how do lipos go up in smoke/ flames?

I stuck a stick in one and punctured the wrapper/skin. No real fire, never saw flames, but tons of smoke and it got hot enough that it would have melted chassis if I hadn't managed to get it out. I protect mine in the car better now and I don't drive in piles of woody trash that can have sharp sticks in them anymore!

I charge mine on a thick porcelain dinner plate.