Laboratory Freezer Selection and Organization Guide

Although a seemingly easy decision, choosing the right cold storage equipment is critical for protecting your valuable samples and reagents. Improperly stored samples can cost weeks, if not months, of lost work and thousands of dollars. To this end, it is worth taking a closer look at your options when choosing the right kind of freezer for your valuable research samples. Below we discuss what to consider when buying a low and ultra-low temperature (ULT) freezer.

Cold Storage Equipment Selection

There are several factors to keep in mind when selecting a freezer. The right balance is to identify the need of your lab (long-term or short-term storage and frequency of access) with different storage solutions (storage capacity and footprint) and budget. Here are the general steps to choosing the right freezer for your laboratory.

First, select the freezer type th best meet your laboratory need:

• General purpose: -20⁰C to -30⁰C (ideal for storing enzymes and biochemical)
• Low Temperature: -30⁰C to -45⁰C (well suited for storing biological samples, vaccines, and blood products)
• Ultra-Low Temperature: -45⁰C to -86⁰C (for storing drugs, viruses, bacteria, cell preparations, tissue samples, and long-term storage).
• Flammable Materials and Explosion-Proof: specially designed to store flammable and volatile materials and protect lab workers.
• Plasma Freezer: specifically designed for storing plasma and blood products. These freezers typically have a preset temperature (usually in the -30⁰C range) and meet FDA, AABB, ANRC standards.

Second, select the orientation of the freezer:

• Upright Freezers are ideal for storing large amount of regularly accessed materials. Multiple shelves and rack configuration are a great way to organize your freezer space.
• r-Counter Freezers are great for storing smaller amounts of materials and conveniently located near your workspace for items that require regular access or require constant freezing. These units range in volume from 1 cu.ft. to 7 cu.ft.
• Chest Freezers are ideal for long-term storage and provide greater efficiency and quicker recovery after opening. However, samples may not be easily accessible and they have larger footprint for a given volume of storage. These units are available in a variety of sizes (0.5-20+ cu.ft.)
• Benchtop Freezers are best for storing frequently used samples and reagents, those items you wish to have close at hand, or temporarily storing samples as they are being collected.

Third, consider the size / capacity of the unit:

• Small Capacity (0.5-10 cu.ft.) – small quantity of materials that needs to be kept isolated or need to have close at hand
• Standard Capacity (10-20 cu.ft.) – regularly used materials with configurable drawers and rack system
• Large Capacity (>20 cu.ft.) – ideally suited for large amount of storage or long-term preservation of samples.

Ultra-Low Freezer Consideration

Aside from choosing the right type and capacity, here are some other factors to keep in mind when selecting an ultra-low freezer.

Performance and Control System

• Refrigeration system is how it cools down (cascade refrigeration vs dual independent compressors). Cascade refrigeration relies on two stage cascading process to reach target temperature. The first compressor lowers the temperature to an intermediate temperature and the second compressor takes it down to the final set-point temperature. The drawback of the cascade system is that if one compressor fails, the other will not be able to keep up and the unit will eventually warm up to room temperature (as was the case for a Harvard University lab that lost a priceless collection of human brains in 2012 when one of the compressors failed). An alternate to this system is the dual-compressor system which utilizes two auto cascading compressors simultaneously. This way, if one compressor fails, the other compressor can maintain cryogenic temperature as repairs are being made. This system has been optimized in the Z-SCI Biomedical brand in which it only require one compressor to maintain the temperature at -86⁰C.
• Noise and heat generation opt for 110V or 120V models over 220V to save money and reduce noise. Another way of reducing noise level in working area is to locate all freezers within a common equipment area away from workspace or opt for liquid nitrogen freezer system.
• How many compartments or shelves does the ULT or other cold storage unit have? Better temperature control and uniformity is achieved when the freezer is full as less energy is needed to cool.

Temperature Stability and Recovery

• How fast does the unit recover after door opening to prevent samples from thawing?
• Consider how your samples are stored or organized in the freezer as routine opening and closure of the freezer or keeping the door open for an extended period of time to locate a sample can lead to temperature fluctuations and the risk of exposing your valuable samples to freeze/thaw cycles. Opt for using removable inventory racks to help locate samples easily and prevent keeping the freezer door open for extended periods of time.

Safety and Security

• Monitor/log freezer temperature (visual display of temperature).
• Alarms/monitoring system to notify users of any deviation from the set-points temperature (temperature, power failure, battery life, sensor failure, fan motor failure, and door ajar).
• Power-outage readiness –what happens to your samples if the power goes out or electrical surges occur? Back-up power system should be in place.

