Smart fire alarm systems for rapid early fire warning: Advances and challenges

The serious fire accidents happen frequently every year worldwide, which kill many lives and result in a sig-nificant property loss. The sensitive fire alarm systems (FASs) that can timely detect the early fire and imme-diately give the alarm are therefore urgently needed. The traditional FASs based on smoke and infrared heat detectors suffer from sluggish fire warning and susceptibility to external interference. How to make a sensitive and reliable FAS remains a big challenge. As such, a new-style FAS based on graphene oxide came into being in 2018. The fire response time could be as short as <1 s, indicating its intrinsic high sensitivity. Since then, diverse smart FASs have been extensively developed, including MXene-based, semiconductor-based, color change-based, shape change-based, thermoelectric material-based and nanogenerator-based FASs. During five-year develop-ment, this research field has witnessed a rapidly evolving trend. Up to date, there is still lacking in a compre-hensive review of this research field. This article aims to provide a thorough review of recent advances in smart FASs, summarize the working mechanisms and mainstream preparation methods, and propose the challenges and future research directions. It is believed that this review article will provide an instructive guideline for designing smart FASs and stimulate extensive interest for materials scientists.