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Fire caused by an overheated wheatbag

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Contents of the wheat bag which caught fire on the bed

Contents of the wheat bag which caught fire on the bed

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The bed damaged in the fire.

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Demonstration of the temperatures to which a wheat bag can be raised

Demonstration of the temperatures to which a wheat bag can be raised.

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 225oC.

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.

The effect it had

Safety message

Safety Message - Do
  • 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
Safety Message Don't
  • 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

Further information

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.

Do you have a similar story?

Finally, we would be interested to hear from you if you have had a similar experience to the fire detailed above, or would like to raise any related matters or even just generally comment on how useful you found our Black Museum.

Please send us your details and a comments via our on-line feedback form.


This case study was contributed by:

West Yorkshire Fire and Rescue Service website


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Black Museum Survey
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Latest Update :
01 October 2020
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