Confirming the Safety of Those Administering COVID-19 Vaccines Through Carbon Dioxide Monitoring

August 31, 2021

Carbon dioxide testing for COVID-19 vaccine administrators.

The science behind the vaccines helping to fight the COVID-19 pandemic is impressive, but the vaccines have special requirements for storage and transport that require extra care. The work of Terracon’s industrial hygiene team helps ensure the vaccines are handled properly, while helping to verify safe conditions for those administering the vaccines.

The first two COVID-19 vaccines approved by the Food and Drug Administration for emergency use feature mRNA technology that requires them to be stored at very cold temperatures for extended storage — as cold as -13 degrees Fahrenheit (°F) for the Moderna vaccine and -112 °F for the Pfizer vaccine – far colder than any industrial freezers found at drug stores, doctor offices, vaccination sites, or even most hospitals.

As rollout ramped up, the solution was to package and ship the vaccines in dry ice, which is frozen carbon dioxide (CO2). At -109 °F, dry ice solved the issue, keeping the mRNA vaccines at the proper temperature for short transport periods. However, as dry ice thaws and sublimes back into gaseous carbon dioxide, it presents a hazard for those receiving, storing, and administering the vaccine, especially indoors.

CO2 is a part of the natural atmosphere; humans expel it with every breath. But over-exposure to CO2 can lead to dizziness, headache, nausea, shortness of breath, and other serious health issues. Industrial hygienists in Terracon’s Phoenix office conducted air sampling for CO2 at a local pharmacy storage site to see if the introduction of several pounds of dry ice, with normal building ventilation, would be a hazard to those tasked with storing and distributing COVID-19 vaccines.

Measuring CO2 Levels

The pharmacy site was typical of others around the country in that it didn’t have specially ventilated areas. The ventilation system was a typical heating, ventilating, and air conditioning system installed when the facility was constructed. Terracon’s industrial hygienists measured personal exposure to CO2 during several dry ice/vaccine handling simulations, including transfer of dry ice (and vaccine when in the shipment) from the shipping container to a portable cooler, removing vaccine from the cooler for distribution to a clinic, and supplementing dry ice to the cooler as the amount decreased by sublimation. Several simulations were conducted during the one-day survey. Terracon also measured general pharmacy air concentrations at two locations over a 24-hour period to observe concentration trends and changes caused by the building ventilation system.

The dry ice was weighed when received, and periodic weight measurements were also taken, to determine just how much dry ice sublimated during the 24-hour period. The result: 15.5 pounds in 20 hours in the system tested. As one might expect, the evaporated dry ice did indeed raise the carbon dioxide level in the pharmacy. The good news was that the personal exposure was well below safety thresholds set by the Occupational Safety and Health Administration, and the measured general-area levels did not exceed those comparable to a typical densely occupied building.

Clients rely on Terracon’s nationwide network of industrial hygiene professionals to address a variety of challenges, from asbestos and lead exposure to mold remediation and noise monitoring, just to name a few. The COtesting in this case confirmed that the mRNA COVID-19 vaccines could be administered indoors in typical pharmacy settings with no safety impacts to workers.


Mike Crandall, CIHMike Crandall, CIH, is a senior consultant in the Terracon's Phoenix office. He has more than 40 years of experience in industrial hygiene and building investigations, working with residential, commercial, and institutional clients.  

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