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A safety lamp is any of several types of lamp, which are designed to be safe to use in coal mines. These lamps are designed to operate in air that may contain coal dust, methane, or firedamp, all of which are potentially flammable or explosive.

Contents 1 First Safe Lamps 2 Early Illumination 3 Modern Lamps 4 See also

The best known early safety lamps are the Davy lamp, invented by Sir Humphry Davy and the Geordie lamp, invented by George Stephenson. Both of those were invented in 1815 and were later superseded by the Gray, Muesler, Marsant, and other lamps; most later lamps are constructed on the principle discovered by Davy, that a flame enveloped in wire gauze of a certain fineness does not ignite firedamp. Both the Davy and Stephenson lamps were fragile and gave very poor illumination however. The gauze in the Davy quickly rusted in the moist air of a coal pit, and so became unsafe, while the glass in the Stephenson was easily broken, and could then allow the flame to ignite firedamp in the atmosphere. Later designs tried to overcome these problems by using multiple gauze cylinders, but the glass remaned a problem until toughened glass became available. The problem of low illumination was not solved until battery-powered lamps were introduced, and gave rise to nystagmus, an eye affliction.

Prior to the invention of these safety lamps, miners used candles with open flames or phosphorescent sources of light (such as rotting fish). Later, barometers were used to tell them if atmospheric pressure was low (in which case more methane seeped out of the mine into the air). The use of small mammals or birds was used much later to warn of the presence of the deadly carbon monoxide present after underground fires or explosions, the so-called afterdamp. Such animals are much more susceptible to the gas, and will die before a human, so giving an early warning of the problem. An alternative method of removing the methane involved igniting the gas deliberately to cause explosions, thus evacuating the mines of the majority of explosive or easily flammable material present.

Nowadays, safety lamps are mainly electric, and traditionally mounted on miners' helmets, sealed to prevent gas penetrating the casing and being ignited by electrical sparks.

• List of light sources

Lighting and Lamps v • d • e
Incandescent:	Conventional - Halogen - Parabolic aluminized reflector (PAR)
Fluorescent:	Compact fluorescent (CFL) - Linear fluorescent - Induction lamp
Gas discharge:	High-intensity discharge (HID) - Mercury-vapor - Metal-halide - Neon - Sodium vapor
Electric arc:	Arc lamp - HMI - Xenon arc - Yablochkov candle
Combustion:	Acetylene/Carbide - Candle - Gas lighting - Kerosene lamp - Limelight - Oil lamp - Safety lamp - Petromax
Other types:	Sulfur lamp - Light-emitting diode (LED) - LED lamp (SSL) - Fiber optics - Plasma - Electroluminescent wire

This article incorporates text from the public domain 1907 edition of The Nuttall Encyclopædia.