A man and a woman in their 50s were rushed to hospital in a critical condition after they were found unconscious inside their Perth home.
The Department of Fire and Emergency Services say the parents were using a charcoal burner in their bedroom to stay warm.
"For a long period of time they've been exposed to potential carbon monoxide poisoning," firefighters said.
The couple's teenage children discovered their parents unconscious in their home on Reddy Court.
They called triple zero and their parents were taken by ambulance to Sir Charles Gairdner Hospital.
The scene was considered so dangerous that paramedics needed ventilation before entering the house.
Concerned family members closely followed the two ambulances to the hospital where their teenage children are now by their bedside.
DFES has warned of the dangers of using charcoal as a heating device, which can cause carbon monoxide poisoning if not properly ventilated.
