incombustible
in-com-bus-ti-ble
adjective
Unable to burn or catch fire; resistant to combustion.
"The new insulation is completely incombustible."
Thesaurus
Synonyms: fire-resistive, nonflammable, noncombustible, flame-retardant, fire-resisting, fire-resistant, fire-retardant, fireproof, flameproof
Antonyms: combustible