Yes, you can use dry ice in an upright freezer, but it's important to follow proper safety guidelines. Dry ice, which is solid carbon dioxide, is extremely cold (-78.5°C or -109.3°F) and can be used to help maintain low temperatures in a freezer for an extended period.
The exact duration that dry ice will keep things frozen in an upright freezer can vary depending on several factors, including the amount of dry ice used, the size and insulation of the freezer, and the ambient temperature. Here are some general guidelines:
Insulation and sealing: Ensure that your freezer has good insulation and a tight seal to minimize the transfer of heat into the freezer. This will help maintain the low temperatures for a longer period.
Amount of dry ice: The more dry ice you use, the longer it will keep the freezer cold. As a general rule, 2.5 to 4.5 kilograms (5 to 10 pounds) of dry ice can keep a standard 18-cubic-foot freezer cold for 24 to 48 hours. Adding more dry ice will extend the duration.
Usage frequency: The frequency of opening and closing the freezer door will affect the duration of the dry ice's effectiveness. Opening the door frequently allows warm air to enter the freezer, increasing the rate at which the dry ice sublimates (converts directly from solid to gas).
Ambient temperature: The temperature of the surrounding environment will impact the rate of dry ice sublimation. If the ambient temperature is very high, such as in a hot room, the dry ice will sublimate more quickly.
It's essential to handle dry ice with caution. Always wear protective gloves when handling dry ice and ensure proper ventilation in the area where the freezer is located, as the sublimation of dry ice releases carbon dioxide gas, which can displace oxygen in poorly ventilated spaces.
Remember that dry ice will eventually sublimate completely, turning into gas without any liquid water. As it does not melt into water like regular ice, there won't be a defrosting phase. Therefore, once the dry ice has sublimated, the freezer will return to its normal temperature, and you will need to rely on the freezer's regular cooling mechanisms to keep things frozen.
It's recommended to consult the manufacturer's guidelines for your specific freezer model and consider using a freezer thermometer to monitor the temperature and determine when additional dry ice or other cooling measures may be needed.