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Fire prevention and safety of combustible materials is a global challenge. To reduce their high fire risk, traditional smoke detectors are widely used indoor via detecting smoke product after combustion; however, they usually show a long response time and limitation for outdoor use. Herein, we report a temperature-induced electrical resistance transition of graphene oxide wide-ribbon (GOWR) wrapped sponges to reliably monitor fire safety of the combustible materials. Novel rectangle-like GOWR sheets are synthesized from unzipping carbon nanofibers and used to fabricate GOWR wrapped melamine formaldehyde sponges with multi-functionalities, e.g. lightweight, good hydrophobicity, reversible compressibility, excellent acidic/alkaline tolerance and flame resistance. The GOWR sheets on the sponge skeleton can be in-situ thermally reduced once encountering a flame attack or abnormal high temperature, inducing a distinct transition in electrical resistance. Consequently, an ultrafast alarm response of ∼2 s to flame attack is triggered, and rapid fire early warning signals to abnormal high temperatures, e.g. ∼33 s at 300 °C, are achieved below ignition temperature of most combustible materials. This method drives substantial motivation and opportunity to develop advanced fire detection and early warning sensors for reducing the high fire risk of various combustible materials in outdoor applications.