Australian authorities have expressed their concerns over the safety of domestic heaters following the death of two children in their home in Victoria.
The bodies of Tyler Robinson, 7, and his brother Chase, 9, were found inside their house at Mooroopna on Sunday.
Energy Safe Victoria examined the house and police believe a gas leak was responsible for the boys' deaths. Inspections have revealed a faulty gas appliance, possibly a heater.
The boys' 29-year-old mother, Vanessa Robinson, was taken into police custody for questioning, but was later admitted to hospital after becoming disoriented and falling ill.
The boys were students at the Mooroopna Primary School and the principal, Steve Rogers, has said students and teachers have been offered counselling.
Young children are most at risk from faulty heaters, Energy Safe Victoria has warned.
As people seal up their homes to keep the warmth in and the winter cool out, they could be killing themselves by not allowing adequate ventilation, industry experts have warned.
Carbon monoxide and nitrogen oxide are the most common forms of poisoning from heaters. Symptoms initially include a headache and feeling like you have the flu, they can occur immediately or take some time.
If exposure lasts long enough an affected person could fall asleep and never wake up, said Rick Taylor, gas division chairman of the Master Plumbers and Mechanical Services Association of Australia.
The vital issue with gas heaters is ventilation," Mr Taylor told AAP on Wednesday.
Mr Taylor said gas heaters were dangerous because they consume all the oxygen in the room leaving none for a person to breathe.
He suggests opening a door or a window to allow for ventilation.
Heaters should be serviced at least once every two years, Mr Taylor said.
On its website, Energy Safe Victoria warns unflued gas heaters should never be used in a room where you sleep.
"Young children and people with asthma or other respiratory diseases are most at risk from air pollutants," the website says.