A good ventilation system consists of a way to expel the air around the torch area to the outside, and a source of clean make-up air. Depending upon the size of your room, the location, (enclosed basements are not a good place) and the number of windows you have, you will need to find a way to make sure that you are getting all of the bad air out of your space so that you don't breath it in.
When I was setting up my first studio in Ohio, I ended up setting it up in the front room of our house! I realized that the basement would not work because I would be too close to the furnace and I no good source of makeup air. I found a good scratch and dent range hood on ebay that had a 360CFM fan that we hung over my table. This was vented out through the window along with the propane hose. When I torched, I opened up the dining room windows so that I had a good source of fresh make-up air. This worked very well.