A common source of moisture in the freezer is the outside air that enters via a worn-off seal. You can check if it’s working properly through the dollar bill test mentioned earlier and replace it if needed. Some other ways to control moisture and frost build-up are: a. Don’t leave the freezer door open for long b. Check the door hinges and tighten them if loose c. Keep the food organized and avoid overfilling d. Keep the freezer at -18°F temperature e. Regularly clean the air vents