Dry ice for vaccine transportation

Dry ice ( $\text{CO}_2$ ) is an absolutely indispensable solution for maintaining the cold chain when transporting temperature-sensitive cargo, particularly vaccines such as mRNA vaccines, which require storage at extremely low temperatures (often down to $-70^\circ\text{C}$ and below). Its unique property of sublimation—the direct transition from solid to gas at $-78.5^\circ\text{C}$ —makes it the gold standard in medical logistics. This ensures that sensitive biological materials remain in a perfect state of deep freeze throughout the entire journey without coming into contact with meltwater, a critical factor for preserving the efficacy and sterility of the vaccines. The use of dry ice prevents the risk of thawing and spoilage. Thus, dry ice provides the reliability necessary for the global distribution of vaccines and is a key element in combating pandemics. Proper application and adherence to international dry ice transport regulations ( $\text{UN 1845}$ ) ensure the safety and integrity of this vital cargo. Without dry ice, delivering vaccines over long distances would be virtually impossible.

Mechanism and physical advantages

At a sublimation temperature of $-78.5^\circ\text{C}$ , dry ice creates a thermal buffer that is ideal for ultra-cold conditions. When dry ice pellets or blocks are placed inside a specialized thermal container, they gradually evaporate, displacing oxygen and creating a protective $\text{CO}_2$ environment. This also slows down bacterial growth and oxidation, although the primary function is cooling. The immense cooling capacity of dry ice per unit of mass allows for a reduction in the overall volume and weight of the cargo compared to other refrigerants, which is critically important for air freight.

Logistics requirements and packaging

Vaccine transportation with dry ice requires strict adherence to international standards. Firstly, specialized packaging is necessary: highly insulating thermal boxes (typically made of expanded polystyrene or vacuum-insulated panels). Secondly, the container must never be airtight. This is the most crucial safety rule. The sublimation of 1 kg of dry ice produces approximately 540 litres of gaseous $\text{CO}_2$ . If the gas cannot escape freely, the pressure inside the container can lead to an explosion. Therefore, the packaging must have a ventilation hole. Failure to follow this rule is a serious safety violation.

Quantity calculation and UN 1845 safety

Companies performing vaccine transportation must accurately calculate the required amount of dry ice based on the duration of the journey, the quality of the thermal container, and the external temperature. On average, sublimation occurs at a rate of 1-2 kg per day in high-quality boxes. An insufficient amount of ice can lead to a break in the cold chain and subsequent spoilage of the costly cargo.

Due to the risk of large volumes of $\text{CO}_2$ being generated (which can cause asphyxiation in unventilated spaces, such as an aircraft cargo hold), dry ice is classified as a Class 9 dangerous good with the number UN 1845. This requires:

Marking: The container must be clearly labeled as "DRY ICE, UN 1845, CLASS 9" with the net weight of the ice specified.
Documentation: The presence of a shipper's declaration and accompanying documents confirming compliance with $\text{IATA}$ regulations (for air freight) and $\text{ADR}$ (for ground transport).
Personnel: Drivers and handlers must undergo safety training for working with the cryogenic agent and be familiar with the action plan in case of leakage. Individuals handling the ice must use thermal protective gloves to avoid frostbite.

Dry ice for vaccine transportation is more than just a refrigerant; it is a critical logistical tool that ensures global access to life-saving medical supplies. Its application demands high precision, specialized packaging, and strict adherence to international safety rules. Only through thorough preparation and professional logistics using dry ice can we guarantee the integrity and effectiveness of vaccines at every stage of the journey.