Consumer Product Safety

NITE Alert_84

November 22, 2007

Safety alert on preventing accidents linked to
"Charcoal briquettes kotatsu" (mametan kotatsu)*

*foot warming table with a coverlet to be heated using charcoal

In the ten years between 1997 and 2006, there have been 11 cases of fire accidents likely to have been caused by charcoal heated kotatsu, or mametan kotatsu, resulting in multiple serious accidents, including fatalities and burnt-down properties. With the kotatsu season just around the corner, this alert has been issued to provide accident examples and to encourage consumers to pay attention to the proper use of kotatsu.

Structure of charcoal heated kotatsu

The kotatsu uses charcoal briquettes as a heat source. Lit charcoals are put in a fire grate with insulating material inside the lid, and placed inside a receptacle underneath the table.


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Examples of accidents

Case 1
[presumed cause]
A fire broke out from a two-story wooden house and burnt out approximately 165 square meters.A charcoal heated kotatsu was found burning by one of the residents.It was presumed that the non flammable cotton (insulation material) used in the fire grate may have deteriorated and diminished and lost is insulating properties. The coverlet attached to the table may then have been overheated by the charcoal briquettes in the fire grate and ignited.
Case 2
[presumed cause]
A residential house was destroyed by a fire and a body was found at the fire scene.It was presumed that the tabletop of a charcoal heated kotatsu caught fire from the charcoal briquettes as the insulation material in the fire grate had a hole.
Case 3
[presumed cause]
A fire started from a two-story wooden house, which burnt out approximately 200 square meters. It was presumed that a charcoal heated kotatsu was used with its fire grate not fully closed because there were too many charcoal briquettes in it, and the flammable materials nearby may then have caught fire from the charcoals.
Case 4
[presumed cause]
A fire started from a two-story wooden house and destroyed approximately about 53 square meters.It was presumed that the coverlet attached to the kotatsu caught fire from charcoals briquettes in a broken container.

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Items need special attentions of users

  • 1.Always be sure to check nonflammable material* in the fire grate before using kotatsu.Check to see whether it was not damaged or perforated. Do not use in case it was deteriorated or perforated.
    • * materials, such as rock wool and glass fiber cotton flock are used for insulation.
  • 2.Insulation material should be changed regularly as it is expendable.Be sure to inspect or replace it around the time of replacement (about two years) indicated on the operational manual.Failing to do so may not only cause fire, but may also lead to abnormal combustion of charcoals which may result in carbon monoxide poisoning.
  • 3.Make sure to put the temperature control lever to "completely close" as well as to make an opening by rolling up the coverlet's hem before going to sleep or leaving room for prolonged time.
  • 4.Read the manual carefully to for proper operation and safety.
  • 5.In case of finding any irregularity, immediately stop using the product and contact the manufacturer.

Fore more information;
National Institute of Technology and Evaluation (NITE)
Product Safety Technology Center, Product Safety Investigation Division

Contact us

 Risk Analysis and Public Relations Division  Product Safety Technology Center  National Institute of Technology and Evaluation
Phone number:+81-6-6612-2066
Fax number:+81-6-6612-1617
Address:1-22-16, Nankokita, Suminoe-ku, Osaka-shi, Osaka 559-0034 Japan MAP