Abstract: Seized return idlers are one of the main causes of fire in belt conveyors. To investigate the frictional heating characteristics of seized return idlers in belt conveyors, a combination of platform experiments and numerical simulations was used to study the effects of conveyor belt speed, roadway airflow velocity, and ambient temperature on the temperature of the seized return idlers. The results indicated that the temperature of the seized return idler increased significantly with the rise in ambient temperature and conveyor belt speed, and the time required to reach thermal equilibrium was prolonged. An increase in roadway airflow velocity effectively reduced the temperature of the seized return idlers and shortened the time to reach thermal equilibrium. To further assess the fire risk from coal dust accumulation within stuck rollers due to belt wear, the study explored the effects of conveyor belt speed, roadway airflow velocity, ambient temperature, and coal dust accumulation ratio in the seized return idlers (defined as the ratio of accumulated coal dust volume to the maximum capacity of coal dust volume in the idlers) on the maximum temperature of the coal dust. The results revealed that the effects of conveyor belt speed, roadway airflow velocity, and ambient temperature on the maximum temperature of coal dust in the seized return idlers were consistent with their effects on seized roller temperature. Additionally, an increase in the coal dust accumulation ratios in the seized return idlers resulted in a more significant rise in coal dust temperature. Under conditions of an ambient temperature of 20 °C, conveyor belt speed of 3.5 m/s, roadway airflow velocity of 1 m/s, and a 100% coal dust accumulation ratio, the maximum temperature of coal dust reached 87.5°C, which was 43.2 °C higher than that at a 25% accumulation ratio. This temperature exceeded the threshold value of spontaneous combustion for low- to medium-grade coal, indicating a substantial increase in fire risk.