According to google, ammonia is not highly flammable, but it can explode when exposed to high heat. I think there are better ways to clean an oven than this.

Thank you graywings123 for taking the time to reply. For anyone else who may wonder about the same thing, I have since learned that today's ovens have electronic ignition so there is no pilot light to worry about.

So martae did you try the ammonia overnight? Did it work? My gas oven is deplorable and pretty new but I use convection for cooking meat a lot.

No cedelchef, haven't done it yet, but my daughter has done so with her gas oven and claims it works. I will try it after this weekend, and post my results.