Long story short, I remember reading somewhere the miners use a little birds the canaries

The bird flew inside the tunnel or they hold on with the bird. It is atrocious what they do to them.
At that time they did not have technology to detect the lethal gas that can escape from the earth.
I have a feeling it has to do with a man-made situation.
we are the only specie on earth that somehow destroy our own home.
Enough said!
Keep on steemit!