A Method to Protect Mine Workers in Hot and Humid Environments

Abstract

Background: Work comfort studies have been extensively conducted, especially in the underground and meteorological fields resulting in an avalanche of recommendations for their evaluation. Nevertheless, no known or universally accepted model for comprehensively assessing the thermal work condition of the underground mine environment is currently available. Current literature presents several methods and techniques, but none of these can expansively assess the underground mine environment since most methods consider only one or a few defined factors and neglect others. Some are specifically formulated for the built and meteorological climates, thus making them unsuitable to accurately assess the climatic conditions in underground development and production workings.

Methods: This paper presents a series of sensitivity analyses to assess the impact of environmental parameters and metabolic rate on the thermal comfort for underground mining applications. An approach was developed in the form of a "comfort model" which applied comfort parameters to extensively assess the climatic conditions in the deep, hot, and humid underground mines.

Results: Simulation analysis predicted comfort limits in the form of required sweat rate and maximum skin wettedness. Tolerable worker exposure times to minimize thermal strain due to dehydration are predicted.

Conclusion: The analysis determined the optimal air velocity for thermal comfort to be 1.5 m/s. The results also identified humidity to contribute more to deviations from thermal comfort than other comfort parameters. It is expected that this new approach will significantly help in managing heat stress issues in underground mines and thus improve productivity, safety, and health.

Keywords: maximum sweat rate; skin wettedness; thermal comfort models; tolerable worker exposure times; underground mine environment.

Fig. 1

Sweat rate analysis as a function of air temperature, air velocity, and relative humidity at M = 200 W/m². The air temperature requirement to achieve the maximum sweat rate decreases by increasing the air velocity.

Fig. 2

Decrease of maximum allowable comfort temperature as a function of relative humidity at the metabolic rate of (A) 200 W/m² and (B) 300 W/m².

Fig. 3

Maximum worker exposure analysis as a result of increasing metabolic at an air velocity of 1.5 m/s and relative humidity of (A) 60% and (B) 80%.