I was watching a show on TV (Smash Lab) where they installed thermocouples inside a small house that was being used to test a fire-resistant insulating blanket for the exterior of the house. It made me wonder about how long the thermocouples would provide readings if the house caught on fire. If someone did want to install a network of sensors in a building that was going to be set on fire, what’s the best way of doing it? The insulation on common wire melts at a relatively low temperature. Is there wire available that is designed to survive extremely hostile environments, like a structure fire? What about other electrical/electronic components? Assuming that money is not a problem, what’s the maximum temperature that is considered a survivable operating environment?
Wire is available with woven fiberglass insulation (there’s probably some old asbestos insulted wire still out there, too), but if you really wanted to measure the temperature inside a house fire, and money was no object, I would design a wireless Infrared temperature measurement device, and then put it inside a high-temperature insulator (like a hollowed-out furnace block), with only a tiny hole for the sensor to look out.
I’m pretty certain the insulation used on high temperature thermocouple wires is made of glass fibers. For very higher temperature use, I’ve used short segments of ceramic cylinders on each wire.
Kapton insulation is rated to 400 degrees C.
High temperature wire used in ovens is insulated with a silicon rubber core and a woven fiberglass sheath. IIRC, it is rated to 600 °F.
You can get much higher temperatures than that. Thermocouples of the Magnesia Insulated Metal Sheathed construction can go well into red heat. Only a little more exotic are halfnia insulated ones. Tantalum thermocouples with halfnia insulation can go to 2300 C for long term use.
To learn the easiest way of doing it, you might want to check with the folks at NIST. Over the years, they have done full size modeling of residential and other occupancy fires, studying flashover, smoke propagation, and issues important to the fire service.
At a previous job I used bare metal Type C (tungsten alloy) thermocouples w/ ceramic insulation. One caveat is that they can only be used in a vacuum. We also used type S in air. But damn those were expensive…
Early 1900’s knob and tube electrical wiring would probably survive a fire. The ceramics would last quite a while – probably longer than the wood frame they are installed in.