[NeedMoreTea]

I'm really surprised - and a little impressed - that one hung on that long. :)

From various encounters over the decades they all seemed to come with feint smell of burnt dust or just dust. By the eighties it was usual to see a radiator in front of or above the old vents, or the vents simply boarded or painted shut.

No idea why it was so comprehensively and quickly rejected despite that brief popularity. Maybe the impossibility of proper cleaning or expense? Though I wonder what they do for cleaning in the US. It's the only approach that hasn't managed to keep some spot in the market even after large declines - like storage heaters or, more surprisingly, even coal have.