First sprinkle a generous layer of baking soda in the bottom of your oven. I started with 1 cup but before it was all said and done I used the whole box. But like I said, this was a nasty job. You probably only need 1 cup because you clean your oven often. After the soda is spread spritz it with water from a spray bottle. Then leave it for an hour or more. Every once in a while or whenever you remember, spray with water again. You want the soda moist but not wet. If it's wet, sprinkle more soda on. Keep spritzing with water for several hours (again, once an hour or two), you can even leave overnight like I did. You can even cook dinner with this mess in your oven like I did.
After about 8 hours or so, you can wipe the soda out. Now, I was going to be all technical and Google why this works so I could look smart. I did find something about the soda and carbon but the truth is. I don't care why it works. It's cheap, requires very little elbow grease and is easy. 'Nuff said? Good. Now do not go be all clever on me and try to scrub your oven clean after the first hour. It won't work. Ask me how I know. You have to let the soda do it's job.
Now here is what my oven looked like after I wiped all the soda out. Much better but I thought it could be even better. So I took my favorite tool in the world, my handy dandy Pampered Chef stone scraper thingy and applied the smallest amount of elbow grease to get the rest of the gunk out.
And ended up with this. Which I was pleased as punch with until I put my pictures on Photoshop and saw all the yellow gunk on the front walls. But hey, the cookies don't complain about dirty facilities and the nachos seemed satisfied with their accomodations as well so we'll call it a day.
There you go, fume free, cheap way to clean your oven.