Tumble Dryer Fires

[polygonum]

Just reading the downloaded instructions for use for a current model Bosch tumble dryer. Contains this paragraph:

Caution! Risk of fire. Laundry may catch fire. If you cancel the programme, you must remove the laundry items and spread them out so that the heat can disperse.

My question, if this is serious and not just arse-covering, surely the laundry could catch fire if there is a power cut. That being the case, and the fact many/most power cuts are not predicted (nor predictable), wouldn't we have to run back to the house to spread the laundry out whenever there is a power cut and we are using the dryer?

Have no intention of going out with it running, but given the home connect feature, it is obviously what Bosch are expecting people to do.

[Graham.]

Teutonic grade arse covering.

Incidentally, the link you posted just returns a minimalist page saying, "No correct login"

[Tim Watts]

I would have said that in practise, it is very unlikely. At uni, we had some almighty big gas tumble dryers in the laundrette. They had no cool down cycle and the clothes came out red hot - if you pulled a synthetic pair of trousers out, you literally lit the room up in static sparks.

And they used to just stop and sit in a pile when the token time ran out.

[harry]

I used to run maintenance on a commercial laundry. This perfectly true and is a common cause of laundry fires. (The other being dust.) The laundry catches fire for the same cause as damp hay starts barn fires.. Cotton and woolens being the worst culprits. The bigger the load, the more likely it is to happen.

[Brian Gaff]

So are they saying that it is merely the already warmed washing that is the risk? How can that possibly be the case. Where would the energy come from if its off either through a power cut or its turned off. Brian

[Tim Lamb]

I don't think so, Harry. Heated green hay gives off Phosphine gas from the breakdown of plant cells containing phosphorous. The gas is highly flammable.

[harry]

[harry]

In a pile of hot laundry the heat can't escape. Bacterial action/oils and greases oxidising adds to the heat.

[PeterC]

Also, as soon as the power is cut the airflow stops and the smallish amount of residual heat in the element(s), if the cut happens while the heating is on, further heats the load. It's a bit like turning off the water/power in an electric shower - the kettle boils.

[polygonum]

That is my take as well, Brian.

[Tim Lamb]

Part of the explanation. I don't think damp hay or straw is going to burst into flames at 230deg F. Manure/compost heaps get hot but you don't see them burning.

[harry]

It comes from the stored energy in the cloth fibres. As if you were burning it.

[Huge]

Apart from the one in an adjacent field that burst into flames on Thursday.

[The Natural Philosopher]

I've forked one and found ash in the centrer. That was grass cuttings from an acre and a half.

[Chris Hogg]

My understanding of rick or bale fires is that bacterial fermentation gets the warming process going, but the bacteria are killed off above say 80C by simple sterilisation. Above that temperature, slow oxidation takes over, which also generates heat, and the oxidation accelerates as the temperature rises* until eventually charring occurs and in extreme cases the rick or bale bursts into flames. Moisture content has to be within a certain range, neither too wet nor too dry.

*rule of thumb: reaction rates double for every 10 degrees centigrade rise in temperature. See Arrhenius' equation:

[Tim Lamb]

Oh! They've gone back to school here:-)

[Tim Lamb]

Sure it was ash? The residue from fungal (I think) attack can be a light coloured powder. I sold some stored hay at auction years ago. When the buyer started carting the stack he showed me where some damp bales had heated causing a plume of ashy discolouration in the layers above.

The only *accidental* hay fire here was thought to be triggered by a spark from a tractor exhaust on *overrun* carting grain in the nearby lane. The timing was right, no one was seen running away and there was some doubt about the *fit for storage* quality of the hay. The phosphine gas explanation was put forward by the loss adjuster employed by NFU Mutual.

Curiously, cattle love to eat the partly composted edge of bales that have been stored in contact with the soil.

[Huge]

It really *is* in the middle of nowhere. I'd be really surprised if it had been arson.

[Tim Lamb]

The last cattle left here in 2006 but the annual gathering of bedding straw and manure from a dairy herd of 45 plus a dozen or so followers never managed to do more than get hot. Prior to DEFRA getting excited about disease transmission, it was the traditional disposal method for small deadstock. When dung was loaded and spread by hand, I remember finding a composted calf! All that was left was the grass contents of the rumen. Presumably preserved by some chemical magic.

The agricultural community are waiting for the *disappeared* Pole to turn up when some dung is spread in a future episode of the Archers:-)

[news]

It's auto ignition temperature is very low so it ignites in the presence of air. I was given the presence of silane or phosphine as the source of ignition of swamp gas (methane) as in will o' the wisp, a phenomenon I have never witnessed.

AJH