Three adults fainted and another had a nosebleed after the incident at a unit in the suburb of Bedford Park at about 1.30am.
It is understood hot coals were brought in to the property to try and keep the occupants warm.
The four friends were left upset by the incident.
Apsara Subedi described the situation as “very scary”, while her friend Sadikshya Aryal said she “never thought it was going to harm us even for, you know, one hour or so”.
They suffered from headaches and took painkillers as they put the coals outside and went to bed.
They were unaware they were suffering the effects of the toxic gas.
Metropolitan Fire Service Commander Wayne Trezise said the friends would have been unable to smell the gas.
“They would have just got sleepy,” he said.
Subedi woke up dazed at around 1.30am, quickly realised something was wrong and cried out for help.
Neighbour Aleena Ata said she heard her call out for assistance.
“She was just screaming out ‘help me, help me’ and there was a few people that ran out,” Ata said.
“I saw that she was being attended to.”
Subedi said she thought she was dying or had “something wrong” with her heart or brain.
“But as soon as a I saw them fainting I thought oh it could be the fire,” she said.
Authorities said the situation could have been much worse.
“It would’ve been minutes away before we would’ve had four people who would not have woken up,” Trezise said.
This is one of several similar accidents this week.
A Hectorville father and son were treated in hospital with carbon monoxide poisoning on Tuesday, while a Sydney family made the same near-deadly mistake recently.
“We can’t stress highly enough that this is very unsafe,” Trezise said.
“We need to make sure that everyone in the community does not use any form of combustion in their houses.”