Residents are being urged to take care when heating wheat bags after firefighters were called out to a flat in Birkenhead.
Merseyside Fire & Rescue Service was called out to Park Road East just before 6.30pm on Monday after a wheat bag overheated and caught fire in a microwave.
The blaze is the third this year involving such a device.
Firefighters believe the wheat bag may have accidentally been left in a microwave for too long and overheated.
Two men, aged 70 and 38, suffered suspected smoke inhalation. They were assessed by paramedics but refused hospital treatment.
Earlier this month firefighters visited more than 50 homes in a community to warm of the dangers of wheat bag warmer following a blaze in Birkett Road, Birkenhead.
This month's fires come after the death of 83-year-old Norma Hickey.
Earlier this year, an investigation into the cause of the fire at the property in Village Way, Wallasey – where the body of Mrs Hickey was discovered – found the most likely cause of the fire was thought to have been a microwavable wheat bag that had been overheated and then used to warm a bed.
Merseyside Fire & Rescue Service has since released fire safety advice in relation to the use of wheat bags.
Group Manager Paul Murphy, Wirral District Manager, said: "A product like this, which absorbs and stores heat in this way, is a potential fire risk if it is not used correctly. It is for this reason that it is vital to follow manufacturers’ instructions to avoid possible injury.
"These products can be dangerous if they are not used correctly and we are urging people to follow advice on their use to reduce the risk of a fire occurring.
"We would urge people to always follow the manufacturers’ guidelines."
Wheat bags are generally used to treat aching muscles. Those bought in shops have manufacturers' instructions which recommend maximum heating times. Homemade bags can pose a greater risk because the type of wheat may be unknown and there are no manufacturers' instructions to follow.
If a bag is kept insulated after heating - for example, under bedclothes - it may ignite.
Merseyside Fire & Rescue Service is also issuing the following advice:
• Buy wheat bags with clear heating instructions from the manufacturer, and follow them.
• Buy bags which include
manufacturers’ contact details if you have a problem.
• Only use as a heat pack for direct application to the body.
• Ensure your microwave turntable is working properly.
• Watch for signs of overuse, such as a smell of burning or charring.
• Leave bags to cool in a safe area and on a noncombustible surface like a kitchen sink.
• Use a wheat bag as a bed-warmer.
• Overheat the bag.
• Reheat the bag until it has completely cooled – which may take up to two hours.
• Leave the microwave oven unattended when heating.
• Put the bag away for storage until it has cooled.
• Use the bag if you see evidence of problems.