How laboratory refrigerators and freezers are used in the laboratory
A laboratory refrigerator or laboratory freezers have an obvious and essential function; these units are used to chill or freeze samples for preservation. Refrigerators are typically used to store samples at -5 to 15 degrees Celsius, while freezers will typically store samples at -25 to -15 degrees Celsius.
Some laboratory freezers are used to store biological samples, such as vaccines, at a significantly lower temperature. Cryogenic freezing is also used in some laboratories, but requires specialized equipment that is capable of generating and tolerating exceptionally low temperatures. Ultra-low temperature freezers (typically -50 degrees C and below) typically use a dual-compressor cascade-type system to achieve these low temperatures. The first compressor is used to obtain a temperature of around -40 degrees C, after which the second compressor is activated to achieve the lower temperature that is needed. These lab freezers will generally be noisier than a -20 degree C freezer, generate more heat in the room, and use more energy. They are also more expensive to repair than a standard laboratory refrigerator or freezer if the compressor needs to be replaced, as this will require a repair technician who specializes in these somewhat exotic compressors.
Laboratory refrigerators and freezers include equipment for storing samples and special instrumentation used to perform experiments that require precise temperature control. For example, a laboratory refrigerator can be used to install a chromatography apparatus inside the refrigerator chamber.
Refrigeration and freezing equipment is also used for the storage of medical or pharmaceutical supplies. A blood bank uses a laboratory refrigerator to preserve the quality of its blood supply. Laboratory refrigerators and freezers that store blood and blood products must meet a variety of quality and regulatory standards for obvious reasons. They normally come with an alarm system to warn laboratory staff of equipment failure. Plasma can be stored frozen in a plasma freezer for an extended period of time. Since the typical expiration date is one year from the draw date, the problem of maintaining an adequate blood supply is greatly reduced. Pharmacies can also use a laboratory refrigerator to store vaccines, medications, and other temperature-sensitive compounds.
Laboratory refrigerators and freezers include equipment for freezing blood plasma or other blood products for future use. Some laboratory freezers are used to store enzymes or other biological reagents used for testing. Laboratory refrigerators and freezers can be freestanding upright units or can fit under the laboratory counter. A laboratory freezer may also be equipped with locks to restrict entry and may even be designed to safely isolate flammable materials from electrical sparks. Some laboratory refrigerators and freezers are also used as incubators that alternate between a heating period and a cooling period. These types of refrigerators are often used to culture and monitor the growth of bacteria.
Flammable chemicals that require refrigeration should only be stored in a laboratory refrigerator that is designed for the safe storage of flammable products. A flammable liquid is defined as one that has a flash point of less than 100 degrees F (38 degrees C). Laboratory Flammable Storage Refrigerators are UL approved for the storage of flammable chemicals; Laboratory freezers are also often used for this purpose. Flammable storage refrigerators do not have electrical spark devices, relays, switches, or thermostats that can ignite flammable vapors inside the cabinet. They may also incorporate design features such as thresholds, self-closing doors, magnetic door seals, and special interior cover materials that control or limit damage should a reaction occur within the storage compartment.
A label stating ‘Flammable Materials Refrigerator – Keep Away From Fire’ must identify such refrigerators. Flammable storage units cannot be placed in a room containing explosive vapors, but chemicals that give off explosive vapors can be safely stored inside. They are called laboratory-grade, fire-proof, or explosion-proof refrigerators. These refrigerators are more expensive than standard home or even laboratory refrigerators, but should be used if flammable products are to be stored in the refrigerator.
Explosion Proof Laboratory Refrigerators and Freezers are UL Listed Explosion Proof and are similar in design to flammable storage units, but also have all operating components sealed against the ingress of explosive vapors. Electrical junction boxes are also sealed after connections are made. These units are approved for the storage of volatile materials in areas with explosive atmospheres and are the most expensive of all the types. This type of refrigerator is only required when flammable materials are stored in an area with an explosive atmosphere, such as a solvent distribution room. An explosion-proof laboratory refrigerator has very limited use on campus and requires special wiring for hazardous locations rather than simple plug-and-cord connections.