Abstract: Based on China's climatic regionalization standards, the study selected Changchun in the temperate zone, Chengdu in the subtropical zone, and Danzhou in the tropical zone to conduct natural aging tests on three types of fire-resistant boards (A, B, and C). The aim was to investigate the effects of different climatic regions on the physicochemical properties, mechanical properties, and fire safety of the fire-resistant boards. The findings revealed that with changing climatic conditions from temperate to tropical zones, the color difference and degree of surface degradation of the boards worsened, density significantly decreased, hygroscopicity increased, and the declines in internal bond strength and modulus of rupture exceeded safety thresholds. Boards aged under tropical climatic conditions exhibited higher peak heat release rates and toxic gas emissions, significantly increasing fire risk. For Type B boards, the peak heat release rate (pHRR) after natural aging was 573.20 kW/m², much higher than the 218.96 kW/m² observed before aging. Compared to temperate and subtropical zones, the combined effects of high temperature, high humidity, heavy rainfall, and high ultraviolet radiation in tropical regions had a more significant deteriorating impact on the performance of fire-resistant boards. Among the three types, Type A boards demonstrated the best flame-retardant performance, outstanding weather resistance, and smoke suppression stability; Type C boards showed moderate flame-retardant performance but were more sensitive to humid and hot environments; Type B boards essentially lost their flame-retardant functionality after aging, ignited rapidly in humid and hot conditions, and exhibited the poorest fire safety.

Key words: fire-resistant board, natural aging, climatic zone, physical properties, fire hazard