Selecting Scientific Refrigeration Equipment
Scientific refrigeration equipment includes refrigerators and freezers used to store vaccines, pharmaceuticals, biological samples and similar temperature-sensitive products and specimens for healthcare, R&D and related applications. Scientific refrigerators and freezers have critical performance requirements generally unmet by residential and commercial refrigeration systems. For this reason they are highly recommended to protect contents that lose potency or are otherwise compromised by what are called temperature excursions above or below recommended storage settings. Therefore, selecting scientific refrigeration equipment for your needs is key.
Correct storage temperatures are usually recommended by professional or government organizations. The CDC, for example, recommends in its 2016 Vaccine Storage and Handling Toolkit that frozen vaccines be stored between -50⁰ and -15⁰C (-58⁰ and + 5⁰F); refrigerated vaccines should be stored at 2⁰ and 8⁰C (36⁰ and 46⁰ F). Vaccine manufacturers indicate correct storage temperatures that should apply along what is called the “cold chain” extending from the manufacturer through transport to the administering facility such as local clinics.
Low-temperature freezers are available for long-term biostorage and biobanking requirements. These units operate at temperature ranges of – 25⁰, -30⁰ and -40⁰C. Ultra-low temperature freezers can be set from -50⁰ to -86⁰C. Cryogenic storage units are also available but are not discussed in this post.
Costs of Improper Storage
Improper storage, malfunctioning equipment, human error and power failures annually cause thousands of dollars in losses due to compromised vaccines.* Costs include vaccine replacement along with the inconvenience of locating and revaccinating people who received compromised vaccine.
Tissues, forensic samples and other biological specimens in long-term storage may be irreplaceable if equipment or procedures fail.
Storage equipment specification and clearly understood standard operating procedures in healthcare and research organizations are first lines of defense to protecting temperature-sensitive pharmaceuticals and biological samples.
Keep these points in mind when purchasing scientific refrigerators and freezers. This post provides guidelines to help you select the correct equipment and offers suggestions on operating procedures aimed at protecting valuable and sometimes irreplaceable contents.
Criteria for Selecting Scientific Refrigeration Equipment
Purpose-built refrigeration equipment is preferred because it is designed to maintain tight temperature control as well as providing other safeguards. CDC’s 2016 Toolkit provides alternatives if purpose-built refrigeration is unavailable.
Here we provide suggestions on what to look for when purchasing a scientific refrigerator or scientific freezer. These recommendations are in no particular order; all have importance when it comes to safeguarding their contents.
Storage Capacity
Selecting scientific refrigeration equipment based on storage size. Refrigerators and freezers are available in sizes ranging from countertop and undercounter units to multiple-door units. Specify the size you need. And what is that? If you have a moving inventory typical of healthcare facilities keep your stock current in accordance with needs and expiration dates.
Using vaccines as an example, select refrigeration equipment with room to store, without crowding, the largest inventory you might have at busiest point in the year – such as during the flu season.
Full refrigerators and freezers (without crowding) do a better job of maintaining temperature. Replace removed stock with cold water bottles or freezer packs. Food and beverage containers are not substitutes for water bottles and freezer packs.
Allow 2 to 3 inches between the contents and the side and back walls of the unit.
If you are choosing a new refrigerator or freezer select one without on-door storage to reduce the impact of ambient temperatures when the unit is open. If you have a unit with door shelves stock shelves with water bottles or freezer packs.
Selecting Scientific Refrigeration Equipment Defrosting Options
Many manufacturers offer automatic defrost, frost free and manual defrost options in their product lines. What is the difference?
Defrosting cycles remove ice buildup on coils and in freezers also remove ice buildup on walls.
Auto-defrost refrigerators have fans to move chilled air throughout the unit in order to create and maintain uniform internal temperatures. During the defrost cycle compressors turn off but the fans continue to run to remove frost accumulation from the coils. The timing of auto-defrost cycles may be inconvenient so some models allow personnel to control the frequency and duration of the cycle.
