The following non-comprehensive list gives advice on how SILs should not be used.
l SILs should be assigned only after a risk analysis. It is meaningless to assign SILs prior to completing such an analysis;
l SILs shall not be used for non-functional safety, e.g. applying SILs to safety against slips, trips and falls;
l Assigning SILs without having defined appropriate measures and techniques for each level is meaningless. In EN 50126 standard only measures and techniques for electronic subsystems have been defined (see EN 50126-4 and EN 50126-5). Therefore, if a safety integrity level is assigned to a mechanic or mechatronic equipment then this is to be considered not applicable and in the demonstration process this has to be stated;
l SIL refers to doing things right, not doing the right thing. Fulfilling all quantitative and qualitative integrity requirements does not guarantee that the related function is correctly defined;
l SILs should not be used for describing systems attributes, e.g. “This is a SIL 4 computer”. The correct wording would be: “This is a computer used to perform a SIL 4 safety-related function”.