1. incombustible - Noun
2. incombustible - Adjective
Not combustible; not capable of being burned, decomposed, or consumed by fire; uninflammable; as, asbestus is an incombustible substance; carbon dioxide is an incombustible gas.
Source: Webster's dictionaryIn an electric arc, PCB's generate incombustible gases. Source: Internet
Sometimes the metal was entirely incombustible, but when alloyed with osmium, it would volatilize. Source: Internet