Environmental Footprint and Energy Efficiency

• Save money with energy efficient equipment. Newer models have made many improvements in this regard via improvement in compressor technologies, insulation, interior organization, vacuum insulation and frost-free door gaskets.

Maintenance and Warranty / Service Options

To preserve your irreplaceable samples and extend the life of your laboratory freezers, which are significant investments by themselves, consider the following points:

• How much space is required between and around freezers? Leave adequate “breathing space” space between the freezer and the wall or point away from walls. This will improve heat dissipation and lower the chances of component failure due to overheating.
• Consider the ambient temperature of the equipment room. Higher ambient temperatures will lead to compressor overheating and shorten the service life of the unit.
• Do you change or clean the air filter periodically?
• Prevent snow build up around the door as this will result in ice buildup which can prevent door closure and damage the door gasket.

Simple, routine maintenance, defrost, and cleaning to extend the life of your freezer.

General Laboratory and Freezer Space Scenarios

The second law of thermodynamics can be expressed in several ways and one of those states that the degree of disorder is always increasing in the universe. This is especially the case in a laboratory setting where the following scenarios are routine:

• Laboratory enzymes and reagents are kept in several locations, thus, making it hard to determine if the lab is out of it or it is misplaced.
• Several researchers generate cell lines or plasmids but there are no general lab stocks. It is time consuming to determine where something is located and, when found, if that plasmid or cell line is from the final steps or somewhere in the intermediate stages. Or worse still, the lab personnel that generated it is no longer associated with the lab and it becomes difficult to determine what those tubes are and, if they are hazardous or important, which ones should be kept and which discarded.
• Time course experiments generated a lot of tubes and it becomes time consuming and cumbersome to label them all in detail. After a short period of time, it becomes difficult to determine the source of those tubes labeled 1-20 or A-Z.
• You are in the process of generating a cell line, a plasmid, a clone , or making another product that requires several intermediate stages. This requires a way to keep the intermediate stages organized for easy access.

If the above scenarios are relevant to your laboratory, then investing some time to organize your lab space and fridge/freezer will save you a lot of time and money.

How to Organize Laboratory Freezer and Laboratory Space

• Use this freezer inventory log. Keep track of cell lines, plasmids, reagents, primers, or other experimental samples. This sheet can be kept in a lab inventory folder with a separate tab for additional information (such as plasmid maps or cell line details) with reference to the inventory number on the tracking sheet. Need to make changes to the log, add additional fields, or have a way to sort the log by user, tower, sample type, etc., then use excel to create one, based on our example, specific to your needs. Share your improved version with MIDSCI and your fellow researcher.
• Use an inventory tower to keep your fridge and freezer organized. If your fridge/freezer is overflowing with tubes and boxes, then using an inventory rack will not only help with keeping things organized but also makes for an efficient use of space. A tower can be assigned for a specific use (reagents, enzymes, etc.) or assigned to a specific person in the lab. This way, you can look at the inventory list (above), determine where the reagents you want is located, and then pull out the box from a specific tower. This method also prevent fluctuation of freezer temperature - as you keep the door open while digging through all the tubes and boxes to locate an item, prevent frost buildup, and prevent thawing of valuable samples and reagents. Use our freezer rack configurator to select the specific rack that is perfect for your specific freezer model.
• Use boxes instead of tube racks to store your samples. We often start out keeping samples in tube racks while work is in progress. This rack is then stored in the freezer to be further processed at a later time (run a gel, use for PCR reaction, etc.). Then the unfortunate event take place. In the process of finding something in fridge or freezer, you tip over the tube rack and your samples flies all over the place. Not only do you have to sift through the fridge/freezer to locate your samples but you also have to reorganize those tubes. And what if you can’t find a critical sample? Prevent all of this from taking place and store your tubes in a box and keep track using the inventory sheet above. It will take a few more minutes but it will save you valuable time later when it comes to locating a specific sample.
• Require all lab personnel to inventory their reagents, cell line, plasmids, etc. before leaving the lab. It will save you time later when another lab is requesting that reagent used in a specific publication. You’ll be confident that you have the right reagent used as well locate it in no time.

Laboratory freezers are essential and critical in any biomedical laboratory environment. Invest wisely in a reliable and a durable freezer to ensure your samples stay safe and secure with minimal impact on your research progress. Let us help you find that reliable laboratory freezer, call MIDSCI at 1-800-227-9997 today!