If you just want to warm your person you want to get "radiant" or "infrared" heat, these work very well for that, but again only in well ventilated areas.
I use one when working outdoors. The point is, if you're trying to heat a large space it takes a lot of btu and you will need ventilation free btus, but heating just your person with adaquate ventilation makes it easier (and cheaper)
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I have the dual version of this heater. Was using it last weekend in my 500 sq ft garage and my wife commented on the fumes when she came in. I try to run it for a couple of hours to heat up the garage, then turn it off for an hour. I use this cycle to try and maintain the heat when I am working. The process works pretty well, but having the uninsulated walls it cools down too fast.