One way to clean oven racks is to use commercial cleansers and spray them on the racks. There are several methods to get this done.
Commercial cleansers often produce fumes that can be dangerous, so it is best to remove the oven racks from the oven and clean them outside in a well-ventilated area. Place the racks on some newspaper, and apply the cleanser while wearing gloves. Let the racks sit for a period of 10 to 20 minutes before rinsing.
An alternative way to clean oven racks is to place them in a tub of hot water. Add dishwashing soap, vinegar or baking soda to the water, and allow the racks to sit overnight before rinsing.