Separate inquests were held for Chesara Anna-Rose McMurdo (18 months) and Joseph James Batchelor-Smith (9 months) in Invercargill yesterday. They died within a week of each other in September 2010.
Otago-Southland Coroner David Crerar said the deaths highlighted risks associated with overheating children.
The deaths also prompted Prof Barry Taylor, of the University of Otago, to give recommendations about checking infants' body temperature.
Chesara's mother Taryn Latchford said she had put her daughter to bed about 7.30pm wearing a nappy, a stretch and grow and pyjamas.
Her daughter was lying on a sheet, with another sheet used to "tie" her in bed - loose enough she could sit up or get out if she wanted to.
She was covered with a woollen blanket and a duvet.
The house had a heat pump, which was usually set between 18degC and 24degC.
However, if the device was turned off "it would start again at 30deg and you would have to set it [down] to the temperature you wanted it to be at", Ms Latchford said.
Ms Latchford checked on Chesara about 12.30am and she was "sound asleep".
"'She was on her back with her neck and face clear and visible. She was breathing heavily.
"The duvet had been pushed back down . . . which was normal for her."
She described her as a "sweaty child", frequently waking up with wet hair and clothes.
About 6.45am when Ms Latchford checked Chesara she could see her face was blue.
"I knew straight away something was seriously wrong."
Ms Latchford said her daughter had been happy and healthy in the days leading up to her death.
The child was pronounced dead soon after an ambulance and medical staff arrived.
In their statements, some emergency staff said Chesara's room was very warm. Constable Regan Price, of Invercargill, said the heat pump remote showed a setting of 28degC.
He estimated Chesara's room to be about 25degC.
Prof Taylor, a sudden infant death syndrome researcher, said that temperature would be the maximum a child would be able to sleep in - any warmer and a child's body temperature would increase.
"This is a very rare situation ... we don't have any accurate measurements [of the heat].
"Let's just assume that it was 30deg, which would have been too hot for her . . . there is about a 1.5deg rise in body temperature for every hour.
"Within two to three hours, [the temperature] would be hitting 39 to 40deg.
"At 43, you start having seizures."
In his verbal findings, Mr Crerar found Chesara's cause of death was unexplained sudden unexpected death in infancy.
He found Joseph died from septicaemia and consequently a fever - exacerbated by overheating in his sleeping environment, resulting from a heat pump.
Joseph's mother, Georgina Daisley (nee Smith), said Joseph had been born premature following an emergency Caesarean section.
He "slept better" on his stomach, and even if put on his back, he would often turn around.
He began developing eczema and, despite Mrs Daisley applying creams, the rash did not disappear.
Mrs Daisley left Joseph - healthy except for a runny nose - in the care of long-time friend and house-mate Honey Samson.
When she left, Joseph was in his cot in the lounge, lying on his back with nothing covering him, as she expected Ms Samson would check him.
The heat pump had been set to 20degC, Mrs Daisley said.
Ms Samson, who sobbed during most of her evidence, said the heat pump had been set on 25degC.
After feeding dinner to Joseph and his 2-year-old sister, she put Joseph back to bed.
She went to bed about 10pm.
Ms Samson got up about noon to change the elder child's nappy but "just left Joseph because he was asleep".
Just before 2pm, Ms Samson sent Mrs Daisley a text message asking when she would be home, as she had a tangi to attend.
Ms Samson then decided to take the children with her to the tangi, so got the 2-year-old changed first and went to get Joseph at about 2.30pm.
"When I went to his cot I saw he was dead. He had foam coming from his mouth and nose."
Ambulance officers arrived at the scene, one remarking on the heat inside the house.
James Stronach said Joseph had been dead for some time, with his body stiff, but "warm to touch".
"The room was bloody warm - rather hot actually.
"There was no ventilation.
"Within 10 minutes I had started to sweat . . . it was at least 25degC."
Detective Sergeant Grant Johnstone, of Invercargill, said Joseph had been left about 17 or 18 hours without being checked.
However, following a full police investigation, "police are confident there are no suspicious circumstances in relation to the death".
Pathologist Noelyn Hung, a senior lecturer at the University of Otago, examined Joseph and found his death was attributed to an acute episode of septicaemia with an associated fever, exacerbated by the heat in his home environment.
It was likely the bacteria in his bloodstream had come through his eczema sore.
Analysis of his urine indicated his muscles had begun to break down and had gone into his urine - a process which would have occurred before his death.
Prof Taylor said the most likely cause of that was "a very high body temperature".
Heating homes
- Heat pumps circulate air, so there is a more even air temperature.
- A room heated by a fire typically has cooler air at lower levels.
- Living rooms should be heated to 22degC-23degC.
- Ideal bedroom temperature is 17degC-18degC.
BABIES AND HEAT
- Infants are unable to self-regulate their temperatures.
- To assess a baby's temperature, put a hand behind their neck for core temperature.
- Hands and feet should be slightly cooler.
- If hands and feet are as hot, they are trying to get rid of heat.
Source: Prof Barry Taylor, University of Otago
