In the old days of shallow drinking wells on farms, it was well known that one could suffocate from gas in the well.
Experienced workers would always go down with a rope around them and a competent worker to pull them out.
These were 30 and 50 ft. wells.
So methane is where you find it.
What do you think the old days of the canary in the coal mine was all about?
Tree hugger scare tactics is what it is all about.