© Science Museum Group, London
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| Above & below: Davy lamp with clearly visible dents. © Science Museum Group, London |
Falling rocks or coal were not the only causes of accidents; mine explosions continued to occur. One reason for this was that mines, which had previously been closed due to the danger of gas, were reopened because it was believed that they would be safer with the Davy lamp (Hubig 1983: 27).
However, the safety of the lamp depended on several factors:
Air currents of more than 1.5 m/s could cause the flame to strike the mesh, causing it to glow. In certain underground areas, this airspeed was often exceeded, increasing the risk of accidents.
Improper use of the lamp also posed a danger. For safety reasons, the Davy lamp had to be lit above ground and then carried burning down into the mine. It was forbidden to relight the lamp underground, but this still occurred, which increased the risk of explosion. Later, the lamp was equipped with a screw closure.
Additionally, miners sometimes made holes in the mesh cap due to the low light intensity, which also increased the risk of accidents.
The Davy lamp was also known as the 'firemen's lamp' because shot-firers would unscrew the lamp to use the flame to light the fuse for dynamite. When the Davy lamps were equipped with closures, they could no longer be unscrewed. Shot-firers then pressed the fuse against the mesh, causing dents. This is a particular characteristic of the Davy lamp, as the images on the right show.
(Hubig, Peter: 160 Jahre Wetterlampen, Essen, 1983, p. 27)