To clean an oven after fumigation, ensure it is thoroughly wiped down inside and out with a damp cloth and a mild detergent. This helps remove any potential residue or odors. If the oven has been exposed to fumigants, clean all removable parts, such as racks and trays, by washing them with warm, soapy water. Run a cleaning cycle if the oven has a self-cleaning feature to ensure it is free of any residual chemicals.