Mrs Ghiloni used the wheat bag as a hot water bottle
A warning has been made about the "devastating" effects of overheating microwaveable heat bags following the death of an elderly woman in Leeds.
Doreen Ghiloni, 82, accidentally set fire to her bedding with an overheated wheat bag last May.
She was taken to hospital but later died from respiratory failure brought on by the inhalation of toxic gases.
A coroner and West Yorkshire fire service have urged people to be aware of the dangers of such products.
An inquest in Leeds was told the bag was heated for too long in the microwave and then set fire to Mrs Ghiloni's bedding at her home in Redhall Way.
She was rescued from her home by a neighbour on 22 May but died later in Leeds General Infirmary.
West Yorkshire coroner David Hinchliff recorded a verdict of misadventure and said he would write to British Standards safety chiefs to highlight concerns over the use of the bags.
Speaking after the inquest Chris Clarke, from West Yorkshire Fire and Rescue Service, told BBC News there had been two other fatalities in the country as a result of overheating such bags.
He said: "We want to get the message out that these wheat bags can be dangerous if not used correctly and the way the manufacturers recommend for them to be used.
"Once they've been overheated they start a rapid smouldering process and can reach extremely high temperatures of over 700C.
"If that comes into contact with combustible material we can have a devastating fire."
Mr Clarke added: "The most important thing is to read instructions. It's about education and we want to get the message out these need to be used in accordance with manufacturers' instructions."