Re: Plastic pipe article
When CPVC is exposed to a flame, it will simply char. This char layer then becomes a thermal barrier, which restricts the flow of heat into the pipe and reduces the rate of burning. PEX, on the other hand, is highly flammable and will continue to burn even after an external flame has been removed.
Tests additionally show that CPVC pipe does not contribute to flashover, which is the sudden, explosive development of a flame front.
Some reason in the book it shows a picture of the pipe exterior charred, like that intermessent stuff.