<p>The present study employed phytic acid as the primary phosphorus-based flame-retardant material to establish a composite intumescent flame-retardant system that integrates melamine, which provides a nitrogen-based flame-retardant mechanism, and chitosan, which exhibits <b>good</b> char-promoting and carbonization properties. Under high-temperature conditions, this flame-retardant system is capable of forming a dense and stable char layer as evidenced by the observed char morphology and barrier properties, the flame retardant provides partial insulation against heat and oxygen. This flame retardant was incorporated into epoxy to reduce the inherent flammability of the material. To explore the flame-retardant behavior and mechanisms of this system, this study employed the cone calorimeter test to evaluate key parameters such as the heat release rate, total heat release, smoke production rate, and total smoke release. The results revealed that under simulated fire conditions, the incorporation of the chitosan-based flame retardant reduced the peak heat release rate from 800 to 574&#xa0;kW/m², the total heat release from 24.3 to 21.7&#xa0;MJ/m², the peak smoke production rate from 0.303 to 0.200 m²/s, and the total smoke release from 953.1 to 532.8 m²/m². These findings demonstrate the effectiveness of the proposed flame-retardant system in reducing heat and smoke emissions during combustion.</p> Graphical Abstract <p></p>