But another question arises, how do you find the "tiny little LED" in
a dark mine?

My fire detectors in my house have a little 9V battery and those LEDs flash
for many months. Flip a switch and a tiny LED could shine for weeks.

To answer Dean's question, it has to be really easy to pass the 'explosion'
test for LEDs - again, this is from someone who just 'plays' with LEDs as a
hobby. But the 'working bit' is exclosed in a tough plastic unlike those
flash lights although I'm sure they are ruggadized. Perhaps the best bet
would be to many a really tiny headlamp and put it on a canary.

I think an hour's thinking could come up with many options, each one better
that the situation we have now with six (hopefully alive) miners in 58F
temperatures in darkness.

Oh well, just a thought.

Hilton