SafeWork NSW is investigating an incident that occurred in South Windsor where a worker was welding on top of a vat when a flash over occurred.
The man was reportedly thrown approximately 5-10 metres across the floor.
The incident happened on Wednesday.
He was taken to hospital with severe burns to the lower body.
Early this year, SafeWork NSW issued a safety alert reminding workplaces of the precautions required when carrying out hot work, for example grinding, welding, oxy cutting or other processes which produce a flame or other ignition source.
According to SafeWork NSW, serious or fatal injuries can occur when hot works are undertaken on or in close proximity to flammable or combustible materials/ substances without appropriate control measures.
Prior to carrying out any hot work on site, it is essential to implement a hot work permit system, which includes a detailed review, to identify all potential hazards associated with the proposed hot work activity and to eliminate the hazards or, where this is not reasonably practicable, control the resulting risks.