Authorities say a welding mishap is believed to have sparked a fire inside a West Wollongong home on Thursday.
Emergency services - including multiple Fire and Rescue NSW (FRNSW) trucks, police and paramedics - rushed to the scene after a fire broke out in the two-storey home about 10am.
Renovations were being carried out at the property, on the corner of Robsons Road and Parsons Street, at the time.
It is believed two men, aged 43 and 48, were welding a beam, when the fire started. Two boys, aged 13 and 15, were also home.
NSW Ambulance special operations paramedic Oliver Aleman said all escaped serious injuries.
"The dad said the smoke detector actually alerted him to what was going on and he managed to get his children out of the house," Mr Aleman said.
"There were four people in the house and they all came out quite unscathed, [some] slight smoke irritation but they are in a stable condition.
"They were quite upset about the fact the house caught alight and they had to run out to save their lives."
Peter McNamara was driving home along Robsons Road when he saw "a big plume of smoke" and alerted authorities.
"I just pulled across straight away, I thought it must have been somebody burning off or something but suddenly I could see it [coming] from the house," the 61-year-old, from Figtree, told the Mercury.
"I was the first here and I just rang the fire brigade. Everyone was panicking.
"It just happened so fast, that was the amazing thing.
"There were kids and people running everywhere around here to try and turn things off and salvage things ... just the speed of it and before we knew where we were [there were] big flames coming out the window.
"The fire brigade came pretty quickly."
Mr McNamara said he'd spoken with the home's owner, who told him he'd been doing a number of renovations.
"I checked with the owners to make sure that no one was inside and they said there wasn't anyone inside," he said.
"We also went around the back to make sure there wasn't any people hanging around the back there, in case they could get trapped."
FRNSW Illawarra duty commander Inspector Jay Bland said firefighters arrived to find the house "fully involved in fire".
"Fire crews immediately got to work to undertake a search-and-rescue operation, as well as fire attack," Insp Bland said.
"At the conclusion of the search and rescue, no persons were found or reported missing and as such we were able to continue our fire attack operations."
The house sustained significant damage to its second level, he said.
The fire was contained to the area of origin, with crews also checking to see if it had extended into the roof space.
Insp Bland said early investigations suggested the fire was sparked by the occupant of the home, who was welding at the time.
The fire closed Robsons Road southbound at the Reserve Street intersection. Northbound traffic on the road was turned around at the scene.
A section of Parsons Street, outside the home, was also shut.
All roads have now reopened.
Two FRNSW hazardous materials crews were also on the scene, conducting atmospheric monitoring of the heavy smoke in the area.