Caitlin Smith has a B.A. in biology from Reed College, a Ph.D. in neuroscience from Yale University, and completed postdoctoral work at the Vollum Institute.
Maybe you are interested in creating a greener lab and just realized that your old refrigerator palls in the energy-efficiency department. Or maybe you’ve noticed some wider-than-acceptable temperature fluctuations in your lab freezer. Either of these could indicate that your cold-storage systems are due for an upgrade. Cold storage for labs typically includes refrigerators, general-purpose freezers and ultra-low temperature freezers. In all cases, it is crucial for the device to function reliably, because it is safeguarding scientific samples that may be irreplaceable. What should you consider when looking for a new refrigerator or freezer?
Refrigerators
Type of unit
Most lab refrigerators hold the temperature at about 4ºC. Lab refrigerators range from larger models that look like those found in homes, to smaller, more energy-efficient models that fit underneath a counter or benchtop to save space.
Uses
Most lab refrigerators are commonly used for storing research samples and reagents, blood samples and pharmaceuticals. Sometimes refrigerators are used in experiments (such as in chromatography) rather than for storage, in which case you need to determine whether your apparatus will fit within the available space, and whether the temperature controls are suitable for your experiment.
Freezers
Routine-use freezers
Everyday freezers usually hold temperatures between -20°C and -30°C. These may hold enzymes, chemicals or experimental samples. The larger, free-standing freezers are tall, upright units. If space constraints are an issue, smaller models that fit underneath a lab bench are a convenient option (this also lets you put the freezer right at your workbench). Often the freezer will come with a set temperature but allow you to adjust it up to about 10°C in either direction. Upright freezers in all temperature ranges may include multiple inner doors to different compartments, so temperatures of other samples are less affected when you open the door for something else.
Lower-temperature freezers
At about -30°C to -45°C, these types of freezers are colder than the everyday variety described above. These are suitable for blood, tissues and other biological samples. These also come in two forms: the tall, upright models and the shorter chest-type models (like a “deep freeze” used at home). There are situations in which you might prefer one or the other. The upright models are good for storing items that you access regularly, and their vertical features allow for better organization. The chest models are good for longer-term storage (as sample retrieval may require slightly more time and effort) and also for storing larger items that won’t fit in an upright model.
Ultra-low temperature freezers
These freezers usually run at about -45°C to -86°C. These also come in the two models described above (upright and chest) and have the same advantages and disadvantages. An additional consideration, for both low and ultra-low temperature freezers, is that when you open the door of an upright freezer, cold air spills out and is lost faster than with a chest freezer. This is simply because of their construction—cold air settles into the chest and is less inclined to move up and over the chest walls.
Special considerations
Some specialized types of cold storage bear mentioning. Researchers who work with dangerously flammable reagents may need refrigerators and freezers constructed to be safe around flammable or volatile materials. These models, also known as “explosion-proof” units, are built with hermetically sealed compressors and parts free from CFCs,and they are designed to be safe in case of sparks.
Not all types of refrigerators or freezers include, or even require, advanced features. But if you want or need them, you can find models with programmable thermostats and alarm systems that will sound an alert (and send an alarm email) to lab personnel in the case of power failures, warming beyond a user-specified temperature or a door left open. Some also offer temperature logging and recording to ensure sample safety (such as for storing vaccines).
Today’s models are more energy-efficient than their predecessors. But even if your old freezer has some life left in it, you can start going “greener” by doing some easy tasks: defrost regularly (if not auto-defrost); if auto-defrost, operate the freezer full (add bottles of water as needed) to minimize temperature spikes that occur during the coil-heating, auto-defrost functions; clean out old samples, then try to operate using a full or nearly full unit (sharing with another lab can help to cut costs); and use the warmest setting that you safely can use to reduce unnecessary energy consumption.
Conclusion
Most refrigerators and freezers come with some type of adjustable or built-in racks or shelves. But each lab has its own way of storing samples, so many manufacturers also sell accessories to customize your cold-storage space. Not only is this solution neater and more organized, which keeps work running more smoothly, it’s also more energy-efficient. Smarter internal storage arrangements mean fewer refrigerators or freezers are necessary. Also, when you can quickly find what you need and then shut the door, you don’t waste energy letting the cold air out (not to mention letting everyone else’s samples warm up). New models of fridges and freezers (plus accessories!) can help your lab be greener and more organized—a great combination.