Two is better than one. Mining at my fiat mine even when I'm not fiat mining. 
Discussion
How much heat do those put off? Enough to heat up a small desk area?
The little cubby I have them in is a little warmer than the ambient temp if I put my hand in there. But it's not really noticeable.
They do give off a whirring sound in the morning before all the other shit is up and running to mostly drown it out.
I'm in a machine shop so the air hoses and tool indexing making plenty of noise to mask it.
I gotta get one of these.