I used to use a salimander heater in my 900 square foot shop. The fumes from the salimander aren't good for you. My carbon monoxide detector would go off 20 to 30 minutes after the salimander was turned on. My shop is insulated tight enough so the temp seldom goes below 40 degrees...only heat is from my Suburban. Last week I did purchase this heater for my shop:
http://www.mrheater.com/product.aspx?catid=50&id=180
They do have a smaller one:
http://www.mrheater.com/product.aspx?catid=50&id=180
I hope to have it installed in the next week or two depending on when my future Son-In-Law has time (He is a HVAC guy) and how soon I can get a propane tank installed. I have 2 Cubs, 3 moldboard plows of my own to restore and possible few Cubs and motor(s) to restore/rebuild.
Do yourself a favor-
get a well vented heating system installed in your garage or shop. Your life may depend on it.