results of calculating the relative germicidal effectiveness of the tested LEDs due to the degradation procedure and the increase in the operation temperature, respectively, assuming delivering an equal _OP_ to the disinfected surface from the LP-Hg and all LEDs before degradation. Figure 8: Peak wavelength \(\lambda\) (**a**) and spectral half-width FWHM (**b**) of LEDs before (0 h) and after the procedure of degradation (1500 h) at temperatures of 20 \({}^{\circ}\)C and 60 \({}^{\circ}\)C.  
Figure 9: \(RGE_{LED}\) of UVC LED radiation before and after the degradation process at temperature of 60 \({}^{\circ}\)C related to the \(GE\) obtained by non-degraded LP-Hg lamp; (**a**) decrease in optical power excluded (only effect of time on \(\lambda\) and _FWHM_ included), (**b**) the decrease in optical power included (cumulative effect of time on _OP_, \(\lambda\), and _FWHM_). Comparing the calculated pathogen germicidal efficiencies, \(RGE_{LEDI}\) and \(RGE_{LEDS}\) (Equations (4)-(6)), for the LEDs emitting different wavelengths, LED1 (271 nm) and LED5 (281 nm), relative differences ranging from 32% (IESNA) to 64% (Gates) can be noticed (Figure 9b). It follows that the degradation process significantly impacted the power of the UVC LED radiation and, as a result, the \(RGE\). The effect of the changes in the \(OP\) and spectral parameters of each tested LED on the \(RGE\) after 1500 h of degradation is presented in Figure 9b. During this research, a 20.5-85% decrease in the \(OP\) of each LED can be observed, which caused a 22-85% decrease in their \(RGE\). Based on the above results, analyses were carried out to determine the role of the changes in the spectral parameters in this process (Figure 9a). According to the results of the calculations, the changes in the value of \(\lambda\) and the \(FWHM\) of the tested LEDs due to the degradation while maintaining a constant \(OP\) on the disinfection effectiveness can be considered insignificant. The calculated \(RGE\) values due to the degradation shift in the \(SPD\) varied only within \(\pm\)2%. The results of the calculation of the effect of the increase in the operation temperature on the \(RGE\) are presented in Figure 10. The most significant decrease in the \(RGE\) of 14-16% (depending on the assumed pathogen spectral sensitivity curve \(S_{\text{g}}(\lambda)\)) was observed for LED5 with an increase in the housing temperature from 20 \({}^{\circ}\)C to 60 \({}^{\circ}\)C. The most minor changes in the \(RGE\) were noted for LED4 and LED2 (7-9%). The above changes in the \(RGE\) resulted directly from the difference in their \(OP\) and, to a lesser extent, from the SPD of the radiation. procedure, \(t_{dis}\) extended from 18.5 s to 34.7 s (Figure 12b), and \(t_{dis,average}\) extended from 21 s to 34.6 s (Figure 11b). We also observed the impact of the temperature of operation on the value of \(t_{dis}\). For the low LED housing temperature \(T\) = 20 \({}^{\circ}\)C, \(t_{dis}\) ranged from 16.0 s to 25.3 s (Figure 12a), and the value of \(t_{dis,average}\) ranged from 16.8 s to 23.6 s (Figure 11a). For the higher temperatures (\(T\) = 60 \({}^{\circ}\)C), \(t_{dis}\) ranged from 17.6 s to 30.2 s (Figure 12a), and \(t_{dis,average}\) ranged from 18.4 s to 27.7 s (Figure 11a). Disregarding these changes in the disinfection time means a significant decrease in the reliability of the process and, consequently, insufficient microbiological safety.