page_title: Safety lamp
section_title: Davy lamp
hierarchical_section_title: Safety lamp / Oil lamps / Examples of lamps / Davy lamp
caption_attribution_description: English: en:Davy lamp, a safety lamp for use in coal mines
context_page_description: A safety lamp is any of several types of lamp that provides illumination in coal mines and is designed to operate in air that may contain coal dust or gases, both of which are potentially flammable or explosive. Until the development of effective electric lamps in the early 1900s miners used flame lamps to provide illumination. Open flame lamps could ignite flammable gases which collected in mines, causing explosions and so safety lamps were developed to enclose the flame and prevent it from igniting the surrounding atmosphere. Flame safety lamps have been replaced in mining with sealed explosion-proof electric lights.
context_section_description: In the Davy lamp a standard oil lamp is surrounded by fine wire gauze, the top being closed by a double layer of gauze.
  If firedamp is drawn into the flame it will burn more brightly and if the proportions are correct may even detonate.  The flame on reaching the gauze fails to pass through and so the mine atmosphere is not ignited.  However, if the flame is allowed to play on the gauze for a significant period, then it will heat up, sometimes as far as red heat.  At this point it is effective, but in a dangerous state.  Any further increase in temperature to white heat will ignite the external atmosphere.  A sudden draught will case a localised hot spot and the flame will pass through.  At a draught of between 4 and 6 feet per second the lamp becomes unsafe.  At Wallsend in 1818 lamps were burning red hot (indicating significant firedamp).  A boy (Thomas Elliott) was employed to carry hot lamps to the fresh air and bring cool lamps back.  For some reason he stumbled; the gauze was damaged and the damaged lamp triggered the explosion.  At Trimdon Grange (1882) a roof fall caused a sudden blast of air and the flame passed through the gauze with fatal results (69 killed).
  Poor copies and ill-advised "improvements" were known, but changing dimensions either reduced the illumination or the safety.  The poor light compared to either the Geordie or Clanny eventually led to the Davy being regarded as not a lamp but a scientific instrument for detecting the presence of firedamp.  Some pits continued to use candles for illumination, relying on the Davy to warn men when to extinguish them.
caption: A Davy lamp
exif: {}