The death of a father following an explosion at a chemical factory was an "accident", a jury inquest has concluded.
Contractor Robert Cranston was carrying out maintenance on a tank at Briar Chemicals, Norwich, in July 2018 when he suffered serious injuries and thermal burns in an explosion.
The 46-year-old was taken to Norfolk and Norwich University Hospital, but died later that day from head and chest injuries.
Following an 11-day inquest, Yvonne Blake, area coroner for Norfolk, offered the jury a conclusion of "accidental death" - the only finding she deemed appropriate by law.
And it was a conclusion the jury agreed to on Tuesday afternoon as proceedings came to a close.
Over the course of the inquest at Norfolk Coroner's Court, members of the jury heard Mr Cranston had been working at the Briar factory for pipework and fabrication firm Pruce Newman.
The keen sportsman, who lived with his family at Birkbeck Road, Norwich, was tasked with fixing a tank used to hold chemicals.
Among colleagues working alongside him was one of his two sons, Owen, who had begun an apprenticeship with Pruce Newman just a few weeks prior and was at ground level providing "fire watch"
Mr Cranston was on a raised platform and using a grinder to perform welding on the vessel when the explosion occurred.
Earlier on during the inquest, Owen described there being "a bang and a ball of flames", before rushing to break the glass at an alarm point.
He added: “When I ran back to the vessel I could see dad’s welding mask on the ground. At first I thought he had got clear but, as I got close, I could see there was blood running down his face".
Mr Cranston was not responding to any communication from colleagues and was "clearly focused" on trying to breathe, the jury heard.
He was checked over by the site nurse and subsequently by paramedics, before being taken to hospital.
A subsequent investigation by the Health and Safety Executive (HSE) found flying sparks from Mr Cranston's grinder had likely come into contact with Toluene, a highly flammable chemical used in paint thinners and the explosive, TNT.
Toluene had previously passed through the tank, but it had been emptied. It is thought two leaking valves meant around 160 litres of the gas had escaped into pipework.
A resulting HSE report said there had been "some gas vapour directly around the vessel which ignited while 'hot works' were ongoing", thus causing the blast.
The jury heard throughout the inquest that Mr Cranston would not have expected there to be any explosive material in the tank.
On Monday, evidence was given surrounding Briar Chemicals' use of gas monitors, and the fact equipment used before the incident was unsuitable for detecting Toluene.
Ms Blake said: "It seems odd for a chemical company - that has a huge list of safety requirements - to not say to gas monitor suppliers 'these are the gases we need to test for to keep our operations safe'."
Briar's quality, health, safety and environment manager, Mark Smith, responded: "We did not comprehend that a flammable gas detector was better at detecting some gases than others."
The company now uses two types of flammable gas monitors - one of which is "much more sensitive", according to Mr Smith.
As a matter of law, coroner Yvonne Blake said she could only leave the jury with one possible conclusion to consider - that of accidental death.
The burden of proof to reach this conclusion is on the balance of probabilities.
"This is not a case of unlawful killing," added Ms Blake.
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