The oven itself won't necessarily catch on fire as long as there's nothing in the oven TO be ignited and as long as the door to the oven is properly closed. If a pan of food, or grease or crumbs of food are left in the oven then yes – a fire could be the end result.

What happens if you leave the oven on with nothing in it?

The oven itself won't necessarily catch on fire as long as there's nothing in the oven TO be ignited and as long as the door to the oven is properly closed. If a pan of food, or grease or crumbs of food are left in the oven then yes – a fire could be the end result.

How long can you leave the oven on with nothing in it?

As long as your oven door is left closed and your oven is not faulty or unreliable, you can leave your oven on for an extended period of time – twelve hours or more – without worry.