My microwave is also a convection oven. I hadn't used it in about 10 years (the oven function). When i did after about thirty seconds there was smoke/steam coming out of the thing. On GE's website it says this is normal. That doesn't seem normal to me. My microwave is pretty clean but i could see splatter and whatnot getting into the vents over time and there is no real way to clean that. Perhaps it was burning that stuff off? Anyways i stopped using it immediately and stuck to my toaster oven
GE link
http://products.geappliances.com/appliance/gea-support-search-content?contentId=19303
