Over-heating contributed to the death of a 10-month-old boy who slept in a room near a heater set at 25C and wasn't checked on for 18 hours, a coroner has found.

About 8.30pm on September 25, 2010 Joseph Batchelor-Smith's babysitter Honey Samson dressed him in one layer of clothing, wrapped him in at least two blankets and put him to bed in a cot near the heat pump.

Joseph's mother Georgina Daisley had left her son in the care of Ms Samson - who also stayed at the Gore home - for the night.

About 18 hours later, just after 2.30pm the following day, Ms Samson checked on Joseph and found him unresponsive.

Ambulance staff who were called to the scene described Joseph as being "stiff," a bluish colour and frothing at the mouth and nose. He had likely been dead for some time.

An ambulance officer also described the room as "rather hot" and had no ventilation.

In his finding David Crerar concluded that Joseph had died from an acute episode of septicaemia and consequent fever that was compounded by a heated environment.

An autopsy found that Joseph was a "well nourished" baby and there was no evidence of injuries.

However, he was considered a "vulnerable" baby as he was born premature, had a low birth weight and because his mother smoked heavily during her pregnancy.

In the two weeks prior to this death Joseph suffered from the skin rash eczema which causes the skin to break and can increase the risk of infection.

Mr Crerar said while there was no evidence to show that Joseph's life could have been saved if he had been checked on earlier, it was "of concern" that he had not been checked for 18 hours.

He ordered a copy of the report be sent to the Child and Youth Mortality Review Committee for review.

He also issued this warning: "Babies do not have a well-developed dissipation mechanism and care needs to be exercised by parents and caregivers that babies no not overheat."