The importance of air quality in coal mining

J.W. Schmode, Polar Mobility Research, Canada, provides an insight into the importance of health and safety in coal mining, and offers a range of solutions to help improve air quality.

The first priority and concern for everyone, in any industry, must be the health and safety of its most precious resource and asset – the employees. This year being 2020 has been a very interesting adventure, with all that is going on in the world; the public is inundated with multiple sources of good, as well as misleading, information regarding everyone’s health and well-being.

The risk of ignoring the health and safety of employees is just too high. The future liabilities could be massive if employers do not take precautions and use the most up to date technologies to protect their people in the present. So, knowing that, employers should do everything in their power and use the latest known technology to reduce the risk of damaging people’s first line of defence.

Ok, so what is the first line of defence? What is the first and foremost requirement for you to live? It is not food or water, it is in fact the respiratory system!

The basics of any medical exam or consideration regarding the health of a person starts with, “Can they breathe?” It is the first thing people are told to check in first-aid training. That being said, everyone’s first priority should be protecting and taking care of their respiratory system. All other bodily functions stop, die or cease to work if oxygen cannot get into the bloodstream; and it is only possible for oxygen to get into the bloodstream through the lungs.

Having healthy strong lungs means a healthier longer lasting body and greater resistance to biological and environmental attacks against you. The majority of people who do not recover from viral infections, such as the coronavirus, had a pre-existing health issue that could possibly be traced back to prior respiratory-related damage to their body or immune system.

The dangers of air pollution in the construction industry

There is a risk of respiratory illness that exists, which is caused by exposure to airborne particulate and exposure of harmful ‘carcinogenic dust’ particulate in the workplace that can cause respiratory disease. There can be millions of airborne particles in the air being breathed in by workers. Crystalline silica, asbestos, diesel particulate matter (DPM) and coal dust all become respirable size particles when workers chip, cut, drill or grind objects in construction and mining. As a result, these particles can, and will, be inhaled.

Many of the larger particles escape the body; however, the small sharp ones and the DPM, in many cases, do not leave the body. Lung disease caused by the inhalation of crystalline silica dust and asbestos fibers are marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs and is a predisposing factor for bronchogenic carcinoma and malignant mesothelioma.

Inhaled mineral and coal dust progressively build up in the lungs and cannot be removed by the body. DPM, a known human carcinogen, is a significant concern since the particles formed are virtually all submicron nanoscale particles in size; have virtually no inertia at these small diameters, can linger in the air and easily penetrate into the lung tissue and then blood.

Lowering the concentration of harmful respirable particles in the air that people breathe is the most effective means of preventing diseases caused by excessive exposure.

Research on air quality

Whilst an enclosed cabin on a fixed or mobile plant provides some protection, there is a proliferation of field studies that clearly depict that the internal cabin environment can be more harmful than the external environment outside of the cabin.

These studies have been completed around the world by occupational health and safety regulators and authorities, universities and the industry itself – not only in regard to particulate and fiber exposure, but also in relation to other environmental factors such as carbon dioxide (CO2) concentration (which can lead to fatigue and drowsiness), enclosure pressurisation, recirculation air filtration, etc.

If an enclosure HVAC system is operated on 100% recirculation air and/or if the external filter is blocked or plugged, then CO2 concentration will increase quickly which will cause sleepiness, loss of concentration and alertness, fatigue and acidosis. A positive enclosure pressurisation is paramount; negative pressurisation will actually draw in particulate.

The goal should be to create an atmosphere of clean breathable air to the employee to keep them alert and to deflect and protect them from harmful respirable particulates and bio-aerosols. First and foremost, being in an enclosed office, meeting room, lunch room or operator enclosure may seem like you are protected; however, you could be safer just being outside in a slight breeze.

What are the options for quality air solutions?

