This mine was known for bad air!
When it was worked, frequently, they used to create a fire in a waggon, send it into the level, then pull it back, to help the ventilation.
Eric Bowman who worked there in the early 196o’s told me the Mining company had tried going down surface shafts, but found them all to be blocked!
When I was in there some 50 or so years ago, my wife tried to light a cigarette when we reached Williams Vein(?) and could. Not! She rapidly beat a retreat and I soon followed!