David Chandler, 45, passed away at the plant where he was working as a contracted engineer after being sent in “like a canary down a mine” to carry out repairs. Rescue crews dashed to the scene following the toxic leak and 22 people, including 11 staff, two police officers and nine fire-fighters, were taken to hospital. Mr Chandler was pronounced dead in hospital and a post mortem revealed he died as a result of inhaling ammonia at the factory in Northampton on November 9, 2016. Northamptonshire Coroners Court heard how gas had escaped from a valve in the compressor unit before a “great blue cloud of smoke” exploded in Mr Chandler’s face. The leak happened during work on the compressor - which uses ammonia to chill products used in brewing beer. Karl Hurst, representing Mr Chandler’s family, told the inquest: “Somehow that valve became open. “And somehow the valve beneath it allowed ammonia to escape from it.” He questioned the safety of the operation by comparing the engineers working on the compressor to “a canary down the mine”. Co-worker Clive Bignall said he and a colleague Stuart Wright has been trying to move the compressor using an overhead hoist when the toxic leak occurred. Holding back tears, he told the court: “The ammonia nearly hit me in the face as well. “A cloud of bright blue smoke came straight out this pipe straight into Dave’s face.” He said he had run out of the factory and desperately tried to phone Mr Chandler after the site was evacuated. Mr Bignall also told the jury how their company Speedrite Ltd “would not have been anywhere near” the machine if they knew ammonia was in the pipe. Anthony Warren, a pipe fitter who was working at the factory at the time, told the jury how he first realised something was wrong. He said: “These two men were running towards me. “They were shouting to get out... there was thick cloud behind them.” The inquest was told how the pipe had been “isolated” and emptied at least two years before and was being worked on as part of an energy efficiency project. Coroner Philip Barlow said there was “no dispute” to the fact Mr Chandler died “from the inhalation of ammonia”. He said the questions for the jury sitting at Northampton County Hall, was how that ammonia came to be discharged and how it could have been prevented. David, of Bridgnorth, Shropshire, was married to Laura, 33. They had two daughters, Ava, seven, and four-year-old Isabella. At the time of his death, his family paid tribute and said: “David was a happy person, he always had a smile on his face, was always happy to help others and you would never hear anyone say a bad thing about him. “Not only do Laura, Ava and Isabella have to learn to cope with this, but also David’s two sisters and father who are left devastated and heartbroken.”