The facility should have floors, walls, and ceilings constructed of suitable, approved materials which are durable, smooth, impervious and easily cleaned. Walls should be light colored and well-joined, and floors should be adequately sloped for drainage to trapped outlets. Openings to outside and/or non-food-processing or -handling rooms or facilities must be sealed. Instrument panels should be appropriately locked and sealed to prevent harborage of insects. Windows and doors must be tight and close-fitting. And doors in food-processing areas self-closing.