In the biological sciences, keeping samples at constant temperatures is a necessity and challenge. Temperature fluctuations that would be acceptable in a home freezer can ruin some types of samples, spoiling work and costing money. The pursuit of suitable refrigeration is one of the major costs for any lab, contributing more to the power bill than all other power expenditures combined. For business reasons and as a service to the environment, biological facilities are always trying to get better refrigeration for less power.
Regardless of the type of refrigeration unit purchased, it will come in either a stand-up or chest model. It is usually easier to organize and find things in a stand-up model because things are convenient shelves. In a chest model, things are stacked on top of each other, and retrieval may be more difficult.
However, chest models suffer less temperature fluctuation when opened because the heavy, cold air stays inside. Every time a stand-up unit opens, cold air pours out and the unit must take time and power to reach optimal temperature again when it is closed.
Because of these factors, it may be best to get a stand-up unit for things that must be used often. Items that will be stored for longer times are better stored in a chest unit.
Some units have internal compartments with their own doors, allowing retrieval of one item without lowering the temperature of all the others.
For storing most research material, reagents or pharmaceuticals, a refrigerator is required to keep the temperature at about four degrees C. If the refrigerator is needed for a function other than storage, it may be necessary to get a smaller unit to fit the available area. For purposes such as chromatography, shoppers should make sure the temperature controls provide sufficient precision.
For colder temperatures, a freezer is needed. These fall into routine use, low-temperature and ultra-low temperature models.
Routine use or everyday freezers are used to store items such as enzymes, chemicals or experimental samples at temperatures around -20 to -30 degrees C. Freezers generally come with a set temperature but are capable of adjustment by about ten degrees up or down. Small models that fit under a workbench can save steps.
Low-temperature freezers with a range of about -30 to -45 degrees C. are used to store blood, tissue and other medical samples. With these and the ultra-low models, temperature fluctuation may be more of an issue, so stand-up models should definitely have sealed compartments or containers.
Ultra-low freezers operate in the -45 to -86 degree range. This type contains items requiring precise temperature control, so shoppers should check the controls before purchasing to make sure they are suitable.
There are also specialized units such as explosion-proof refrigerators for use with flammable chemicals. Alarms can warn of unacceptable fluctuations, and some units have a temperature recording function.
Auberta Zimbel has worked as a marine biologist for the past 5 years and is an avid hiker and adventurer. For more information on using a biorepository visit pbmmi.com.