In reply to Brown:
Indeed, but the salesman was very insistent this was not the case.
He had a very slick presentation on the benefits of their system, and wasn't prepared to deviate.
Kept telling me it was to do with the construction and special materials their heater was made from, etc., even when it was clear I had some knowledge of what I was talking about.
It's quite possible he wasn't scientifically literate enough to understand that the spiel he was giving was bollox, but presumably someone with understanding had told him to say it.
I'm posting here because I think it could be very convincing if you don't have a scientific background.
Also, he mentioned keeping elderly people warm a few times, giving me the impression they might target the elderly.
Is there a route to report such dodgy selling?