SP Plastics, in Baswich, Stafford, went up in flames on October 30, 2014, with more than 50 firefighters tackling the blaze.
Father-of-one Simon Hillier, aged 41, from Hednesford, had been helping out at the business on the day but never came out alive.
Father-of-three Stewart Staples, aged 57, also from Hednesford, was a customer and also died in the blaze.
Now, after a lengthy investigation by Staffordshire Police and the Crown Prosecution Service, a man, thought to be a director of the firm, has been charged.
Richard Pearson, aged 43, from Holyrood Close in Stafford, faces two counts of manslaughter. He is accused of unlawfully killing both men by gross negligence in that he owed a duty of care for the storage and handling of fireworks at unit 7 Tilcon Avenue.
A spokeswoman from Cannock Magistrates Court confirmed the charges and said Pearson was set to appear there on Wednesday morning.
Last year Lynn and Thomas Hillier, parents of Simon, who was an England kickboxing champion from Featherstone Kickboxing Club, told the Express & Star their wait for answers had been ‘absolute hell’.
Mrs Hillier said at the time: “We’ll never get closure I don’t think.
“But it is very important we get answers as to what happened. We still don’t know anything. We probably will never know. It has been very frustrating.”
Mr Hillier added: “We still can’t get the gist of what happened. We haven’t even got a death certificate yet. We just can’t believe he didn’t get out. The police were saying he was found three feet from the door.”
Mr Staples was a worker at Staffordshire County Council, described as a devoted family man with a wife, three children and a young grandson.
He lived in Bond Way and had worked for Staffordshire County Council Highways Department for 26 years. He was also a keen golfer and Walsall FC fan.
Flames at the factory raged on for hours while a police cordon remained around the gutted building for several days afterwards. Members of the public were also warned not to use fireworks if they had purchased them from the site.
Within months the company had gone into liquidation while the remains of the wreckage have long since been demolished.
Inquests have never been held on the victims due to the ongoing criminal investigation. The police passed an initial file to the Crown Prosecution Service in August 2015 but prosecutors requested further evidence.
Staffordshire Police previously said the ‘total destruction’ of the premises and the number of witnesses and experts consulted had led to a ‘lengthy’ and ‘complicated’ inquiry.