testing for gas

Been in Mansfield for a week doing an electrical course and staying a few hundred yards away from Nottinghamshire's highest point - Silver Hill.
At the top is this statue to the memory of all the miners killed in Notts pits over the years.
On the back is a list of about 50 pits closed in Notts.

The coal was deep and hard to win, but it was hard coal with a high calorific value - nowadays we are importing coal from eastern Europe. The pits have been turned into nature trails.

Think about the carbon footprint of that wonderful strategy.