Dry ice does not evaporate

dry ice sublimation
Dry ice shown in sublimation

By Matteo Zonta, Chef régional des ventes, Canada, Regional Sales Leader, Canada

Accuracy is critical during vaccine distribution reporting

The one thing that can be said about the SARS CoV-2 pandemic is many of us have been given a crash course in virology, epidemiology, and now physical chemistry. With the first mRNA vaccines getting approved in a growing number of jurisdictions and the Pfizer vaccine needing to be transported at ultralow temperatures using dry ice, there is a thirst by many of us to learn more about these vaccines, the immunization process, and the cool science of dry ice. But, in your quest to learn more, I ask you to keep in mind one word—accuracy.

In my search to learn more, I recently listened to a news segment where a reporter described how the Pfizer vaccines are transported and how dry ice is a crucial component because it maintains a temperature of -78.5°C in its solid state—the same temperature needed to keep the Pfizer vaccine safe. The reporter mentioned that as dry ice warms up, it evaporates back into gaseous carbon dioxide — and this is where physical chemistry and the need for accuracy comes into play.

I cringed. Dry ice does not evaporate, it sublimates. I made a point of trying to correct the reporter by talking to her through my laptop screen as I listened on, hesitantly. This reporter was not on top of her science, and while it was not detrimental, it was unsettling to me because I had the word accuracy at the top of my mind. I knew she was not reporting accurately, even if it was a small blunder.

I remember learning about phase transition in high school as we learned about solids, liquids, and gases, and how something can move from one state to another due to factors such as temperature and pressure. I remember that high school lesson well — solid H2O (ice) melts into liquid H2O (water) which evaporates into gaseous H2O (vapor). Phase transition does not have to move through each state but can go directly from a solid to a gas, and this is called sublimation. The solid form of carbon dioxide sublimates into the gaseous form of carbon dioxide and creates the theatrical fog we have all seen at Halloween.

Perhaps, this reporter just made a mistake that most likely will not hinder the vaccine distribution process, but how many other inaccuracies might occur that could potentially hurt the process of getting billions of people vaccinated as soon as possible?

The need for accuracy is critical

Honest mistakes happen all the time. I can easily forgive anyone who is not as enthusiastic about phase transition as I am. Putting my tongue-in-cheek perspective on evaporation versus sublimation aside, there is a very important need, more than ever, for accuracy. As we embark on the journey to vaccinate billions of people, move to herd immunity, and regain some normalcy post COVID-19, it’s imperative for our success that we strive for accuracy with vaccine information, accuracy with the vaccine cold chain, and accuracy with the vaccine chain of custody.

Maintain an accurate vaccine cold chain

To maintain accuracy in your vaccine cold chain, consider using Traceable® temperature monitoring devices. Traceable products have an individually numbered Traceable Certificate provided with each unit, that assures accuracy from our ISO/IEC 17025:2005(1750.01) calibration laboratory accredited by A2LA.


The challenges that come with distributing COVID-19 vaccines using dry ice will diminish as additional vaccines made available will require the traditional +2 °C to +8 °C vaccine cold chain. However, the need for accuracy will not — accuracy with information, accuracy with vaccine cold chain and accuracy with vaccine chain of custody. Keeping accuracy top of mind can help keep more vaccines safe, immunize more people faster, and hopefully get us back to normalcy in 2021.

See Cole-Parmer’s Vaccine Cold Chain resource page for more information on how we can help you with your vaccine cold chain.


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Learn more about the vaccine cold chain: The Cold Chain Facilitating Vaccine Distribution

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