If you use your house oven to cure shirts, chemicals may be released that could very well be harmful to you, since you prepare food in there as well.
You should get an iron that has very high temperature settings, and just iron the designs that you screenprint for 2 to 3 minutes. You may want to lay a piece of paper on the design while you iron it otherwise the iron may smear the ink before it's set and that looks pretty bad (it's happened to me a couple times). Also, what I do instead of using a piece of paper, I flip the shirt over and iron from the back for a half minute or so, that way it heats up the front enough to set the ink so that it won't smear when I iron on it directly.
If you see 'smoke' rising up while you're ironing, don't worry, that's the water from the ink evaporating (if you're using water based ink, that is), so the steam/smoke is a good thing.
As you expand, you may want to consider more professional methods of curing. Check the link that Rodney posted for information on the different ways.
And Rodney, glad to see that an old post that I started had so much discussion and helps other people
house oven for drying 
