Knowledge / Selection and temperature ranges
Dry Ice or Frozen Coolant Packs for Pharmaceutical Transport?
Dry ice and PCM frozen coolant packs fulfil different functions. Dry ice may be suitable where very low temperatures are required and permitted for the product. PCM −21 elements may be an option for a bounded range such as −15 to −25 °C. Changing the cooling medium requires a reassessment of the complete packaging.
Practical guidance
Check whether your product requires dry ice or can be shipped with PCM −21, including preparation and possible replenishment.
Foam bricks: depending on the item version, this rectangular format can contain water or PCM.
In this guide
- What is the lowest temperature the goods may reach?
- Dry ice and PCM −21 compared
- What to consider in the packout
- Record the dry ice quantity at packing
- Agree replenishment with everyone involved in advance
- Why a general consumption rate in kilograms per day is insufficient
- Include this information in the enquiry
What is the lowest temperature the goods may reach?
The requirement “frozen” is insufficient for selecting a cooling medium. Check whether a lower temperature limit applies as well as an upper limit. If the goods must not fall below −25 °C, for example, they are not suitable for direct dry ice use merely because they must travel frozen.
Dry ice is solid carbon dioxide. Under usual ambient conditions, it changes directly into gas. The packaging must allow this CO₂ to escape.
Dry ice and PCM −21 compared
| Question | Dry ice | PCM −21 |
|---|---|---|
| Which temperatures may the goods reach? | Use only where very low temperatures are suitable for the product and packout. | May support bounded frozen ranges such as −15 to −25 °C. The melting point does not guarantee the product temperature history. |
| What is needed at the packing site? | Suitable dry ice and the required mass at packing; safe handling and gas release. | Suitable packs and equipment for the preparation specified for the system. |
| How are delays and openings addressed? | Account for mass loss and any planned replenishment in the tested process. | Account for remaining thermal capacity and preparation in the complete configuration. |
| What demonstrates suitability? | Evidence for box, dry ice form and mass, arrangement, payload and transport conditions. | Evidence for box, packs, preparation, arrangement, payload and transport conditions. |
THERMOCON offers PCM −21 as Gelpack Pro, foam bricks and rigid-shell packs.
The −21 °C melting point does not guarantee a particular product temperature history. PCM −21 therefore does not replace a dry ice solution where substantially lower temperatures are required. The pharmaceutical thermal packaging guide identifies information needed to compare quotations.
Source: THERMOCON: PCM frozen coolant packs.
What to consider in the packout
- The product, dry ice and separating components must fit in the prescribed arrangement.
- CO₂ must be able to escape; the packaging must not be sealed gas-tight.
- Duration, ambient temperatures and opening events affect how much dry ice remains on arrival.
- If replenishment is planned in transit, the location, staff, material and procedure must be agreed before dispatch.
The FAA fact sheet describes hazards and packaging requirements for US air transport. For the specific shipment, also clarify the applicable dangerous goods rules and acceptance conditions with the carrier.
For larger shipments, access to and loading of the packaging also matter. The article on pallet shippers for pharmaceutical transport provides guidance.
Record the dry ice quantity at packing
Dry ice absorbs heat as it sublimates and leaves the shipper as gas. It also loses mass during preparation and waiting. The quantity stated by the supplier on delivery therefore does not necessarily equal the quantity inside the shipper when it is closed.
For an initial thermal estimate, the heat supplied can be divided by the usable enthalpy of sublimation. Enthalpy of sublimation describes the heat absorbed per unit mass during the transition to gas. This alone does not create packing instructions: distribution and residual quantity must adequately protect all relevant product positions.
Check the specified dry ice forms and positions, as well as the condition at the latest planned receipt time. If pellets are replaced with blocks, equal initial mass alone is not evidence of equivalence.
Agree replenishment with everyone involved in advance
“Replenish as needed” is insufficient during an extended customs delay. Who has access to the shipment? Is suitable dry ice available? Who may open the packaging, and how long may it remain open? How will the released CO₂ be safely dispersed?
Record the agreed arrangements before dispatch. This planning sheet does not replace the approved work instruction or applicable transport rules.
| To be defined | Arrangement and responsible party |
|---|---|
| Suitable location, access to the shipment and responsible person | __________ |
| Replenishment criterion under the approved procedure | __________ |
| Available dry ice form and required quantity | __________ |
| Permitted opening procedure; product and measurement checks | __________ |
| Record of added mass, time and reclosure | __________ |
| Safe dispersal of released CO₂ | __________ |
The work instruction should define the replenishment criterion, checks on product condition and measurement data, added mass, timing and reclosure. Test this intervention as part of the transport process. For air transport, dangerous goods requirements and carrier conditions must also be agreed.
When considering a switch to PCM −21, first check the goods’ temperature requirements. Only if these can be met is it worthwhile comparing freezing capacity, preparation time, available product space and transport costs.
For biological sample shipments, also establish the requirements for the complete sample packaging.
Why a general consumption rate in kilograms per day is insufficient
A larger shipper, different insulation or additional opening changes dry ice requirements. Use data for the intended configuration and account for planned delays. Dry ice that has sublimated before transport begins is no longer available later.
Document the quantity loaded and the time of packing. The article on qualifying thermal packaging explains how evidence for the complete packaging is established.
Include this information in the enquiry
Specify temperature limits, product dimensions and quantity, initial temperature, shipping duration, transport mode and intermediate stops. Add whether dry ice can be safely sourced and handled on site, or which freezers are available for PCM. This information helps select a suitable cooling medium and matching packout.
Sources
- FAA: Dry Ice Fact Sheet for Shippers & Freight Forwarders. Fact sheet on gas release and requirements in US air transport.
- THERMOCON: PCM frozen coolant packs. THERMOCON formats for PCM −21.
Editorially updated on 5 November 2026.
Check whether PCM −21 suits your shipment
Tell us the upper and, where applicable, lower temperature limit, shipping duration and planned intermediate stops. We can then assess whether PCM −21 is an option for your goods.