The Safety Critical Systems Handbook, 4th Edition

Chapter 1

The Meaning and Context of Safety Integrity Targets

Abstract

There is no such thing as zero risk. This is because no physical item has zero failure rate, no human being makes zero errors, and no piece of software design can foresee every operational possibility.

Nevertheless public perception of risk, particularly in the aftermath of a major incident, often calls for the zero risk ideal. However, in general, most people understand that this is not practicable, as can be seen from everyday risk of death from various causes. Therefore the concept of defining and accepting a tolerable risk for any particular activity prevails.

Keywords

ALARP; Failure rate; HAZOP; Quantified targets; SIL

1.1. Risk and the Need for Safety Targets

There is no such ...