Can tubular heaters be mounted vertically?

[Percyprod]

As in title, can a tubular heater be mounted vertically? Doesn't sound like a good idea to me, but it would settle an argument if some one could answer.

 

[123]

Just don't mount it upside down, the heat will sink not rise

 

[littlespark]

Keeping a mince pie warm?
Hummmm

You think you could use one to cook the turkey..... from the inside out