Linseed oil is the usual culprit. It oxidizes more readily than other oils at room temperature, and a pile of rags can insulate enough for the center to reach autoignition temperatures. The low smoke point for linseed oil also makes it well-suited for seasoning cast-iron cookware (only be sure, please, not to use boiled linseed oil, as it contains lead.)
Linseed oil is just flaxseed oil, and I've found that the latter term is used in cooking contexts, whereas linseed oil is a term used in various industries that use industrial grade flaxseed oil.
I make this distinction because when I went to buy "linseed oil" to cook with on Amazon a while back, it brought me to various linseed oils that were not meant for human consumption.
My wife uses linseed oil on cast iron. Almost as good as non-stick. Linseed oil has a lot of triply unsaturated α-linolenic acid, which is reactive (due to multiple double bonds) and supports polymerization. A few thin layers of linseed oil added to cast iron and baked to the smoke point create a beautiful sheen and make it easy to clean.
You want it to smoke when seasoning. That's an indication that free-radicals are being created which set off the polymerization of the oil and create the seasoning. Low smoke-point oils are more convenient because they start polymerizing at lower temps.
This is a glaring connection I rarely see people make.
In fact, I've been banging on about it for 15 or so years, and, I kid you not, you're the first person I've seen being this up.
Strange!
Unusual cross section of knowledge: I studied nutritional medicine in a formal capacity for four years 2000 through 2003 inclusive, and I'm also a welder by trade.
At the cross roads of knowledge domains interesting conclusions can be drawn, and sometimes fruitful cross pollination occurs. One thing about the successful founders that I know is that they are not confined to just one domain, and I have been wondering for a long time if that is a trait that helps them to be successful.
Lead oxide is a catalyst to polymerization. For wiping down and protecting wooden tool handles it's nice to have the oil harden quicker at room temperatures.
