How to Verify the Integrity of Protectives Functions Falling Under the Scope of ATEX 94-9?

The border between protective functions according to the ATEX 94/9 directive and safety instrumented functions as classically implemented in the process industries is not always evident. For a function falling under the ATEX 94/9 scope, clear requirements regarding conformity assessment procedures of the concerned components are stated in the Directive and have to be followed. Requirements of the Directive are mainly deterministic and do not let much space for complex or programmable electronics. For functions considered as relevant for the safeguarding of industrial process plants, the only requirement is to use "state of the art" which is considered as being achieved if the realisation of this function is in accordance with published standards like IEC/EN 61508/61511. Problems arise if the so validated function is also falling under the ATEX 94/9 scope... This paper deal with different options and problems which are encountered by achieving the migration between ATEX requirements and functional safety standards.