40d:Fire-safe

Fire-safe materials are building materials that cannot catch on fire. These include stone, glass, and metal. Wood is not a fire-safe material, and neither is charcoal or coke (even though they are bar). Fire-safe materials are only required when the object is going to come into contact with extreme heat, such as a wood furnace, smelter, forge, kiln or glass furnace, or for magma versions of these facilities.

Flux materials, such as limestone blocks, which are consumed in the purification of pig iron to produce steel, are considered fire-safe. It is perfectly fine to use limestone as a flux material to make steel in a limestone smelter. Ice is also a fire-safe material... somehow. Constructions will never melt or burn, but natural ice walls/floors/ramps/stairs will.

Note that constructions (Wall, Floor, Ramp, Stairs) can never burn, regardless of what they're made of.

Not to be confused with magma-safe materials. Many fire-safe materials will still melt when in submerged in magma, but that is not necessary for buildings that are powered by the stuff or items like doors or grates that may be adjacent to or in contact with magma, but are never surrounded on all sides by it.