"Common cause information indicates that a pressurised container exploded near where the men were working, said Netcare 911 spokesperson Jeff Wicks.
"The explosion sent a fragment of the container flying through the air, striking one of the workers in the face."
Paramedics arrived to find the man in a critical condition.
He sustained severe facial trauma, inhalation burns and second degree burns to his back, said Wicks.
His co-workers sustained minor burn wounds, he said.
They were all were stabilised at the scene and taken to a nearby hospital for further treatment.