For thousands of years, miners have confronted the challenges of creating adequate ventilation and air conditioning necessary to keep miners safe.
Adverse factors include debilitating heat, harmful dusts, oxygen deficiency and flammable toxic gases.
Early methods of ventilation relied mainly upon natural ventilation through adits and shafts, which were the singular means of entrance, access and transportation of ore. Short lateral tunnels known as crosscuts connected major workings and were also used for ventilation purposes.
Excessive gas buildups have occurred in areas inside a mine that lack adequate ventilation such as raises, winzes and dead ends. Underground gases including carbon monoxide, methane, hydrogen and nitrogen are often present in mines, though at varying levels. Many of these gases are difficult to detect because they lack color, taste and smell.
Georgius Agricola, a German scientist and father of mineralogy, discussed the challenges of mine ventilation in the 16th century with illustrated depictions of bellows, fans, linen cloths and shaft-head windsails in his book “De Re Metallica.”
Early means of detecting oxygen deficiency in mine workings involved candles and acetylene lamps. Oxygen content would influence the character of the flame in both height and vigor. However, this method was ill-advised under circumstances where combustible gases existed.
The rich copper sulfide ores found in the old stopes of Arizona metal mines have a history of spontaneous combustion of sulfide ore releasing sulfur dioxide from burning ore and carbon monoxide and carbon dioxide from burning wood.
Such was the case of the United Verde mines at Jerome that suffered continuous fires starting around 1897 and lasting several decades.
Men worked around these fires by using containment efforts that included sealing off of fire zones containing sulfurous smoke with bulkheads.
Studies undertaken in 1896 by Englishman Dr. John Scott Haldane that involved the use of canaries as a means of detecting the presence of poisonous gases in Cornish collieries (coal mines) would prove effective over the course of a century.
The Cross Mountain Coal Mine disaster occurred on Dec. 9, 1911, near Briceville, Tennessee. The flame of a miner’s lamp ignited explosions consisting of a combination of methane and coal dust that cost the lives of 84 miners.
Methane, a highly flammable and explosive gas, is most common in coal mines and is referred to as “firedamp.”
After that, Cross Mountain was the first mine in the United States to use canaries to judge the air quality in a mine.
When the birds began to show signs of drooping or shortness of breath, it was a sign for miners who lacked respirators to turn back or face suffocation. Hence the expression “canary in a coal mine” denoting an advanced sign of imminent danger.
Early 20th century techniques involving ventilation included the use of blowers or low-pressure centrifugal or propeller fans situated at the tunnel portal connected to a pipeline.
The Black Eagle and United American Mines located in the Oatman district of Arizona met the challenges of inadequate ventilation, including temperatures exceeding 103 degrees F.
The matter was resolved with the installation of fans to improve ventilation currents, including the No. 8 Sirocco, driven by a 25-horsepower motor delivering 31,000 cubic feet of air per minute, and two No. 5 Sirocco fans with high-speed blowers driven by five-horsepower motors down to the 1,250 foot level. The air was circulated through a 16-inch metal pipe.
Exhaust from internal combustion engines, including those of diesel locomotives, proved challenging, necessitating their exhaust be equipped with coolers, diluters and scrubbers to mitigate the amount of monoxide content rendered during tunnel construction.
Refrigeration became more common in some of the deepest mines during the late 1930s, including the Butte mines in Montana. They were installed at the surface near a water source. The water was circulated several thousand feet below to air-cooling units and then returned to the surface where its temperature was again reduced in cooling towers. The Magma Mine in Arizona used underground water for cooling; its refrigerating units operated below the surface.
Proper ventilation continues to be a concern in 21st century mining operations, with precautions toward the prevention of frictional heat and sparks caused by mining equipment along with the use of dust retardants such as crushed limestone and water.
Heightened regulations by the U.S. Mine Safety and Health Administration include the requirement that groups of miners carry proper gas-detection equipment.
Nanotechnology may also prove beneficial in detecting gases at the molecular level, further advancing improvements in mine ventilation.