A 1-year-old baby died during his sleep in the central province of Quang Nam after his family burned charcoal to heat their room the whole night.
His parents are receiving medical treatment.
The boy’s grandmother broke into the room after none of them showed up on Wednesday morning, only to find it was filled in smoke.
His parents, 19 and 20 years old, burned charcoal in an oven and put it under their bed the previous night to keep their baby warm.
They also shut the door and window to keep the wind out.
Nguyen Thi Hoa, the grandmother, said she had knocked the door and no one answered.
“When I came in, they were all lying in bed unconscious.”
They were rushed to hospital but the baby died on the way.
The father is still in a coma while his wife was able to sit up.
Families in rural areas in central Vietnam have the habit of burning coal for heating. There is also a Vietnamese tradition to burn coal to warm newborns and women during their first postnatal weeks.
Experts have highly recommended against the practice as saying that it can emit poisonous gases such as SO2, NO2 and CO that can cause respiratory inflammation, cancer or deadly suffocation in a closed room.
This is not the first time the practice has resulted in tragic deaths.