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Author: Veress Árpád · Explosion-protection expertDaily Ex - 12 September 2026
Compliance developments show what is changing; incident reports show where plants actually fail. Optical radiation equipment has entered the ATEX harmonised list, which makes a new fibre link or sensor a possible MoC trigger rather than just instrumentation. Three CSB investigations then supply the harder lessons: an informal procedure at Clairton, isolation work before a turnaround at Martinez, and the wrong flange opened at Deer Park. Each traces back to the same break in the operational chain, from requirement through identification and ownership to verification and evidence.
What changed + what happened + what Operations should do
Today’s edition combines current Ex compliance developments with real incident learning.
1. Current compliance: optical Ex has entered the updated ATEX harmonised list
The EU formally added EN IEC 60079-28:2026 to the ATEX harmonised standards framework on 4 September 2026, covering equipment and transmission systems using optical radiation. The old 2015 reference remains in transition until 4 March 2028.
Why it matters: optical systems can become ignition-relevant even though they are often treated as “just instrumentation” or “just fibre”.
Operational Ex comment:
A new optical sensor, fibre link or measurement system in a hazardous area should be treated as a potential MoC trigger.
Change → Ex suitability review → certificate basis → installation check → documentation → return to service
2. Incident: U.S. Steel Clairton - an informal procedure ended in a fatal gas explosion
The CSB’s August 2026 final report on the U.S. Steel Clairton Coke Works explosion found that toxic, flammable coke-oven gas was released and exploded, killing two people and injuring 11. The CSB identified an ad hoc informal procedure, poor facility siting and ineffective process-safety management among the key issues.
Operational Ex comment:
This is an unfortunate example of where “experienced people know how to do it” is not enough.
For abnormal work involving flammable gas:
task definition → written method → isolation/purging → permit → competence → supervision → verification
The question for the Head of Operations:
Which hazardous tasks in our plant are still controlled mainly by habit rather than by a defined process?
3. Current compliance: the ATEX harmonised list itself is a moving document
The European Commission’s ATEX page now shows multiple amendments during 2026, including January, May and September updates.
Why this matters: “ATEX compliant” is not a fixed statement forever. The technical and legal basis around harmonised standards keeps evolving.
Operational Ex comment:
Do not react to every standards update with replacement.
Use: new requirement → impact review → affected equipment/process → significance → priority
The important thing is to know whether the change matters operationally.
4. Incident/use case: PBF Martinez refinery - isolation work went wrong before turnaround
A CSB incident report describes a February 2025 explosion and fire at the Martinez refinery in California, causing about $924 million in property damage. Contract workers were preparing for turnaround maintenance and installing an isolation blind when the incident occurred.
Operational Ex comment:
Turnaround and maintenance work are among the moments when the normal safe operating model is intentionally disturbed.
That means: positive equipment identification → isolation → depressurisation → gas-free verification → permit → contractor briefing → independent check
should be treated as operational barriers.
5. Incident/use case: PEMEX Deer Park - the wrong equipment was opened
At the PEMEX Deer Park refinery, contract workers opened the wrong flange during maintenance in October 2024. Around 27,000 lb of hydrogen sulfide were released; two contract workers died and 13 people were hospitalized. The CSB’s 2026 report highlighted positive equipment identification, work permitting, contractor management and conduct of operations.
Operational Ex comment: correct permit is useless if it is applied to the wrong equipment.
The minimum chain should be:
correct asset → correct isolation → correct permit → correct person → correct verification
Today’s Operational Ex takeaway
Current compliance tells us what expectations are changing. Incidents tell us where real plants actually fail.
It is because the operational chain broke: requirement → identification → ownership → execution → verification → evidence