Many of the victims are being treated at a specialist burn's unit
The injuries suffered by the 13 victims were widespread. Eleven are being treated in the burns unit - seven are critical and five are on life support machines.
Staff at the burn's unit in Morriston Hospital have said that many of the victims will have to undergo weeks of extensive treatment.
Clinical director at Morriston Hospital, Hamish Laing said: "The patients are nearly all going to have to have major surgery and that will involve skin grafting and more technological ways of replacing burnt skin.
"The ones on life support machines are receiving full intensive care.
He added: "The immediate effects of this incident will go on for several days here but the patients, many of them, will be with us for many weeks and therefore it is quite a long process.
"We are fortunate to have one of the leading centres for burns in the United Kingdom based here in Swansea and we provide a service for the majority of Wales here."
This incident is the largest that the unit has had to deal with since it was moved from Chepstow in south east Wales, to Swansea in 1994.
Hospital chiefs have said that it was "fortunate" that the expertise to deal with the situation was so readily on hand.
"We are planning to use some of the most advanced technology with artificial skin to deal with some of these patients and that is quite complicated," Mr Laing added.
"We were able to get all the staff we needed in time and teams of surgeons, anaesthetists, and therapists and nurses are working to look after these patients.
"It was perhaps fortunate that we were so close.
Hot gases There were extensive injuries in addition to severe burns, that had to be dealt with as staff tried to stabilise the injured workers.
"Patients are often thrown considerable distances and so can suffer injuries to broken bones, dislocated shoulders and injuries particularly to the lungs, which can be affected by the blast and also by the hot gases," Mr Laing said.
Hospital staff have said that relatives and patients are being offered full psychological support.
Surgery is currently under way and teams are on standby to work throughout the weekend and next week.