Mine ventilation in the COVID-19 Era

The South African Minerals Council indicated that the mining sector has special circumstance that could make it vulnerable to the transmission of infectious diseases such as COVID-19. It noted that employees congregated in areas of work and travelled in close proximity. As mining often involves physical activity, there could be a high degree of exposure to the virus simply through contact with people, machinery and equipment. Also, mining executives and officials who visit offshore operations were at risk of contracting the virus in other countries and bringing the infection into South Africa or spreading it to other countries.

The current, worldwide COVID-19 pandemic is having a significant impact on the livelihood of entire communities and on the viability of numerous aspects of the economy.  After several weeks of almost total shut-down of mining operations, a cautious and limited re-start of the country’s industries has been permitted by the South African Government.  Relaxation of lock-down measures in the workplace, recently legislated by both the South African Department of Minerals and Energy and the Department of Labour, re-affirm responsibilities of owners and operators in terms of the health and safety of workers.

The occurrence of COVID-19 hotspots traceable to places of work, or activities associated with these, may lead to operational stoppages. More importantly, the duty of care by Employers towards ensuring zero harm to all employees is being challenged in remarkable ways by this pandemic and requires the adoption of effective custom-designed preventative and protective measures.

Medical research has established that one of the mechanisms that the coronavirus, SARS-CoV-2 microbe, known as COVID-19, infects persons directly is by airborne droplets containing the virus.  The virus is transported in droplets produced when an infected person coughs, sneezes, or talks and may find its way, directly or indirectly, into the respiratory system of persons nearby. It has been postulated by some studies that the radius of direct transmission of infected droplets is 1.8m.  Direct contamination is through assimilation of airborne infected droplets into the respiratory system.  Indirect contamination is through hand contact with contaminated surfaces (where infected droplets would have been deposited by the air stream) and subsequent cross-deposition from the hands to areas near the mouth, nose and eyes – from where the virus may enter the respiratory system.

Although symptoms of acute COVID-19 infection are well recognised, and primary screening may identify infected (and therefore) infectious individuals, long incubation periods and asymptomatic carriers, who are known to represent a significant portion of the overall infected population, complicate the method by which the virus may be detected, enhancing the risk of human infection.  Transmission of the virus by asymptomatic individuals is particularly insidious and problematic within the confines of certain workplaces – particularly as studies are still being conducted to identify exact infection transport mechanisms and conditions associated with them.

Underground deep level mines have unique challenges in managing COVID-19 related infection spread.  The transport of personnel to and from underground workplaces involves rope winders and steel conveyances up and down the mine shafts.  Implementing internationally recommended social distancing fully in mine cages is not feasible nor economically viable as large numbers of workers must be transported to the workplace in a short space of time.

These mines are positively ventilated by circulating large volumes of air through the mine, meaning there will always be an airflow velocity present which will influence the fall-out and settling behaviour of saliva droplets and aerosols.  Mine cages experience various airflow scenarios depending if they are stationery or moving against or with the ventilation direction.

For mines to implement specific risk reduction actions regarding mine cages one must firstly understand the airflow patterns in mine tunnels and workings under certain scenarios, secondly the impact of airflow velocity on fall-out and settling behaviour of saliva droplets and aerosols, the settling and contamination of surfaces, and lastly attempt to combine the results to predict the virus transmission in the working places.  Once a reliable understanding is achieved then potential interventions to reduce the risk of inter-person transfer can be investigated.

Underground mining operations take place in constrained environments, if not in outright confined spaces.  Work places are ventilated mechanically, often in series with others, potentially increasing the risk of COVID-19 cross-contamination despite observing customary distancing precautionary measures.

In an effort to limit the risk of worker exposure to infection in underground mining operations, studies into the mechanisms through which droplets that typically may contain the COVID-9 pathogen are transported into defined mining environments by the prevailing ventilation systems are proposed.  Knowledge of these mechanisms will assist the identification of circumstances that may exceed the capacity of currently employed protective measures, possibly placing workers in an unduly higher risk of contamination.

Initial studies could be limited to aerodynamic and mining physical considerations affecting the movement of water droplets in the airstream.  Epidemiological aspects of the virus relating to temperature, air humidity, air density, transfer by touch and related aspects needs to be addressed once the impact of droplet spread due to ventilation is fully understood.

COVID 19 has changed the world very quickly and in order to still meet the needs of the mining industry the need to adjust and change manage the processes and services is inevitable, since the number of experienced ventilation practitioners have also greatly decreased over the past couple of years and many of the skills that were built into company hierarchies have left the industry.

The underground environment has a direct impact on the health, safety and productivity of the workforce and in response to these issues, BBE, the world leaders in mine ventilation and cooling systems, provides specialist ventilation and occupational hygiene services to the mining industry and assists mines by providing customised, appropriate and practical guidance that not only complies with all the legal requirements of the Mine Health and Safety Act, but also ensures a productive, healthy and safe work environment for the workforce.