On Sunday, 24 May 2015 09:06:38 UTC+2, Mike Collins wrote:

Things aren't always what they seem. When British Railways abolished steam
engines the monitoring station at what is now Salford University measured a
big increase in atmospheric sulphur dioxide because it was no longer being
absorbed by the activated charcoal in the smoke from the railway engines.

That's interesting!
I'm a fan of steam but must allow that they do have a bad image where dirt is concerned.
Not to mention the damage to health caused by mining the coal.
Do the old covered stations [and the tunnels of course] still accumulate thick layers of soot?
Do drivers and firemen still suffer from lung diseases?