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Carbon monoxide death, electric storage heater

This incident happened in the UK about eight years ago. I mentioned it on the Wall about 5 years back and someone later made a post asking about the details. I had assumed, incorrectly, that the carbon monoxide must have been produced from dirt or lint on the heater element. 

  I recently searched the internet  for more details and found that someone had obtained the details from the UK Health and Safety Executive under Freedom of Information legislation. The original thread is here;

<a href="http://www.theiet.org/Forums/Forum/messageview.cfm?catid=205&threadid=7152&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear">http://www.theiet.org/Forums/Forum/messageview.cfm?catid=205&threadid=7152&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear</a>


The details of the incident are copied and pasted below. I am posting this simply because the incident was so unpredictable and it is of interest to anyone in the heating business.

 An electrician had repaired the heater by shorting out the thermal fuses with fusewire and apparently failed to notice that both the control thermostat and the overheat thermostat had failed On, by the contacts welding themselves together. He was prosecuted, but the case was abandoned because it was thought that a competent technician could not have anticipated that the heater could emit carbon monoxide.

 "I finally got to the bottom of it, thanks to documentation sent to me from the Health and Safety Executive under the freedom of information act. Copyright and discretion prevents me from providing verbatim extracts from the very comprehensive information I received, but here is my precis.

This was a 10kW storage heater (made up of nine heating elements - selectable for heat demand), with both off-peak and continuous mains supplies connected.

Cast iron core temperature was controlled at 660 degs C by thermostat, in series with;

a safety thermal trip (manual reset), set to 740 degs C.

A final safety feature was three thermal fuses, each controlling a section of the heater bank. These fuses were located in the outer casing of the heater and would have opened at 202 degs C.

Failure mode was;

Thermostat AND thermal trip had both failed closed (ON). That is assumed to have caused an overheat situation which had opened all three thermal fuses and rendered the heating inoperable.

The repair in question had been completed by shorting out the three thermal fuses with fusewire.

Following that repair, the heater was put back into service.

Unknown at the time was the fact that the off-peak timeswitch had an intermittent fault whereby instead of providing power for just seven hours overnight, it occasionally stayed powered for over 79 hours.

All the above elements combined to keep full power on the heater bank in all probability for over 79 hours .

That caused the cast iron heater core to reach a temperature in excess of 1100 degress C. So hot that the core had melted in places. HSE scientists advise that at these elevated temperatures, the carbon composition in cast iron can part oxidise to create carbon monoxide. They estimated that up to 600g of carbon had been lost from the core in that way. (About ten times the amount needed to create a lethal concentration of CO in the flat.)

As CandG2330Student suggested much earlier in this thread, "If [he] wasn’t going to kill the tenant by this rare CO incident, [he] was probably going to burn the place down while he was asleep in bed."

I'm pleased I got to the bottom of this. In the end though, and I will quote this line from the official report, "This tragic event should serve to remind everyone of the possible consequences of shorting out or by-passing safety devices"."


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853

    I think I would have smelled the melting metal and realized that SOMETHING wasn't right. And the GLOW of the radiant energy coming from the slag heap should have caught someone's attention.

    Just when you think you've seen it all....

    Thanks for the contribution,


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  • Tim McElwain
    Tim McElwain Member Posts: 4,628
    Brings to mind

    a call I had many years ago, Lady called the gas company said she smelled gas in her kitchen. When I arrived she advised she did not smell it anymore. Further questioning determined she had smelled the smell when the oven (electric) was on the self cleaning mode. Her husband had pulled the 240 wire disconnecting the electric range.

    When it was reconnected and placed in self cleaning mode I was able to get over 200 PPM of CO and climbing. I learned something new that day, it is not just fossil fuels that can cause CO. Jim Davis many years later agreed with me concerning that little fact. If you don't test you don't know.
  • rlaggren
    rlaggren Member Posts: 160
    Self cleaning ovens causing CO

    Glad to get that info. Never would have thought it and there's a lot of those ovens out there. CO detectors looking more important all the time.

    disclaimer - I'm a plumber, not a heating pro.
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,548

    Thanks so much for sharing this.
    Retired and loving it.
  • landmobile
    landmobile Member Posts: 9
    Fascinating story,

    I used to think that electric heating was immune to CO as well, but in my work as a firefighter we have seen several non-combustion CO incidents. 

    The most recent advisories have described very high levels produced by the overheated plastic handles of pots that were stored in an oven that was accidentally turned on. We have also responded to malfunctioning appliances with battery backup (such as sump pumps) that have produced high levels of CO.

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