First, do not open the freezer door. A freezer full of food will usually keep about two days if the door is kept shut. It should last about a day if it is half-full. If the freezer is not full, group packages together they will retain the cold more effectively. You can also pack your freezer with dry ice, block ice, or bags of ice in the freezer.
Use an appliance thermometer to monitor the temperature of the freezer. Food that retained a temperature of (40 °F), it is safe to refreeze or use. The food may also still be safe to use if ice crystals remain in the food.
Discard foods that have been warmer than 40 °F for more than 2 hours.