For removing light odors, we recommend to air it out. Just leave the door open for couple of hours. Or else, you can place a bowl of baking soda in the oven for an hour. This will absorb smell and leave it refreshed. However, if there are strong odors like burnt food or popcorn, you have to first clean any leftover residue. Now you can place any odor absorbing items like salt, baking soda, activated charcoal or any other until you use the microwave oven again.