There some stable up to 217c and also it seems that they dont ingnite easily or offgass anything toxic.
From the Ultem website (thanks Abysmal!)—see Toxicity paragraph):
GENERAL INFORMATION
DESCRIPTION
The ULTEM Resin family of amorphous thermoplastic polyetherimide (PEI) resins offers outstanding elevated thermal resistance, high strength and stiffness, and broad chemical resistance. ULTEM is available in transparent and opaque custom colors, as well as glass filled grades. Plus, ULTEM copolymers are available for even higher heat, chemical and elasticity needs. ULTEM resins uniquely balance both mechanical properties and processability, offering design engineers exceptional flexibility and freedom.
BENEFITS
LONG-TERM HEAT RESISTANCE
Excellent stability of physical and mechanical properties at elevated temperatures thanks to high glass transition temperature of 217 °C. Available with relative thermal indices (RTI) up to 180 °C
STRENGTH AND STIFFNESS
Outstanding strength and amorphous thermoplastic among the available alternatives, with predictable stiffness and strength up to 200 °C. Unfilled, transparent grades are equal in strength to other thermoplastics with opacifying fillers.
DIMENSIONAL STABILITY
Among the most dimensionally stable thermoplastics available, offering predictability over a wide temperature range. Filled grades offer exceptionally high-tolerance dimensional capabilities.
ENVIRONMENTAL STRESS & CRACKING RESISTANCE
Unlike most other amorphous thermoplastics, ULTEM resins retain strength and resist stress cracking when exposed to automotive and aircraft fluids, aliphatic hydrocarbons, alcohols, acids, and weak aqueous solutions.
FLAMMABILITY, SMOKE GENERATION AND TOXICITY
Inherent flame resistance without additives in most grades - exceptionally difficult to ignite, with a limiting oxygen index (LOI) of 47%, meeting UL94 V0 specifications in sections as thin as 0.41 mm. Generates extremely low smoke per the NBS smoke evolution test, with products of combustion no more toxic than those of wood.
PROCESSABILITY
Can be extruded, thermoformed, extrusion blow molded and injection molded, and flowability permits long flow lengths down to 0.2mm thick using conventional injection molding equipment.
GRADES
GRADES AVAILABLE: 122 (Clear Filters)