It caused the fire to light instantly and quickly spread out of control.
The three people in the second storey unit above were then forced to jump onto mattresses below, after flames blocked the exit, with a woman breaking her ankle in the process.
A 52-year-old was taken to Royal North Shore Hospital with serious burns to her legs.
One resident told 9News he jumped because he didn’t want to die.
“I’ve got kids, I want to see my kids,” the resident said.
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Tyler Boatwright from Fire and Rescue NSW said there were flames three metres out of the side windows.
“Lots of fuel in there to burn it was an extremely hot intense fire,” Boatwright said.
One woman’s cat was pulled from the blaze.
“We did find the cat… and we’ve put it on a ventilator and sent it the vet,” Boatwright said.
Working smoke alarms went off, which saved the lives of the affected residents.