## 5 Conclusions  
We present these results to spread awareness of the consequences of applying the currently available wavelengths of UVC LEDs in disinfecting systems because we have observed their increasing applicability in research and commercial projects. Our discussions with researchers of various specializations since the beginning of the COVID-19 pandemic convinced us that this awareness is not common. Our research aimed to analyze the disinfection reliability of the exemplary latest technological solutions for UV radiation sources. For this purpose, we selected six models of high-power UVC LEDs and analyzed their characterization during a 1500 h degradation test. Based on the results of the measurements, we evaluated the disinfection times of exemplary microorganisms. Therefore, we linked the UVC source's degradation performance with the effectiveness of the disinfection process. This research shows that applying UVC LED technology in disinfection devices requires a careful approach compared to using LP-Hg lamps. If the degradation effects (thermal or time-related) are not carefully investigated and considered during the design of the device or the duration of disinfection is not extended gradually during the device'slifetime, the reliability of disinfection is not assured. Precisely, the delivered doses are not controlled. To conduct an effective disinfection process, it is necessary to know the wavelength of the emission (affecting the germicidal effectiveness) and to control the optical power of the sources after their thermal stabilization. Therefore, for each UVC LED emitter, it is necessary to determine its operating conditions (\(I,T\)) and their impact on the degradation process (decrease in electroluminescence and optical power over time). The prediction of the system efficiency should take into account the gradual reduction in the emitted optical power. Constant or periodic control of the energy parameters of the radiation should be recommended after each device start-up to ensure stable performance characteristics in the disinfection process. The most important operational parameters affecting the degradation rate of UVC LEDs are the operating current and operating temperature. Our research shows that the reliability of long-term disinfection using UVC LEDs is limited if the degradation effects are neglected. Unlike LP-Hg lamps, the degradation of LEDs still requires investigation and analysis, as the variation in the parameters of commercially available UVC LEDs is significant, not commonly known, and depends on many factors, e.g., their construction, the manufacturer, and the quality of the emitter and its operating conditions. One of the leading technical problems is also the availability of manufacturer data, which are more modest when compared to emitters operating in the visible range. The ideal situation would be if manufacturers delivered degradation data on the guaranteed disinfection efficacy based on statistical measurements or at least the expected lifetime evaluated similarly to LP-Hg lamps. However, we can state, beyond any doubt, that when designing disinfection systems based on UVC LEDs, extreme caution should be taken due to their unpredictable degradation, especially in the absence of data to assess the current density of the semiconductor junction. It can also be noticed that when comparing the results of the UVC LED lifetime with the doses required for microorganism deactivation, a disinfection time of a single procedure in laboratory conditions may not be very time-consuming. However, it is converted into a longer disinfection time in actual conditions while maintaining similar irradiance values. Due to a specific area of health safety, it seems reasonable to elaborate dedicated methods, systems, and algorithms to control the emitter operating point over time in order to obtain a stable disinfection efficiency when LED emitters are applied.