You can get the extruded foam with or without a flame-retardant additive.
Yes, this was printed on the sheet in the photo:
"FOAMULAR insulation is combustible, but contains a flame retardant additive to inhibit accidental ignition from small fire sources. During shipping, storage, installation and use, this material should not be exposed to flame or other ignition sources."
I do not think the Foamular (Owens-Corning brand) is made without the flame retardant, at least I have never seen it.
