Zones of a luminous flame

The luminous flame has four zones namely:

  • Dark zone/ zone of un burnt gas; burning of the gas does not take place here, it is dark and cool.
  • Luminous yellow zone; the gas burns in this zone but not completely because of limited air. Tiny particles glow in this region to give out light.
  • Thin outer zone; the zone is colourless and gas burns completely due to plenty of air.
  • Blue zone; this zone receives plenty of air and burning is more complete than in luminous zone.
    Non luminous flame
    This is the flame produced when the air hole of the Bunsen burner is open. Air enters through the air hole and mixes with the gas. This makes the gas to burn completely producing a very hot flame used for heating. The flame does not produce soot. Examples of non luminous flame include; gas cooker fame and stove flame.


This type of flame has three zones namely:

  • Dark zone/zone of unburnt gas; the zone is dark and the gas does not burn. It is therefore cool.
  • Blue-green zone; the gas here burns but not completely due to insufficient supply of air.
  • Purple/pale blue zone; burning of the gas take place completely as there is plenty of air, making this region very hot.
    Differences between luminous and non luminous flames

Similarities between luminous and non luminous flames

  • Both flames have the dark zone (zone of un burnt gas)
  • Both flames have luminous zone where the gas do not burn completely. In this zone, the carbon particles glow to give out light.
  • Both flames have the non luminous zone where gas burns completely.
    Strike back
    Strike back occurs when the gas burns at the inner point jet or at the air hole instead of burning at the top of the chimney. It occurs normally when the air hole is left open when lighting the Bunsen burner. Strike back can cause explosion leading to destruction of property and lives.