"but imposes that duty on every other employer in the country."

Not quite all - prison screws aren't covered.
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"odd situation where tobacco smoke is banned but 'alternatives' aren't" - not so odd. In Irish pubs, I understand, herbal cigarettes aren't covered by the ban, so long as they don't contain tobacco. Of course one popular herb is affected by other legislation...

The English ban covers all types of smoking - though I don't think it applies to incense in churches, so long as it isn't polluted with tobacco.