When and how to specify an ultralow-temperature freezer

By Rachel Kohn*
Thursday, 08 October, 2020

When and how to specify an ultralow-temperature freezer

At the time of writing Phase 3 clinical trials are underway for COVID-19 vaccines, some of which call for an ultralow-temperature freezer for storage and transport. Examples described in a September Wall Street Journal article note the unusually cold storage temperatures — as low as -80°C — required. COVID-19 vaccine candidates are one of many applications for ultralow-temperature freezers.

Unlike ‘ordinary’ freezers, ultralow-temperature freezers are not inexpensive. But the investment is important when the job is to protect contents of high value and sometimes for long periods of time. Fortunately, there are a number of ultralow-temperature freezers on the market to ease the selection of a model that best suits your needs.

What is meant by ultralow-temperature freezers?

There are freezers, low-temperature freezers and ultralow-temperature (ULT) freezers on the market. Here are some examples that apply to scientific (not commercial or household) freezers. Note that different manufacturers may define the temperature capabilities of their various models differently.

  • Scientific laboratory and pharmacy freezers can control ranges from -10 to -25°C.
  • Low-temperature freezers, depending on the model and function, can have a minimum of -25, -35 or -40°C, also with a user-controlled range.
  • Ultralow-temperature freezers control temperatures down to -86°C, also with precise temperature control.

But remember...

Colder is not always better

Base your decision on the recommended storage temperature for what you put in your freezer. Our next section provides some examples. Just as with your room or central air conditioner, a colder setting means a higher power consumption. 

Keep in mind as well that when you access the unit you allow ambient-temperature air to enter. We’ll get into that later. 

Typical applications

ULT freezers find wide application for biological and biotech storage applications in:

  • most recently — potential COVID-19 vaccine storage
  • research universities
  • medical centres and hospitals
  • blood banks
  • forensic labs for long-term evidence storage
  • establishing performance specs for parts used in extreme environments

In addition to COVID-19 vaccine candidates, other examples require ULT freezers to store biological samples such as DNA/RNA, plant samples and insect artefacts, autopsy materials, blood, plasma and tissues, chemicals, drugs and antibiotics. 

Manufacturing firms and performance testing labs use ULT freezers to determine the ability of products and machinery to perform reliably under severe low-temperature conditions such as found in Arctic and Antarctic regions.

These myriad applications suggest that ULT freezers may house multiple and different experiments, some of which may require frequent checking while others remain undisturbed for lengthy periods of time.

And in fact if they do, this becomes a feature that can be applied to your selection process.

What to look for in a ULT freezer

1. Temperature control

As suggested above, the lower you set the thermostat on a ULT freezer (or any freezer for that matter) the more energy it consumes to maintain that temperature. So again, it is a smart idea to match the temperature capability to storage or environmental testing recommendations. The key is a precisely adjustable thermostat.

For example, Nor-Lake Ultra-Low upright and chest freezers offered by Tovatech allow temperatures to be adjusted and displayed in 0.1°C increments while onboard systems and maintenance diagnostics ensure optimal freezer performance.

You’ll decide how important such a degree (no pun intended) of temperature control is to your requirements. But we suggest you look for models that display your set and actual internal temperature. This can alert you to a potential malfunction in the unit.

2. Temperature excursion alarming

High-efficiency insulation plus cabinet- and door-mounted gaskets contribute to energy-efficient performance. But things can go wrong, in which case an alarming system should provide an immediate alert, and it should be functional in a power outage.

Look for a battery-operated system with an audio and visual alert (and optional remote alerts) that activate if the temperature increases above the set value. Personnel should be able to test the alarm system. A low-battery indicator is a useful feature.

3. Record keeping

Accurate record keeping when storing valuable and/or temperature-sensitive products is critical. It is one of the key requirements, for example, in the CDC’s 2020 Vaccine Storage and Handling Toolkit.

4. Isolating specimens

\When you open a freezer door, you provide access for ambient temperature air. This makes it advisable to select a ULT freezer with separate internal compartments.

Equipment available from Tovatech, for example, has not only a main door but also interior compartments with individual insulated magnetic catch doors. This confines the intrusion of ambient air to the accessed compartment.

Compartments can be fitted with optional individual specimen racks to hold separate containers that in turn can accommodate cell dividers. Labelling compartment doors, specimen racks and individual containers speeds content removal and return, further enhancing operating efficiency.

Selecting your ULT freezer size

How much storage capacity do you really need? All freezers operate more efficiently when they are full. This is because the contents help stabilise holding temperatures.

The criteria for size should also take into account space available (ie, footprint). In brief, interior volumes can range from 370 to 850 L for upright models and 56 to 765 L for chest models.

Other considerations

The Nor-Lake Scientific Select ULT freezer design was beta-tested in a large clinical lab where scientists and technicians commented on several noteworthy features. If your organisation is considering a ULT freezer you’ll probably be comparing the offerings of several manufacturers, and may be interested in what the beta test revealed:

  • Sturdy construction — specifically, door handles/latches that will stand up to years of rugged use.
  • Fast temperature recovery after door opening, reducing incidents of triggering the alarm during daily use.
  • A front-mounted eye-level control system that displays a real-time clock, event logging, alarm history, advanced alarms, alarm test and memory functions.
  • An interior design that readily accepts rack systems and storage containers from other models.

These and other features are among the reasons why this lab decided to move everyday samples to the Nor-Lake ULT freezer design, using their older units for non-routine sample storage.

Other useful features include:

  • Onboard system and maintenance diagnostics to reduce guesswork.
  • Multibulb gaskets on doors and cabinets for temperature stability.
  • Separate internal storage compartments with insulated doors and internal adjustable shelving to minimise content exposure to ambient air.
  • CFC-free foam insulation that contributes to structural strength, as opposed to vacuum panels that can leak and can suffer damage during transport and/or repositioning.
  • High ratio of internal space to external dimensions.
  • Useful options including temperature chart recorders, phone dialers, LN2 and CO2 backup.

To wrap things up

An ultralow-temperature scientific freezer represents a substantial investment. Arm yourself with facts about your particular application, then contact the freezer professionals at Tovatech for advice on selecting a ULT freezer that best meets your requirements.

*Before co-founding Tovatech, Rachel Kohn worked in business development and project management at Smiths Detection, Photon-X, Cardinal Health and Hoechst Celanese. Before that he spent 12 years as an R&D chemist at Hoechst Celanese and Aventis working on advanced drug delivery systems, polymer films and membranes, optical disks and polysaccharides. Tovatech is a leading supplier of ultrasonic cleaners and other lab or small business equipment.

This article has been republished with permission from https://www.tovatech.com/blog/.

Image credit: ©stock.adobe.com/au/paul_burns

Originally published here.

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