Interrupting dryer mid-drying cycle is a fire hazard?

[Machine_Elf]

@Dead_Cat

Of course not. But if they don’t, and then suffer some mishap that the manufacturer warned about in the manual, they’re unlikely to have much luck getting compensation.

Putting a warning in the manual may scare off a potential lawsuit here or there. But if you get hurt doing a thing that pretty much everybody does as a matter of course - or that the machine may do by itself during a blackout - a warning doesn’t absolve the manufacturer of responsibility for making an inherently dangerous machine.

[Melbourne]

In any case leaving hot damp clothes in the dryer, is a way to get creases in your clothes, and probably not what you want to do anyway.

And I’ve had a young man “turn off the dryer” because the contents were too hot (instead of advancing it to the cooling cycle), which, while it didn’t start a fire, indicated a disappointing level of ignorance of both physical reality and the way clothes dryers work.

[YamatoTwinkie]

@Machine_Elf

The question is whether there’s enough residual heat available to raise that ductwork/lint to dangerous temperatures. Smart manufacturers will design their dryers so that this is impossible (through some combination of duct design and thermal fusing), because it’s guaranteed that a user somewhere will interrupt the cycle at some point (regardless of what the owner’s manual might tell them), and then will sue the manufacturer if a fire happens.

Sure, but there is always the possibility that there are other component failures or lapses in required maintenance that, when combined with the cycle interrupt, may be just enough to push it over the edge.

I think typical thermal fuse/cutoff temperature on the heater box is 350F. It normally doesn’t ever get there unless there are problems with airflow (lint obstruction in the dryer exhaust), or problems with the high limit thermostat.

I’d hope that the system was designed so that a cycle interrupt while the heater box is already sitting right at the 350F fuse limit isn’t going to have enough retained heat from the element to spike temperatures further near the ignition point of lint (~500F?).

I think if you’re really concerned about dryer fires enough to avoid interrupting the cycle, you’re 1000x better off just channeling that energy into cleaning out the dryer ductwork regularly, vacuuming out the interior, and ensuring you’re using rigid exhaust hookups. But there’s still some benefit to the practice.

[Melbourne]

@YamatoTwinkie

I’d hope that the system was designed so that a cycle interrupt while the heater box is already sitting right at the 350F fuse limit

If the materials are stacked or binned at high enough temperatures (above [194 degrees F] ), the heat accumulated in the centre of the pile may be enough to trigger spontaneous ignition of the cotton materials.
Self Heating and Spontaneous Combustion - SAMFS

So, the ‘danger’ is that you let the dryer run hot, then stop it before the cooling cycle, and leave the clothes in it. High-temperature decay of the cloth releases heat faster than the packed cloth can disperse it, and eventually the centre reaches smolder temperature, then ignition temperature.

With wet cotton there is a mold problem: I know it can make the cotton hot, but I don’t know if it’s associated with fire risk in dryers? Oily cotton is like dry cotton, except it catches fire and burns at a much lower temperature, instead of smoldering for hours and maybe going out. Oily cotton was a much bigger problem when more people used cotton rags and oil-based paints.

Anyway, none of this is ‘interrupting’ the drying cycle. It’s stopping the cooling cycle with hot fabric left tightly packed in the overloaded machine.

I agree that if this was a real problem with power interruptions, electric dryers would not be approved for home use. 90C is much hotter than the end of a normal drying cycle, so if your dryer is getting that hot, interruptions to the power supply are not your only problem.