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22 January 2009

Safety Candle

Every year in Australia people die and many homes are destroyed because of these: candles.

A naked flame will set fire to things very easily and if the candle falls over that's often what happens.

But it needn't. All we have to do is make use of a simple device invented nearly 200 years ago, and this is it, a mesh of metal screen.

This one's simply made out of insect wire, bronze so it doesn't melt.

It was the discovery of Humphry Davy that flame doesn't penetrate mesh.

You can see here that it goes up to the mesh, spreads below it and even makes the mesh red hot but it won't go through. Davy used the principle to invent a safety light for miners.

Candles in a mine would ignite dust, like this, called mine gas, causing an explosion or a fire.

Davy enclosed the candles in mesh and the problem was solved.

And this is how effective it is.

A candle sets fire to paper easily but through mesh, even though the paper may eventually char, it doesn't catch fire.

Even inflammable liquids don't catch fire although they touch one side of the mesh and flame touches the other.

Take the mesh away however and they burn fiercely.

This torch burns inflammable gas rather like mine gas. If I blow it out a flame will easily reignite the torch again. But, through the mesh, even though the gas is burning inside the mesh tube the flame can't get back to the torch and light it there just as the safety lamp stopped the candle from setting fire from the mine gas.

Davy's discovery helped miners nearly 200 years ago. Today coal miners use electric lamps but those of us who still use candles can profit from Davy's discovery and keep our houses safe.