This paper discusses the principles of tech. reliability and use functional safety and explosion protection of MSR technol. The application of functional safety within the explosion protection, eg. in the form of discrete levels (SIL, PL) for MSR facilities, as well as their formal and computational evidence has been available for some time discussed. A manner and the content of the discussions show that here are some uncertainties regarding the classification, application and expediency of the transfer of functional safety into the explosion protection exist. The following article should contribute to the clarification.