Fallacies in criticisms of the J-value

Philip Thomas*, Ian Waddington

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Detailed examination of the criticisms of the J-value put forward by Jones-Lee and Chilton shows their points to be without merit. However, the exercise of refuting their critique has brought out a number of J-value implications of potential interest and value to engineering professionals seeking to find the objectively reasonable amount that ought to be spent on a safety system. The paper applies the J-value to the example of a long-term protection system on a notional major-hazard process plant, where a severe accident would otherwise pose a risk of death to the general public either immediately or in the short term. Equations are developed for the improvement in life expectancy produced by averting such an industrial hazard over a prolonged period. The opportunity is taken to review the developments in the J-value that have taken place over the 12 years since the first paper on the method appeared in Process Safety and Environmental Protection.
Original languageEnglish
Pages (from-to)309-328
Number of pages20
JournalProcess Safety and Environmental Protection
Early online date30 Apr 2019
Publication statusPublished - 1 Jun 2019


  • J-value
  • Risk
  • Immediate hazard
  • VPF
  • Safety
  • Safety fallacies


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