I’ve seen a few people put their delivered pizza in the oven after everyone grabs a piece to keep it warm. I’ve also seen a lot of those people forget the pizza is in there and either have to throw it out or only noticed after they preheated their oven.
Cardboard burns up pretty quickly. I would think the fire would be contained in the oven no?
Last time I set an oven fire there were flames licking up and out of the vents on the top, along with a lot of smoke. I wasn’t sure if opening it to get the flaming nachos out would give it more oxygen and bigger flames. It did not, but I had the fire extinguisher ready when I opened the door.