It is important to store a fire extinguisher in your kitchen, since this is the most likely place for a fire to start. You want to be able to access the fire extinguisher quickly if a fire starts in your oven. Once you use your fire extinguisher to put out the fire, you will be left with a big mess. Cleaning up isn't hard, though, if you follow the proper procedure.
Put a mask over your face. Then slide on a pair of plastic gloves. Remember that you are about to clean up a chemical. It may not be toxic, but the chemical can cause irritations that can be avoided by wearing a mask and set of gloves.
Attach a hose to your vacuum and vacuum up the dry powder inside of the oven.
Use a dustpan and brush to get up any dry powder spots that were not immediately removed by the vacuum cleaner. Once these spots are loose, you can vacuum the area one more time.
Wet a sponge and wipe the oven down completely. You may have to stop and rinse the sponge out a few times. Almost all of your fire extinguisher mess should now be cleaned up.
Spray oven cleaner in your oven. Follow the specific oven cleaners instructions. The oven cleaner will pick up any left-over residue, and give your oven a good cleaning so that it will be ready to cook the next meal.