Choice of Freezer - Chest Freezer or Cabinet Freezer?
Is it best to use a cabinet freezer or a chest freezer? A cabinet freezer has an opening in the front and takes up considerably less floor space than a chest freezer. This means that more samples can be stored per square meter than when using chest freezers. Cabinet freezers normally have active cooling surfaces in the three vertical walls, as well as in the ceiling and bottom, but passive insulation in the door. Chest freezers have a top opening and normally active cooling surface in the upper 2/3 of all four sidewalls, and passive insulation in the bottom and lid.
The disadvantage of cabinet freezers is that they are exposed to so-called cold rays at opening. Cold air is heavier than hot air so the air in the freezer will "run out" upon opening and cause a temporary increase in temperature in the freezer. When the cold air runs out, warm, humid air enters the freezer, providing condensation and icing on samples and interiors. This will be unfavorable at high opening and closing frequencies. Newer cabinet freezers do have solutions that minimize cold shifts and temperature fluctuations, but long-term storage of biological material recommends the use of chest freezers.
When storing live cells, it is most common to use nitrogen tanks where the samples are either stored in liquid nitrogen or in the gas phase holding - 196 °C. Nitrogen storage requires regular replacement of nitrogen tanks or the possibility of connection to central nitrogen supply. At Oslo University Hospital (OUS) this is a challenge both in terms of space and nitrogen supply. An alternative is mechanical (compressor-based) cryo freezers which are chest freezers that keep temperature down to - 150 °C. Both nitrogen tanks and mechanical cryo freezers are expensive, with a starting price of about NOK 150,000 excl. VAT.
At OUS, chest freezers in the range of 500-700 liters are the most commonly used for long-term storage of biobanks. If you are going to store your freezer at the Regional Storage Facility ("Myrens verksted") you must choose a chest freezer since they only have chest freezers for backup.
Remember that the racks used in chest freezers and cabinet freezers are different, so it can be advantageous to choose the same format if you already have several freezers, or for example have a backup freezer. Racks are often purchased together with the freezers and constitute a significant share of the cost. There are numerous variants of racks adapted to different cabinets and chest freezers. Consult with the supplier what suits your purpose. The biobank and registry support department can also help you with advice.