Looks llike a fogger to me.

here are some current units:
http://bugsource.com/cyclone_fogger.html

and here is one that looks to be your unit:
http://www.domyownpestcontrol.com/fogmaster-micro-jet-ulv-fogger-7401-p-156.html

Ron wrote:
Found this in a old barn.

I think it's a heater, when you turn it on it blows (powerfully)
lukewarm air from the three openings.

It could be broken so it's not blowing hot air, but if it is a
heater,
what is the reservoir for?

http://i126.photobucket.com/albums/p...IM002035-1.jpg

http://i126.photobucket.com/albums/p...IM002037-1.jpg

http://i126.photobucket.com/albums/p...IM002036-1.jpg

http://i126.photobucket.com/albums/p...e/IM002038.jpg

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Keep the whole world singing . . . .
DanG (remove the sevens)