A few words about gas works. The sites are easy to find, many are still brownfields because of the cleanup costs. A search of a superfund list for a given state reveals them. Always adjacent to the railroad tracks, for access to coal supplies, and oil for the "carburetted coal gas" process. These facilities were remarkable efficient, using virtually all of the coal for profitable purposes. Even the byproducts were used, aspirin is a coal tar derivative, for example. Don't confuse efficient with clean, however, what little was left was REALLY bad stuff, containing things like dioxin. Dig at the site of a former gas works and you smell moth balls from residual nathalene. Not much of this sludge was left over, so most just buried it on site, hence the contamination. I lived in Worcester, MA when they tore down the gas works, which was a big one. Seeing inside gave me the feeling that I was lucky not to have had to work there. Later I lived in Trenton, NJ, and the gas works site on Brunswick Ave. was a large brownfield with a double chain link fence around it. Natural gas and early environmental regulations made producer gas unprofitable, in the US most closed in the 1940's, although they were usually just abandoned, to be torn down later. As has been said, the gasometers were just as useful for storing natural gas and so are still in use in some places. One example can be seen in the opening of The Sopranos.
Safe and effective when used as directed