The $1.09 million in works required by the Resources Regulator - including $210,000 to Muswellbrook Rural Fire Service - is the highest to date in NSW and is more than double a $500,000 fine imposed by a court on another NSW mine following a serious worker injury case.

The enforceable undertaking allowed the Muswellbrook mine to avoid making an admission of guilt, but included acknowledgment "its alleged failure to meet a health and safety duty exposed a worker to a risk of death or serious injury", Resources Regulator executive director Anthony Keon said.

The regulator has launched separate criminal proceedings against contractor Otraco International, owned by Downer EDl, for an alleged breach of the Work Health and Safety Act for the same incident.

It took just 19 seconds for the 29-year-old Mount Arthur contract worker to be covered in diesel fuel and running for his life with part of his body alight as black smoke poured from flames in a refuelling area on August 10, 2017.

An investigation report found the worker selected an 800 litres per minute adapter rather than a 300 litre one while refuelling a tyre handling machine because the fittings were the same colour and poorly labelled.

Within seconds the fuel nozzle was ejected and "flung around under pressure", with diesel fuel flowing at a peak of 791 litres per minute after 18 seconds, before a "flame flashed back towards the worker" after diesel came in contact with engine parts estimated to be more than 300 degrees Celsius.

The worker ran for his life towards a drain where mud extinguished flames from his head and clothes. He suffered serious burns to the face, neck, torso and arms.

An investigation report criticised Mount Arthur coal mine and contractor, Otraco International owned by Downer EDI, for leaving contract tyre handlers at risk by failing to establish safe refuelling procedures.

The investigation identified the use of petrol adapters since 1995 which were not fit for purpose.

"The fact that the adapter was kept at the mine for such a long time demonstrates that there was a deficiency in the (mine's) inspection regime for the refuelling facility," the investigation report said.

Mr Keon said while Mount Arthur Coal was not the worker's direct employer "it still had a significant duty of care, one that was not abrogated by the use of a contractor".

Under the enforceable undertaking Mount Arthur must spend nearly $800,000 upgrading refuelling areas at the mine site, in addition to an estimated $960,000 it has already spent on upgrades following the incident, $210,000 to the RFS, more than $77,000 for the Resources Regulator's costs and place advertisements in the Newcastle Herald and Muswellbrook Chronicle about the terms of the undertaking.

Chief investigator Steve Orr said the highest value mining work health and safety undertaking accepted in NSW to date would deliver "significant engineering improvements at the mine, industry training and vital monetary support for the region's Rural Fire Service".

"The Regulator accepted the Enforceable Undertaking as it will deliver tangible benefits to the workforce and community that could not be achieved through prosecution action alone," Mr Orr said.

Lessons from the investigation had been shared widely with the mining industry using digital animations to demonstrate how the incident happened.

"These animations are the first of their kind to be developed by a work health and safety regulator anywhere in Australia and are aimed at helping the industry address safety issues," Mr Orr said.