It is worth noting that PVC is not combustible. It melts at a low temperature, it burns when a flame is held to it (so will steel and aluminum), and when it burns it gives off extremely toxic fumes, but it will not sustain a flame on its own. At least 1 website claims that the IRC requires a minimum of 28 gauge steel for dryer ducts. They did not quote the paragraph giving this requirement. I presume that any such requirement (if it exists) is there with the intent of containing small lint fires inside of the duct. 30 gauge steel seems to be the standard product to use, though. Does anyone know if this 28 gauge minimum is real? My question is how much clearance is needed between an ABS DWV pipe and a dryer duct? I am concerned about overheating the ABS pipe and causing it to deform or melt. Without making the duct difficult to route, I end up with about 1 inch of clearance to the bottom of the washing machine standpipe P trap.
