A sample freezer failure is the worst case scenario for many laboratories. Do you have a process in place if your ULT freezer malfunctions?

It’s the worst case scenario for many laboratories and sample storage centres, your freezer has failed and your samples are ruined.

Whether it is due to the failure of a compressor, the power supply, or a temperature control issue, an ultra-low storage freezer failing can mean vital samples are spoiled within a matter of hours. With the sheer amount of user parts and variables in upright freezers it means that when they are employed for long term use, failure is a matter of when, not if.

The effects of sample freezer failure
In September 2019 a freezer failure at a Los Angeles hospital led to the destruction of 56 stem cell samples harvested from child cancer patients. The freezer’s temperature sensor did not detect the failure, so it was not discovered until after the samples were spoiled.

A lawyer for the families affected, Adam Wolf, said: “Typically, stem cells and embryos are frozen specifically due to the concern they will not be available - or will be of inferior quality - if an attempt is made to produce them later. This is a tragedy for the victims.”

A similar but much larger malfunction occurred at the Harvard Brain Tissue Resource Center in 2012 when the world’s largest repository of autistic brain samples suffered a freezer failure. The unit’s temperature alarm failed to sound despite the interior of the freezer being close to that of a domestic refrigerator. It was thought this failure may have set autism research back by a decade.

A variety of vitally important samples are found in facilities throughout the world. They can often be an important part of scientific studies into diseases which have the potential to affect billions worldwide

These events show the devastation caused by the unpredictable failures of upright mechanical freezers. However, with upright freezers still so prominent in labs worldwide due to their ease of access benefits, what is the solution?

Minimising upright freezer failure
There are a few workarounds you can employ to ensure samples are not ruined should the worst happen. One of the most popular is to have one or more empty back-up freezers running at all times so samples can be moved quickly if a freezer fails. But this is costly both environmentally and financially.

Even ULT freezer manufacturers themselves are well aware of the risk of freezer failure. Manufacturers will often employ in-built power back-ups and release official advice on the best ways to avoid total sample loss during failure.

Many freezers will feature temperature alarms to indicate when temperatures become unsafe. But, as the two examples above show, these are often not reliable.

There are several common failure sources for ULT freezers such as:

A malfunction in the compressor. These typically use a refrigerant such as ethane (R170) or propane (R290).
A power outage. Freezers will sometimes feature a back-up power system, but these can be limited and unreliable.
Electronics failure. Temperature is often managed digitally.
HVAC system failure. The design of upright mechanical freezers means there is a huge amount of heat being displaced. If your HVAC system fails, this heat can begin to warm the freezer and spoil samples.
Simply forgetting to shut the door. Though many freezers do have indicator alarms when the door is left open this is still a possibility.
If your freezer malfunctions and samples are no longer safe, they should immediately be moved to a back-up freezer, assuming the fault was detected before samples were spoiled. The failure should then be communicated to the person responsible. Your facility should have its own process in place clearly displayed on or near the freezer itself.

However, even with all these processes and back-ups in place, failure continues to be a price paid for using ULT upright freezers.

The best solution
If compressor faults, power outages, HVAC malfunctions and leaving doors open are the main culprits behind freezer failure, then removing these factors is the best solution.

The MVE Variō™ series variable rate nitrogen vapour freezers offer an alternative to mechanical minus 80°C upright freezers and a solution to all the issues above. Able to run comfortably at an entirely user-defined temperature between -20°C and -150°C, the Variō™ pushes liquid nitrogen through a heat exchange system and utilises the vaporisation energy of liquid nitrogen for precise and stable temperature control.

Thanks to its unique design the Variō™ has no compressor and consumes less than 1% of the power used by upright freezers. The system will continue to protect samples assuming a regular supply of LN2. It also entirely removes the need for an expensive and unreliable HVAC system in your cryo-room.

Unlike typical cryogenic LN2 freezers, samples are not kept in or near liquid nitrogen, significantly reducing the risk of contamination. This also means the temperature can be comfortably maintained for a period even if the lid is left open. Similarly, the level of insulation means it will take four days for the temperature to rise from -80°C to -60°C if the liquid nitrogen supply is stopped.

Overall the Variō™ variable rate sample freezer offers a far more secure and reliable solution to mechanical ULTs. Standard upright freezers may be the industry standard, but it is up to users to decide whether the benefits outweigh the costs.

To find out more visit the Variō™ product page: https://www.airproducts.expert/uk/biomedical/vario-series.php
Call us on 0808 164 8548, or email apukinfo@airproducts.com.