Laboratory refrigerators are used to cool samples or specimens for preservation. They include refrigeration units for storing blood plasma and other blood products, as well as vaccines and other medical or pharmaceutical supplies. They differ from standard refrigerators used in homes or restaurant because they need to be totally hygienic and completely reliable.
Laboratory refrigerators need to maintain a consistent temperature in order to minimize the risk of bacterial contamination and explosions of volatile materials. To achieve a high degree of accuracy the refrigerator needs air to circulate and a fan to maintain an even temperature at all times. The fan turns off when the door is open to prevent cold air from blowing out of the unit. Laboratory refrigerators feature separate compartments to prevent cross contamination and can hold specific medical supplies, such as blood or vaccines.
There are four types of laboratory refrigerators.
Explosion proof refrigerators are designed to store flammable liquids and hazardous chemical substances. A lack of electrical equipment prevents fire caused by sparks in the storage area, making it safe to use with combustible materials.
Lab fridges are designed to maintain consistent temperatures and monitor the temperatures with digital displays. They are general laboratory refrigerators and need to include lockable easy-to-clean sections. They are also used to cool samples and for preservation.
Blood bank refrigerators comply with all American and European regulations. Reliability is critical for this type, along with the ability to monitor temperatures. They also need to have separate compartments for storing different sample types.
Chromatography refrigerators are designed for research experiments. They are best used for laboratories where medical samples and procedures require precise temperature settings and stability. For example, a lab refrigerator can be used to set up a chromatography apparatus within the refrigerator chamber. See image to the right for an example.
Laboratory refrigerators typically operate from 2°C to 10°C, although there are exceptions. It is best to use a refrigerator that closely meets temperature needs because the lower the temperature the more power it requires. The control settings for laboratory refrigerators can range from a simple dial thermostat (cold, colder, coldest) to a sophisticated digital LED display that allows for precise programmable logic controls.
Low-humidity laboratory refrigerators minimize moisture in the ambient air. Reduced-humidity laboratory refrigerators are designed for seed storage and applications in which the refrigerator doors are opened and closed frequently. Another helpful feature is an automatic defrost function. This keeps the refrigerator frost-free and running at optimum capacity. In an automatic defrost cycle, the compressor shuts off and the fan blows air over the coils to remove the frost. An internal fan circulates the air throughout the refrigerator keeping the temperature uniform. Laboratory refrigerators with manual defrost systems are recommended when it is important to protect samples from drying out.
For faster pull-down and recovery times, some laboratory refrigerators are equipped with features such as bypass refrigeration and microprocessor-based controls. A rear-wall plenum and heatsink on either the plenum or the floor can help to limit the temperature rise.
When selecting a laboratory refrigerator it is important to consider the space needs. If space is limited in the laboratory then the refrigerator can be mounted on the wall or incorporated into another unit. Some laboratory refrigerators are designed to fit under a laboratory counter. Space-saving designs are more susceptible to temperature fluctuations because of their size. Larger stand-alone units are also available.
Most laboratory refrigerators are equipped with one or more solid doors or sliding glass doors. The refrigerators need to lock in order to prevent unauthorized personnel from accessing dangerous items such as clinical samples, narcotics, and vaccines.
Typically, the adjustable shelves in laboratory refrigerators are made of metals such as aluminum or stainless steel. Products with shelves made of coated wire are also available. By design, most refrigerator shelves are washdown-capable, sanitary, or hygienic. Many refrigerators also have locable drawers or separate cabinets as well as an alarm system. This can help eradicate cross contamination of materials and stop unauthorized personnel handling sensitive items.
Laboratory refrigerators that comply with regulations from agencies such as the U.S. Food and Drug Administration (FDA) are designed to provide specific levels of temperature control and a uniform temperature throughout the chamber. Additional standards include A-A-52150 which defines technical and quality assurance requirements for a non-food, explosion proof, laboratory refrigerator and BS 4376-1 for electrically operated blood storage.