Q. If I came to a hotel that has an oven can I turn on the oven or do I have to be concerned that there are meat and milk drippings on the oven floor?

A. Horav Shlomo Miller’s Shlit”a opinion is that if you need to use a treif oven or microwave (when the kosher food is covered and properly insulated. See question 322 on this forum) you should clean first the oven from any unburned remnants of food. You do not have to be concerned for the imbedded (balua) meat and milk absorbed in the inner surfaces of the oven. Additionally they are probably either burned and inedible or completely cooked and likely there is no “bishul achar bishul” (repeated cooking).

Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit”a