Davy's Safety Lamp: How Does it Get Oxygen to Burn in Coal Mines?

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Hi there!
(It's not actually a homework question)
I just wanted to ask where does the lamp get oxygen to burn on in coal mines.
So there must be an inlet for air. Of course it is explained in my book that as the wire mesh distributes the heat therefore the temperature does not rise to the ignition point of the methane in coal mines.
What i don't get is ,there must be a source of air for the lamp(cuz you don't carry an oxygen cylinder for it).And it must reach the flame and if it contains methane it would burst right away(??)
I just can't get a completed picture of it.I know there must be some reason because it's practically possible.

 

[mathman]

The mine is open to the outside world. Remember that the miners need air to breath.

 

[Equate]

Hi there!
(It's not actually a homework question)
I just wanted to ask where does the lamp get oxygen to burn on in coal mines.
So there must be an inlet for air. Of course it is explained in my book that as the wire mesh distributes the heat therefore the temperature does not rise to the ignition point of the methane in coal mines.
What i don't get is ,there must be a source of air for the lamp(cuz you don't carry an oxygen cylinder for it).And it must reach the flame and if it contains methane it would burst right away(??)
I just can't get a completed picture of it.I know there must be some reason because it's practically possible.

The screen acts as a flame arrestor; air (and any firedamp present) can pass through the mesh freely enough to support combustion, but the holes are too fine to allow a flame to propagate through them and ignite any firedamp outside the mesh.

http://en.wikipedia.org/wiki/Davy_lamp

 

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Thank you all for your help!