Manual defrost freezers are better able to maintain temperature uniformity than auto-defrost models. A thin layer of frost accumulating on the inside of freezers does not affect cooling performance, but a thick layer will affect a unit’s ability to efficiently maintain temperatures and will eventually cause failure. Therefore regular defrosting is recommended to help the freezer maintain temperature stability. As a caution, you must have a backup freezer pre-set at the correct temperature for temporary sample storage while defrosting the primary unit.
As well, be certain that the primary unit has returned to the correct temperature before restocking it. The unit’s operating manual should provide recommendations on the time required to reach the desired temperature.
A Note on Low Temperature Freezers
Low temperature and ultra-low temperature upright and chest freezers are generally selected for long-term storage. Many units offer internal compartmentalization equipped with separate access doors that reduce contents to the intrusion of ambient air when scientists place or retrieve samples. Internal sample and specimen storage options include specimen racks and compartmentalized fiberboard containers to reduce time needed to remove and return contents.
Temperature Control and Display Systems
For storage applications where a certain degree of latitude is permitted for proper storage temperature less precise control may be acceptable. Examples are dial-type thermostats with letters or number ranging from cold, colder, coldest.
For tighter temperature control, the more precise programmable logic control is offered and is a recommended choice for maintaining minimum temperature drift. As examples, Norlake Select Scientific Premier refrigerators available from Tovatech are equipped with digital LED display microprocessor temperature controllers with an adjustable range of 2 to 10⁰C and are factory pre-set at 4⁰C. High-end units such as the Select Ultra-Low freezers allow setting temperatures to and display to 0.1⁰C.
Internal temperatures should reflect the temperature of the contents as opposed to the temperature of internal air, which can change quickly when doors are opened. This is accomplished by product temperature sensors which are typically inserted in a bottle of glycerin or glycol to reflect content temperatures. Since the content temperature is the important factor, the product sensors avoid unnecessary temperature alarms set off by routine door openings. Sensors may also be used to record internal air temperature.
Selecting Scientific Refrigeration Equipment Alarming and Recording Systems
Temperature alarming is an absolutely critical feature when storing valuable vaccines, pharmaceuticals and biological specimens. Alarming systems are standard on many of scientific freezers and refrigerators. An example is built-in digital audio and visual high/low temperature alarms, some with remote alarm contacts that can be connected to alert personnel elsewhere in the facility.
If your refrigeration equipment does not have built-in alarming systems it can be fitted with optional digital temperature alarms. These consist of internal sensors placed in bottles as described above. They are connected by wire passing over the hinge-side door gasket or through optional sensor access ports to an external control and display module.
Temperature recording is a very important SOP component for storage of temperature-sensitive products. Record keeping is simplified thanks to the ability of temperature sensors to collect data within the units for validation purposes. Procedures for monitoring and accessing data vary based on the system. Some examples:
- Calibrated temperature monitoring devices with a Certificate of Traceability and Calibration Testing (also known as Report of Calibration)
- A USB device to collect temperature data for quick transfer to a computer
- Calibrated digital data loggers
- Web-based record-keeping systems
Note that while these systems are extremely important lab personnel should manually record temperatures at the beginning and end of the day.
Have a “Plan B” for Valuable Product Refrigeration Storage
As noted above and in the reference below substantial losses are incurred when scientific refrigeration systems fail due to equipment malfunction or in the event of a power system failure. On-site backup generators are an important component of proper storage practices. Generators should be checked on a regular basis to ensure availability if and when the need arises. If your facility is not equipped with backup power or an alternate on-site capability for protecting samples you should establish a plan to quickly relocate the samples to an alternate storage facility.
Please contact Tovatech’s refrigeration specialists for additional information on selecting scientific refrigeration equipment to meet your scientific refrigeration needs.
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*Vaccines for Children Program: Vulnerabilities in Vaccine Management
