Influence of wind velocity on miners’ safe working limit time in high-humidity and high-temperature environment

In order to study the influence of wind velocity on the safe working limit time of miners in a humid and hot mine, five experienced mine workers were selected as subjects to exercise labor simulations with moderate intensity under 24 different mine environments simulated by an artificial microclimate room. While recording the experimental time, their physiological indicators were measured: heart rate and rectal temperature, therefore to determine safe working limit time of the miners. There are 4 groups of wind velocity are set: static wind（wind velocity less than 0.2 m/s）, low velocity wind（1 m/s）, medium velocity wind（2.5 m/s）, high velocity wind（4 m/s）, 3 groups of temperature are set: 26, 30, 34 ℃, 2 groups of relative humidity are set: 70%, 90%. According to the experimental data, the Cox regression method and survival function method are used to analyze the effect of wind velocity on the safe working limit time and the recommended value of safe working limit time is given. The result shows that: the influence of wind velocity on miners’ safe working limit time is greater than relative humidity but less than temperature. Among the four wind velocity types, the order of survival rate decline rate from high to low is: static wind>low velocity wind>medium velocity wind>high velocity wind. Increasing wind velocity can effectively increase the value of the safe working limit time, but the effect is not great when the wind velocity reaches 2.5 m/s.