There could be a new element that would be called TTLI (Total Insulator), NFLI (Non-Flammable Insulator) or whatever.
This element would have the same propreties as Insulator ; the only difference would be that it is not flammable.
Color: dark gray
Category : Special

Uses: Storing LAVA, FIRE..., Chimney for power plants, rockets engine, PLUT (or anything flammable) power plant insulation...