Here is a small improvised and non.scientific "test" of fire resistance (or flammability however you want to look at it) of various Shapeways 3d printing materials. The results are not surprising, basically gypsum burns worst. Don't try this at home folks. Plastics is flammable.
Tested materials were: Alumide (metallic plastic) UV Cured Acrylic Resin (Frosted Ultra Detail & Detail Plastic), Gypsum Full Color (full color sandstone) and Nylon (white, strong & flexible).