Dry ice has long been the standard for maintaining cold temperatures during storage or transportation. Many labs use it to pack vials for a courier run or to set up tubes for processing. But is this long-standing method as reliable as many scientists believe it to be? Growing evidence suggests that this traditional tool may be actively damaging samples and jeopardizing invaluable research.
How Dry Ice Is Damaging Samples
The primary issue with dry ice is its physical nature — it does not melt but sublimates, directly converting from a solid to a gas, specifically carbon dioxide. This gas flow is not gentle. As dry ice sublimates, it drives a constant stream of relatively warm gas over any exposed containers. This convection can be up to 100° Celsius warmer than the sample’s temperature, which drives rapid heat transfer into vials and tubes.
Such bursts of warming can trigger micro-thaw events around caps, threads and thin spots in cryovials. Tiny layers can partially soften, then refreeze when gas flow slows down. Over time, repeated cycles create conditions that form larger ice crystals and structural stress, causing cells to rupture when refrozen. The mechanism differs between food and cells, yet the physics of ice growth and thermal fluctuation are the same.
Ice formation and reformation can also strain membranes and internal structures. The University of Minnesota’s BioCoR notes that larger ice crystals are more damaging than small ones. Freezing processes that allow warming can cross thresholds where intracellular ice and membrane injury increase. These are invisible losses that surface as lower post-thaw viability and function.
Why -78.5° Celsius Is Not Cold Enough
Even if dry ice could provide a uniform temperature, its threshold of -78.5° Celsius is insufficient for many sensitive biological materials, raising the risk of damaging samples in any exposure or delay. Research highlights a key concept — the glass transition phase of water, which occurs at around -137° Celsius. Below this temperature, all biological activity effectively stops.
Cell-based therapeutics and other cryogenic materials carry even less margin. Warming a cryovial from -150° to the -80° Celsius range can reignite biochemical activity, then refreeze it minutes later. Each swing is another potential for damage.
Modern Preservation Methods Beyond Dry Ice
Liquid nitrogen (LN2) has long provided a reliable floor for temperature control. LN2 boils at -195.8° Celsius at one atmosphere, which keeps materials far below the glass transition line when stored or moved within a cryogenic workflow.
For transport, LN2 vapor shippers deliver cryogenic temperatures without free liquid. The sample rides in a dry, vapor phase held within an absorbent matrix. This prevents splash risk and reduces contamination while maintaining conditions for long routes. Dry shippers are exempt from hazardous material rules when correctly prepared, as they can retain vapor temperatures while preventing liquid release.
How Automation Helps Keep Samples Safe
Protecting samples extends beyond transport. It also applies to long-term storage in repositories and biobanks. This is where automation holds value.
Manual freezers are a common problem. When a researcher retrieves one sample, they often expose the whole rack or box to warmer, ambient air, causing temperature spikes for all other samples.
Automated systems can solve this by using robots to handle sample retrieval with pinpoint accuracy, allowing access only to the target sample. This maintains the rest of the collection in a stable cryogenic condition, which is crucial for sample integrity. Robot use also helps protect worker safety, as working in extreme cold for long periods can be dangerous.
Cold stress guidance from OSHA and NIOSH outlines the risks associated with extended exposure to low temperatures, even when those temperatures are above cryogenic limits. Moving high-frequency retrieval into an automated method helps meet duty-of-care obligations without slowing science.
Building a Future-Proof Cold Storage Strategy
It is time to reevaluate long-standing cold storage practices, as outdated habits may be hindering new discoveries. Biological samples are the result of years of study and significant financial investment, so they should be protected at all costs.
A resilient strategy starts with honest triaging — which collections must remain cryogenic 24/7, which pathways still rely on dry ice and where the bottlenecks are. Investing in modern technology is a major part of this strategy. This may require switching to LN2 vapor shippers for transportation. It may also mean planning for fully automated processes.
Overall, this is not just about adopting new gadgets or boosting efficiency. It is a fundamental shift toward safeguarding priceless research data to ensure future scientific success. The outcome is a lab designed to prevent sample damage.
Safeguarding Valuable Assets
Biological samples represent years of work and potential breakthroughs. However, the dry ice used to store them creates an illusion of safety — its constant sublimation and insufficient temperature can make the samples unstable over time. Liquid nitrogen and automated storage are two modern options that offer far greater security. It is time to update the default to protect what matters most.