First, an enclosure should be ‘air filter pressurised’, somewhere in the range of 0.1 – 0.5 in. of water column or 25 – 125 pascals above the ambient pressure at that elevation, which should keep particulates out. Anything above that pressure is not recommended as it may cause harm to a person’s ears. Enclosures do require some air leakage to release CO2 and bring in oxygen; being sealed too tight is also not good.

With the installation of a good enclosure pressuriser and filter system, a dirty enclosure is often cleaned up significantly. In addition to a system, employees and operators should be trained to brush off their clothes and boots before entering their filtered air enclosures in order to try and increase their health and safety.

When talking about filtered pressurisation and dealing with crystalline silica, asbestos, DPM, coal dust and now bio-aerosols, one should use high efficiency particulate air (HEPA) filtration rated for nanoparticles. Some call this Ultra HEPA. A minimum efficiency reporting value (MERV 16) rated air filter may be just fine when DPM and bioaerosols are not present, but if they are, Ultra HEPA is necessary.

First of all, a HEPA filter should be rated in filter classes defined in ISO 29463 and EN 1822 Standards. H13 or ISO 35/40H is the starting point to capture DPM and bio-aerosols. The size does also have to be calculated as velocity and air volume can change efficiency. Secondly, the air inside an enclosure should be processed, cleaned and disinfected constantly. Air purification re-circulation systems are recommended to be used with heating ventilating and air conditioning (HVAC) systems.

A downdraft system is the most efficient system as the contaminated air is pulled from the floor or lower area of an enclosure and then processed while the clean air is returned above the occupants of the enclosure. However, if this is not possible, any air purification recirculation system is far better than nothing.

Air quality equipment – Bio-aerosols

When it comes to bio-aerosols like viruses, bacteria, spores and mould, there are other air purification options to consider.

Ultra HEPA air filtration
With efficiencies of 99.978% or better with particles of 0.3 microns or smaller, a virus in the corona family can be 0.06 – 0.14 microns in size and will only be airborne when attached to a larger part. An Ultra HEPA or nanoparticle filter should be able to trap most of it.

Ultraviolet light – germicidal irradiation (UVGI) The ultraviolet (UV-C) wave spectrum, 180 – 280 nanometers, damages the ribonucleic acid (RNA) of a virus and can also damage and kill the deoxyribonucleic acid (DNA) of bacteria, spores and mould.

According to the American Council of Governmental Industrial Hygienists and other sources, upper air disinfection of bio-aerosols by UVGI is close to or equivalent to 20 air changes per hour, providing substantial protection against airborne biologicals.

Anti-microbial heat exchangers
Copper, and more specifically anti-microbial heat exchangers that are copper, have been researched and reported to kill biologicals such as the bacteria that causes legionnaire’s disease, staphylococcus, Middle East respiratory syndrome (MERS) and the swine flu (H1N1), as well as coronavirus 229E, a relative of the COVID-19 virus, that causes the common cold and pneumonia.

Copper has a free electron in its outer orbital shell of electrons that easily takes part in oxidation-reduction reactions, thus preventing cell respiration and punching holes in the cell membrane or viral coatings. This can destroy the DNA and RNA inside a bacteria or virus. The Environmental Protection Agency (EPA) has registered copper surfaces as being antimicrobial.

Bipolar ionisation/corona discharge
These are reactive, positively charged hydrogen ions in the air that react with airborne contaminants, including viruses. This is preferred over an ozone generator which can do a similar function, however ozone concentrations above 10 ppb can be harmful.

Ozone generators
Ozone (O3) is a reactive gas that can disinfect air and surfaces by killing viruses, bacteria and fungi. They should only be considered for disinfection on unoccupied spaces; it should never be used in occupied spaces.

Conclusion

Maybe this is something you have already read or known about some, or maybe this is new information. Either way, employers should be encouraged to do some fact checking of their own to see how protected they and their employees are at work when it comes to the air being breathed and what is in it.

There are many professional companies out there that do air quality testing, heating and ventilation upgrades, modifications and installations of systems that help you obtain cleaner air for your body’s first line of defense.