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Case 1

How this fire happened

The elderly occupier of the house would use a microwavable wheat bag as a replacement for a hot water bottle.

She would regularly get up in the night to re-heat the wheat bag in the microwave and return to bed with the heated wheat bag.

On investigation a smouldering fire had been confined to the bed within the front ground floor bedroom.

On examining the bedding, a large quantity of what appeared to be small beans or grains was discovered within the bedding.

They appeared charred and blackened and were contained within one area.

Research was carried out for HM Coroner and the results showed that, the wheat contained in the tested microwavable personal warmers produced an exothermic reaction and thermal runaway at temperatures above 225C.

These temperatures can be produced in reasonably short periods of time in a microwave oven which is working normally.

The time is significantly reduced if the turntable is either defective or obstructed in any way, if the turntable is in-operative it can produce high temperature "hot spots" within the bag.

There was no heating information directly on the products tested.

The lack of information on the product appears to be a major contributory factor to the overheating of the wheat.

The British Standard clearly states that the product itself should be permanently and legibly marked.

Case 2

Safety message​

Like any product, wheat bags should only be used in accordance with manufacturers instructions and must not be placed in a microwave at either too high a power setting and / or for too long a time.

  • Buy wheat bags with clear heating instructions

  • Follow the manufacturer's instructions

  • Buy wheat bags which include manufacturer's contact details if you have a problem

  • Only use as a heat pack for direct application to the body

  • Ensure your microwave turntable turns freely with the bag on it

  • Watch for over-use: a smell of burning or charring

  • Leave to cool in a safe area and on a non-combustible surface like a kitchen sink

  • Use wheat bags as bed warmers

  • Overheat

  • Reheat bag until it has completely cooled (which may be two hours)

  • Leave inthe microwave unattended when heating

  • Store the bag until it has cooled

  • Use the bag if you see evidence of problems

How this fire happened

A "wheat bag" that had been left in a microwave for longer than the manufacturers recommended time caused this fire.

Wheat bags are sold in many shapes, sizes and guises from simple pads to toys and even pet beds. They are designed to be heated in a microwave oven, so that like a hot water bottle, they will slowly release their heat over a long period of time.

Wheat bags are often used as pain relief and as well as being heated can be chilled in a freezer to provide a "Cold Pack".

If used in accordance with manufacturers instructions they are completely safe, however if they are left in the microwave for longer than recommended and/or on too high a power setting they can overheat, which in some circumstances may lead to fire.

This fire can start whilst in the microwave or some time later when the wheat bag could have been placed into a bed or elsewhere. 

The effect it had


I had put the bag into the microwave, then went into the lounge while it was heating up.

I was first alerted to a problem by my Lifeline System, an operative warned me (via. their call box) to leave the house immediately.

As I passed the kitchen door I opened it to see what was happening. I now realise that this was the wrong thing to do, as thick acrid smoke billowed out, making me choke.

I quickly shut the door and left the house and waited for the Fire Brigade to arrive. They needed to use breathing apparatus to enter the house but quickly removed the microwave and wheat bag.

The house was full of smoke but I was lucky that no real damage was done. The kitchen though required a thorough clean and the whole house had a nasty smell which took several weeks to go.

I was extremely grateful for the swift action of the Fire Brigade and thankful for my Lifeline.

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