Were They That Safe?
The terrible toll taken of underground coal miners in the 18th century lead to public outcry and a search for safer means of mine lighting, the outcome of which was the development of the Flame Safety Lamp.
Such lamps are generally considered to have been a boon to miners, and to have lead to a dramatic reduction in underground explosions and fires. While undoubtedly many lives were saved by the use of flame safety lamps, they were far from safe.
Careful review of the excellent compendium of mining disasters in the UK located at http://www.dmm.org.uk records 482 mining disasters between 1705 and 1999. The list is far from a comprehensive accounting of the tragedies, understandable considering the difficulties of collating the accident record, but it does provide a useful starting point.
Only those disasters resulting in the deaths of 5 or more people are listed, and many incidents are not known in detail. The total toll was nearly 15,000 men, women and boys, and by far the biggest killer was explosion or fire. The graph below records the death toll.
Deaths resulting from major accidents (+5 fatalities) n UK coal mines by decade ('01-10) between 1710 and 1980. The black line shows total fatalities, the blue line fatalities due to flame safety lamps (after Durham Miners Museum website, 2003)
Fully 25% of the disasters are recorded as being caused simply by an explosion, and 21% were recorded as being caused by the use of naked lights or contraband. Undoubtedly, many of the disasters for which no cause of the ignition is stated were the result of naked lights igniting methane / air mixtures.
Between the date of the first public demonstration of a working flame safety lamp in December, 1815 and the outbreak of World War 2 in 1939, when electric lamps slowly began to be widely used, about 12,800 died in explosions in underground coal mines. Almost 20% of these deaths, 2350 in all, were attributed to ignitions caused by flame safety lamps. Not only did they kill, flame safety lamp ignitions killed nearly twice as many per accident than as any other cause.
Nevertheless, the facts bear witness to the truth - flame safety lamps were far from safe, a fact that was known at the time as a result of many investigations in both Britain and Europe. Unfortunately, until the development of electric lamps, the Flame Safety Lamp was the only alternative to the naked flame.
Perhaps the last disaster attributed to the use of flame safety lamps occurred in Australia at the Moura Colliery on July 16, 1986. Twelve miners were killed in an accident that has also been linked to the auto-ignition of a methane / air mixture suddenly compressed in a major roof fall. Although this alternate explanation has been shown to have some validity in theory, it has not yet been proved as the actual cause of the disaster. Following this incident, flame safety lamps were banned in New South Wales.
Modern methane detectors are designed in a way that prevents them from igniting flammable gas (intrinsic safety). Many coal mining areas have abandoned flame safety lamps in favour of such instruments, which can also detect, and in many cases record, levels of oxygen, carbon monoxide and hydrogen sulphide found in some coal mines.
Although many jurisdictions still require the use of flame safety lamps for gas testing, there is no doubt that their use is diminishing, and that their heyday is long since past.