The Eastern Daily Press reported that 56-year-old Barry Joy and 28-year-old Daniel Timbers had been working at Harford Attachments' new factory on Spar Road in Norwich when the paint booth they were working in exploded and turned into a fireball.
The Health and Safety Executive (HSE) investigation found the two workers had already sprayed several welded steel buckets on the morning of 13 July 2015 and were preparing for their next batch when the incident happened.
The HSE found that Harford Attachments, which makes couplers and digger buckets for excavators, had not risk-assessed the activities in the confined space. The company's "inconsistent and incomplete approach" to safety management resulted in a lack of suitable control measures, specifically, a suitable and sufficient safe system of work.
Prosecuting, Jonathan Ashley-Norman, told Norwich Crown Court the accident was caused by the workers discharging paint into a 200-litre drum inside the booth, which had been purchased from the Royal Air Force for the new factory.
"The consequences of these actions were that the drum effectively became a bomb, because it held within it flammable paint and thinners, but also vapours being given off which were highly flammable," he said.
"This action caused vapour to enter the paint booth, and consequently came into touch with one of a large number of potential sources of ignition, and, consequently, and foreseeably, exploded."
Ashley-Norman told the court that the manufacturer had previously been warned that it had failed to provide a risk assessment for the spray paint work in the booth.
Ben Compton QC offered a "complete apology" to the workers' families on behalf of the company. He asked for a "lenient" fine as Harford Attachments had been through financial hardship since the incident, and still employs 40 staff.
The Eastern Daily Press reported that Compton had told the court that while the new factory on Spar Road was being commissioned, the safety of the spray booth "dropped off the radar".
"There was no one really in charge of health and safety with the expertise to deal with a very specialist piece of kit," he said. "There was no one person holding the reins saying this must be done before any people go into that booth."
Sentencing Judge Stephen Holt said: "It is ironic the purpose of these new premises was to provide a far better and safer workplace. It is clear no risk assessment had been carried out for the method of cleaning. It would have revealed the dangers that were clearly there."
Harford Attachments pleaded guilty to breaching s 2(1) of the Health and Safety at Work Act and breaching reg 6(4)(f)(i) of the Dangerous Substances and Explosive Atmosphere Regulations 2002. The firm has seven years to pay off the £145,000 fine imposed, with court costs of £65,900.
After sentencing, Steve Kidd, managing director of Harford Attachments, said "many substantial changes have been made so to ensure safe working systems and practices".