A contractor plunged to his death outside the very plant where an inquiry was being held into 10 other fatalities.
Fifteen workers have died at Sasol sites in the past year, and the Solidarity trade union has called the situation a national crisis.
The union is due to petition parliament on Thursday in a bid to root out unsafe practices at industrial plants.
"One person's death is tragic, but the spate of fatal incidents at Sasol plants during the past year is cause for serious alarm," Solidarity spokesperson Dirk Hermann said.
The contractor, who cannot be identified until his family have been notified, fell off scaffolding at Sasol's plant in Secunda on Monday.
Sasol spokesperson Johann van Rheede said Monday's incident was being investigated, and Labour Minister Membathisi Mdladlana said a team of inspectors from the department of labour would be conducting their own probe.
The accident followed fires at two Sasol plants last week, in which four people sustained mild injuries, and a blast on September 1, in which 10 people were killed and 369 injured.
Jaco Kleynhans of Solidarity is furious and is going to parliament to petition MPs to ratify an International Labour Organisation (ILO) convention in a bid to stop such accidents.
"This is a national crisis," Kleynhans warned.
Van Rheede said Sasol had taken steps to launch a safety charter between itself and the unions, and had appointed DuPont, an external company, to conduct a safety review of the corporation.
"Safety in Sasol is our top priority - and we've been open about it."
The DuPont report, released on May 25, three days before the fire at Sasol's Secunda plant, accuses management of not being visible.
DuPont said Sasol's commitment to safety could be improved if managers spent more time on the operations, and called for supervisors, employees and contractors to be given further safety training.
During the hearing into the causes of the September blast, Solidarity accused Sasol of failing to comply with standards set by the ILO.
However, Sasol pointed out that South Africa had not ratified ILO's Prevention of Major Industrial Accidents Convention, which meant it was not bound by it.
Kleynhans said this was why he was on his way to parliament.
Meanwhile, South African Chemical Workers Union spokesperson Palatsi Palatsi claimed contractors were not given adequate safety training, which was leading to accidents.
"I'd be lying if I said Sasol was doing nothing, but I think the company still needs improving so that the number of accidents can be minimised."
Accidents since 2004