In an underground ventilation system where there is a change in the moisture content of air, sigma heat is useful to identify and quantify the heat transfer processes. The literature on psychrometry suggests that the sigma heat is a function of barometric pressure and wet-bulb temperature. However, a direct expression of this relationship has been elusive. This paper presents a direct and straightforward expression for sigma heat as a function of wet-bulb temperature and barometric pressures within the range generally encountered in the underground mine environment. Also, a direct equation for wet bulb temperature as a function of sigma heat and barometric pressure is presented, which otherwise require lengthy calculations involving iterations. The difference between calculated and predicted sigma heat and wet bulb temperature is within +1.32 kJ/kgda and -1.39 kJ/kgda; and +0.28 °C and -0.64 °C, respectively. The efficacy of these prediction equations is quantified with some examples involving the performance parameters of cooling tower and spray chambers. Moreover, a psychrometric chart with sigma heat as a parameter in place of enthalpy is produced with the help of MATLAB code and presented in this paper. 

Experimental sampling of diesel exhaust nanoparticles using a Naneos Partector 2 instrument has been conducted in an underground polymetallic mine. This sampling was conducted within 12 minutes in the operator open cabin of the mine face LHD loader R1700 (engine model Cat@C11 ACERT, 241 kW, Tier 3/Stage IIIA Equivalent Engine) working in the active ore heading area. The aim of this experimental sampling was to determine the exposures of the cabin operator to diesel exhaust nanoparticles. The LHD loader operated in a 70 meters length drift (4.3x4.2m), where the auxiliary ventilation velocity was around 0.5 m/s. As a result, the averaged data for Lung Deposited Surface Area (LDSA) and diameter were 7 470 µm²/cm³  and  90 nm, respectively. The results of this study suggest that Naneos Partector 2 sampling instrument can be employed in polymetallic mines for monitoring workplace surveillance. This study offers important data on particle surface area. As the surface contact between the particles and human cells is crucial, particle surface area might be a new approach to investigate particle toxicity.

Coal dust causes a range of diseases and health problems worldwide, such as Coal Workers' Pneumoconiosis. Numbers of static studies showed that surfactants could increase the coal dust wettability effectively in water spraying. However, coal dust does not remain in a static state in underground mines. Therefore, studies should be conducted in a dynamic state where coal dust and surfactant droplets will get a shorter contact time. In this study, wind tunnel tests have been conducted to capture the dynamic process. Logistic regression modelling has been done to evaluate the suppression performance in terms of efficiency and quantity of dust suppressed with respect to three dependent variables: surfactant types, surfactant quantity and coal dust concentration. The results showed that at low coal dust concentrations, the suppression efficiency is greater compared to high dust concentrations. Moreover, the surfactant quantity of 0.05% to 0.20% is more efficient than above. Although the surfactant type did not emerge as significant when low and high dust concentrations were combined, it becomes significant at low dust concentrations where SDS and CTAB are more efficient than SDBS and TX100. The results will help in selecting surfactants with the appropriate quantity in different coal dust concentrations.

The COVID-19 pandemic has certainly shocked the world and made everyone to rethink, rework and reimagine the workplace of tomorrow. The 21st-century engineer will have to work smarter to manage the changing environment and employ technological tools to aid them in the quest for zero harm.
This paper outlines the concept of remotely and autonomously supplying ventilation to underground workings, commonly referred to as Ventilation-On-Demand (VOD). 
For ease of reference, the presentation refers to VOD. However, the proposed system should rather be viewed as a Ventilation Optimisation Solution. Through remote monitoring of working conditions, these systems can be used extensively to improve workplace conditions ,whilst offer financial benefits.
This is made possible by employing sensors for real-time monitoring integrated with hardware to address sub-standards in real time.