Warm and cold spots are a natural occurrence in ultra-low temperature (ULT) freezer systems — one that the manufacturers have acknowledged. Most minus 80-degree freezer manufacturers recognize there is generally a 5- to 10-degree difference between the coldest and warmest areas inside of a freezer system. Without the right practices and procedures in place, this temperature range can widen even further — to detrimental levels.
With this blog post, our goal is to help paint a clearer picture of the causes of freezer temperature variation in ULT lab freezers and how proper maintenance helps to keep freezers operating within their recommended temperature ranges.
Why Temperature Variation Occurs in ULT Lab Freezers
Based on the way fan motors are engineered, they are susceptible to the stress of extreme temperatures, and thus will not work at a temperature of -80℃. This ultimately means cold air cannot be circulated freely inside an ultra low temperature lab freezer by a fan, and so an alternative approach is needed. This is also why it is so important to monitor these temperatures.
To this end, most -80℃ freezers are built with small gaps behind, in the front and on the side of all the shelves. While these narrow openings enable air to circulate within ULT freezers, room temperature air also moves through these spaces into the cold storage appliance when the door is opened, leading to temperature variations. Temperatures at upper shelf levels are likely several degrees warmer than the bottom of the freezer, where the temperature is the coldest. The top of the freezer is generally the warmest since warm air rises. This is why temperature mapping ultra low temperature freezers is important.
When Freezer Temperature Variations Are Wider Than Normal…
Consider this scenario: all of the shelves inside a ULT freezer are filled with racks of lab samples, and frost has built up within the freezer. The combination of these elements can restrict the movement of air through those small gaps around the freezer shelves. With nowhere for the air to go, the temperature range between the warmest and coldest areas of the freezer can be more than 15℃.
Recognizing what this wide temperature variation can mean for the integrity and safety of lab samples, most manufacturers recommend defrosting -80℃ freezers at least once a year. Defrosting a freezer regularly ensures there is room for air to move inside the freezer, while also giving labs the chance to take complete inventory of their freezer and improve its organization.
Some labs operate under regulations that require checking temperatures at various locations in the freezer (aka temperature mapping) on an annual or biennial basis. Mapping will identify areas with the warmest and coldest temperatures in the freezer. Considering the stability of samples under various temperatures for extended periods of time, lab personnel can use these insights to make the optimal decision on where to store temperature-sensitive specimens in the freezer.
Monitoring Lab Samples in Ultra Low Freezers
With a remote temperature monitoring system from CORIS, you’ll get the data you need to analyze temperature fluctuations in ultra-low temperature freezers while receiving real-time alerts to notify you of potential failures. Collectively, our goal is to help you proactively address and respond to lab freezer issues so you can protect the safety and quality of your specimens.
With that in mind, we’ve put together a resource that offers practical tips on how to maximize the lifespan of your lab freezer and minimize the odds of disaster. Download a free copy of the eBook.