More than a quarter of the electric blankets tested in Darlington were found to be unsafe.
During a two-day safety campaign, trading standards officers, along with Age Concern, carried out checks on 128 of these appliances.
It was discovered that 28% were too dangerous to use.
Over the past year, blankets which are more than 10 years old have accounted for 97% of the fires caused by electric blankets in the Darlington area.
Bill Dixon, cabinet member for neighbourhood services and community safety said: "Many people do not consider the potential dangers of using an electric blanket, especially an old or damaged one.
"I hope these checks ensure that everyone can sleep safely in their beds this winter."
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