A door gasket is the lining that goes around the doors of your refrigeration equipment to ensure proper air flow. With cold equipment, such as refrigerators, freezers, and walk-ins, the gasket is rubber and lines the entire door to keep cold air in and outside air out. Every 12 months or so, check to see if your refrigerator gaskets are in good condition. One way to tell if a seal is bad is the paper test. Put a piece of paper between the door and the fridge, close the door, and then pull.