No they are not even close to the temps that a chimney fire could get. But the outside of that brick will absolutely get hot enough to pyrolize wood over a period of time. Which will lower the ignition point to a level where the wood could ignite.
6' Liner Stuck/ Through the brick chimney?
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fire_man
Minister of Fire
I stuck a brick on top of the horizontal pipe inlet to my "T" and measured just the pipe at 301F. The top of the brick after one hour read 165F. I could see over time this temperature could cause wood pyrolosis but in a chimney combustibles are still separated from the clay or ss liner by more air spaces and masonry than just a brick. I'm not arguing that an insulated liner should not be required by code if clearances are not met or to improve draft. I'm just saying it's hard to imagine unless there was a really bad chimney fire for there to be a problem. I guess that's enough of a reason even though I keep my liners clean.
With that said, both my chimneys have insulated SS liners.
With that said, both my chimneys have insulated SS liners.
many times they are not. When a clay liner is installed there is supposed to be an air space between it and the masonry wall. But even the best mason cant keep all or the mortar from oozing out in spots or falling down that space. So best case scenario you have space most of the way but mortar tying it together in spots. There are also plenty of times the liners are mortared in on purpose. That means no air space inside then most of the time there is wood directly in contact with the outside of the chimney. It can and does get hot enough to cause pyrolisis. And after pyrolisis the lowest recorded ignition of wood was 170 degrees. So if your brick reached 165 after an hour on a 300 degree pipe you can guess that the temp could get much higher with a chimney fire burning at 2100 degrees in the liner.
Here is an interesting read on the issue https://www.doctorfire.com/low_temp_wood1.pdf
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