I like this style of heater. It's vented but uses no electricity. I had a similar model in a motorhome I owned in Europe. No need for a blower in a small space.
http://www.amazon.com/Home-Comfort-...3393597&sr=8-8&keywords=vented+propane+heater
http://www.amazon.com/Home-Comfort-...3393597&sr=8-8&keywords=vented+propane+heater