I was introduced to What Went Wrong? by Trevor Kletz by one of my former bosses. Every now and then, I like to reread it to remind myself of the author’s timeless message, which was also his primary mission:
“Prevent the industry from forgetting its lessons.”
First published decades ago and now in its fifth edition, ***What Went Wrong?***remained one of the most influential books ever written on process safety. It was a collection of real industrial accidents, analysed not to assign blame but to teach, and to ensure that hard-won knowledge was not lost between generations.
Kletz, a chemical engineer who worked for ICI for many years, wrote this book after realising a painful truth: organisations had no memory. People retired, changed jobs, or moved on, and with them went the stories that once kept others safe. His mission was to make those stories unforgettable.
Below is a short summary of the book, structured around its two parts. I hope some of you find it useful, whether to learn, reflect, or share as a safety conversation in your team.
Part 1 – What Went Wrong? (Technical Lessons We Kept Forgetting)
The first half of the book explored the technical and operational causes of accidents, the kind that appeared in incident reports yet continued to recur in every generation of engineers.
It began where many tragedies began: maintenance.
Inadequate isolation, poor labelling, or incomplete permits had turned ordinary maintenance jobs into fatal ones. Kletz reminded readers that maintenance preparation was one of the most dangerous operations in any plant.
He then discussed modifications, those “temporary” or “small” changes that no one bothered to document properly. From Flixborough to modern-day sites, disasters had often started with the phrase, “It is just a quick fix.” Kletz advocated for structured Management of Change systems. Every modification, however small, needed to be assessed, documented, and authorised. Every company had an MOC system, but it needed to be practical and effective rather than bureaucratic.
He also reframed human error, not as carelessness but as design failure. Humans forgot, misunderstood, or violated rules, so systems had to be built to anticipate that.
“A safe system,” he writes, “makes it difficult to do the wrong things and easy to do the right ones.”
The chapters that followed deal with familiar but often overlooked culprits:
- Leaks that started small but end catastrophically.
- Fires and explosions triggered by poor isolation or purging practices.
- Blocked relief valves, corrosion, and poor workmanship that quietly eroded safety.
Each example reinforced one theme: technical excellence was not enough without discipline. Valves needed to be labelled, isolations verified, and assumptions questioned. The simplest habits were often what stood between control and catastrophe.
By the end of Part 1, Kletz’s point was unmistakable:
We don’t have “new” accidents, only old lessons unlearned.
Part 2 – Still Going Wrong (The Human and Organizational Lessons)
In the second half, the author turned the mirror toward people and organisations. The focus shifted from equipment to culture, from “how the plant failed” to “why the people forgot.”
He revisited earlier topics, maintenance, permits, confined spaces, but this time asked a deeper question:
Why do accidents repeat when procedures already exist?
His answer: **because the rules are treated as obstacles, not obligations.**He showed how housekeeping and plant tidiness revealed much about culture. A messy plant often hid neglected safety. He warned that when experienced staff left without proper knowledge transfer, the organisation’s “safety memory” disappeared with them.
Training, Kletz said, should have been story-based rather than slide-based. People forgot checklists, but they remembered stories of what went wrong and why.
Later chapters introduced ideas that have since become foundations of modern process safety:
- Inherently safer design to eliminate hazards rather than control them.
- Management of Change to formalise every modification, no matter how minor.
- Near-miss learning to treat luck as an unreliable safety barrier.
- Process safety vs. personal safety to avoid confusing “no injuries” with “no risks.”
The final chapters expanded on leadership and memory. Safety, Kletz argued, could not be delegated to paperwork. It depended on managers who listened, asked questions, and reinforced learning through visible actions.
He closed with a haunting truth:
“A high price has been paid for the information in this book — people killed and billions lost.
You get it for the price of a book. Use it well.”
Why It Still Matters
For anyone in oil & gas, chemicals, or heavy industry, What Went Wrong? is more than a book. It’s a reminder that safety is not about compliance or metrics; it’s about memory.
It’s about passing on the lessons so that the next generation doesn’t pay the same price again. In the end, Trevor Kletz’s legacy was not only about preventing accidents, but building organisations that remember.
#ProcessSafety #WhatWentWrong #OilAndGas #Engineering #SafetyCulture #LearningFromFailure #InherentSafety #ManagementOfChange