Highly flammable gas went undetected prior to the blast which killed a father as he carried out maintenance work, an inquest has heard.

Contractor Robert Cranston was working on a tank at Briar Chemicals, Norwich, in July 2018 when he suffered serious injuries and thermal burns in an explosion.

Eastern Daily Press: The Briar Chemicals plant on Sweet Briar Road, NorwichThe Briar Chemicals plant on Sweet Briar Road, Norwich (Image: Copypright Mike Page, All Rights Reserved Before any use is made of this picture, including dispaly, publication, broadcast,...)

The blast was witnessed by one of his two sons, Owen, who had started working as an apprentice at the plant just months prior.

Following the incident, Mr Cranston was taken to the Norfolk and Norwich University Hospital, but died later that day aged 46.

The keen sportsman, who was working at the Briar factory for pipework and fabrication firm, Pruce Newman, had been welding when the explosion occurred.

Eastern Daily Press: Robert Cranston pictured with his sons Lewis (left) and Owen. Mr Cranston died following an explosion at Briar Chemicals in NorwichRobert Cranston pictured with his sons Lewis (left) and Owen. Mr Cranston died following an explosion at Briar Chemicals in Norwich (Image: Archant)

Flying sparks came into contact with Toluene, a highly flammable chemical used in paint thinners and TNT.

An inquest into his death, held at Norfolk Coroner's Court, previously heard Mr Cranston would not have expected there to any explosive material in the tank.

Having been adjourned for three weeks, proceedings resumed on Monday, when the jury heard evidence from Briar's quality, health, safety and environment manager Mark Smith.

He was questioned by area coroner for Norfolk, Yvonne Blake, on why gas monitoring equipment on the tank was not suitable for detecting Toluene.

She 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'."

Mr Smith responded: "We did not comprehend that a flammable gas detector was, in fact, better at detecting some gases than others."

Eastern Daily Press: Robert Cranston pictured with his wife, Claire. Mr Cranston died following an explosion at Briar Chemicals in NorwichRobert Cranston pictured with his wife, Claire. Mr Cranston died following an explosion at Briar Chemicals in Norwich (Image: Archant)

Failure to perform proper checks demonstrated a "complete lack of professional curiosity", added Ms Blake.

Mr Smith said the issue had not been raised in 25 Health and Safety Executive (HSE) audits between 2012 and 2018. It has since been highlighted by the HSE as part of its investigation into Mr Cranston's death.

Briar Chemicals now uses two types of flammable gas monitors - one of which is "much more sensitive", according to Mr Smith.

He said: "We cannot change what happened, but perhaps we can do something to make sure this does not happen elsewhere."

The jury will return on Tuesday to provide its conclusion.