Next-Gen Cold Chain Packaging: PCM vs Dry Ice
Specialty Cold-Chain
Key takeaways
PCM holds a fixed set point such as +5 °C or -20 °C as it changes phase, while dry ice sublimes at about -78.5 °C and is used for deep-frozen payloads.
PCM can replace dry ice for refrigerated, CRT and -20 °C shipments, and special PCMs now reach -60 °C, but most payloads colder than -60 °C still ship on dry ice or liquid nitrogen.
Dry ice is UN1845, Class 9, for air transport, with marking, venting and carrier arrangements under 49 CFR 173.217 and the IATA rules.
Gel packs suit refrigerated shipping but cannot keep a payload frozen, so overnight frozen shipments usually need dry ice or a frozen PCM.
Reusable PCM lowers per-trip refrigerant cost and waste, but needs conditioning capacity, return logistics and inspection between uses.
PCM vs dry ice is the main refrigerant decision in cold chain packaging. Phase change materials (PCM) hold a precise set point, such as +5 °C or -20 °C, and can be reused. Dry ice holds deep-frozen payloads near -78.5 °C but is consumed on every trip and is a regulated dangerous good for air transport. Gel packs and liquid nitrogen dry shippers fill the gaps on either side.
This guide compares the four refrigerant options, explains when PCM can replace dry ice and when it cannot, and sets out the regulatory, cost and sustainability factors behind the choice. It focuses on the refrigerant. For the box around it, see our guide to temperature controlled shipping containers.
What is the difference between PCM and dry ice for cold chain shipping?
PCM absorbs heat while it melts at a designed temperature, so it holds a payload near that set point, from about +20 °C down to -20 °C and, with special formulations, to about -70 °C. Dry ice is solid carbon dioxide that sublimes directly to gas at about -78.5 °C, so it provides deep-frozen conditions but cannot hold refrigerated or CRT ranges, and it is regulated for air transport.
The practical differences follow from that. PCM must be conditioned, frozen or refrigerated, before use and can be reused many times. Dry ice arrives ready to use, starts losing mass the moment it is packed and must be replaced for every shipment. PCM packs are generally shipped as non-regulated goods, while dry ice brings marking, venting and carrier rules. The comparison table below sets the options side by side.
Understanding next-generation cold chain packaging materials
Cold chain packaging keeps evolving to meet the demands of pharmaceuticals, biologics, cell therapies and clinical trial materials. The refrigerant determines the temperature a shipper holds, how long it holds it, how heavy the package is and which rules apply. Four options cover nearly all healthcare shipments.
What are phase change materials (PCM)?
Phase change materials absorb and release heat at a predefined temperature as they melt or solidify. Because a phase change absorbs a large amount of energy at nearly constant temperature, a PCM pack keeps the payload close to its set point until it has fully changed phase. PCM cold chain systems are engineered for specific ranges: about +5 °C for +2 °C to +8 °C shipments, about +20 °C for CRT, and -20 °C PCM for frozen payloads. For the science in more detail, see our guide to phase change materials in packaging.
PCM cold packs come as gel or wax pouches, rigid bricks, bottles or panels. Eutectic ice packs are a type of PCM made from salt solutions that freeze below 0 °C, which makes them useful for frozen and sub-zero ranges. At the cold end, Kaneka announced in January 2022 a PCM with a melting point of about -70 °C that enables shipping at -60 °C or below without dry ice, and that the company says can be reused.
How does dry ice packaging work?
Dry ice is solid carbon dioxide. It sublimes at about -78.5 °C (-109.3 °F), turning directly into gas and providing ultra-cold conditions for frozen biologics, enzymes, cells, plasma and diagnostic specimens. It is effective and widely available for short shipments that demand deep-freeze temperatures.
The gas it releases is the main hazard. Packaging must vent carbon dioxide so pressure cannot rupture the box, and in aircraft the gas can build up in the cabin or hold. The amount needed depends on box insulation, transit time and ambient conditions. Our guide on how much dry ice you need walks through the calculation.
Gel packs and water-based refrigerants
Gel packs are mostly water thickened with a polymer. They melt at about 0 °C, so they work well for refrigerated shipments when conditioned correctly, and they are cheap and not regulated. They cannot hold a payload frozen for long, because once they reach 0 °C they warm with the box. Packed straight from a freezer, they can also push refrigerated products below 0 °C.
Liquid nitrogen dry shippers
Dry vapor shippers hold liquid nitrogen absorbed in a porous material inside a vacuum-insulated vessel, keeping cell and gene therapy payloads in nitrogen vapor below -150 °C. For example, Peli BioThermal lists its reusable evo DV10 at below -150 °C with a hold time of more than 360 hours at 27 °C. Whether a specific dry shipper is treated as a dangerous good depends on its design and the carrier's rules, so confirm with the carrier and the manufacturer before booking.
Comparing temperature ranges and refrigerants
This side-by-side comparison shows how the four refrigerants differ on the criteria that drive the decision. Durations depend on the box and pack-out, so the table gives the drivers rather than fixed hours.
Criterion | PCM | Gel packs | Dry ice | LN2 dry shipper |
|---|---|---|---|---|
Temperature held | Set point by formulation, about +20 °C to -20 °C, special grades to about -70 °C | Refrigerated, around 0 °C to +8 °C when conditioned | About -78.5 °C, payloads typically below -60 °C | Below -150 °C |
Best use cases | Vaccines, biologics, reagents, clinical kits, -20 °C products | Short refrigerated parcels, specimens | Frozen biologics, cells, plasma, deep-frozen specimens | Cell and gene therapies, cryopreserved cells |
Duration driver | PCM mass and insulation | Gel mass and insulation | Dry ice mass versus sublimation rate | Nitrogen charge and vessel design |
Conditioning | Required, at set temperature for a set time | Required, refrigerate or freeze per instructions | None, packed on arrival | Charge with liquid nitrogen before shipping |
Weight and cost drivers | Higher upfront cost, freezer capacity, return freight | Low unit cost, heavy for long durations | Recurring purchase every shipment, extra mass for delays | High vessel cost, rental and return logistics |
Reusability | Reusable if undamaged | Often reusable, many shipped as single-use | Consumed every trip | Reusable vessel |
Regulatory status for air | Generally not regulated, confirm the safety data sheet | Generally not regulated | UN1845, Class 9, marking and carrier arrangements | Depends on design and carrier, confirm before booking |
Use PCM when stability at +2 °C to +8 °C, CRT or -20 °C is required. Choose dry ice when shipping deep-frozen materials, and liquid nitrogen when the product must stay below -150 °C. Mixed temperature loads usually ship in separate qualified boxes, one per range.
Can PCM packs replace dry ice?
Yes, for many shipments. PCM packs can replace dry ice for refrigerated, CRT and -20 °C payloads, and newer PCMs designed around -70 °C allow some -60 °C shipments without dry ice. For products that must stay at -70 °C to -80 °C, or colder, dry ice or liquid nitrogen remains the standard choice.
Replacing dry ice makes most sense in three cases. The first is frozen -20 °C products that were shipped on dry ice out of habit, where a -20 °C PCM holds the range without over-cooling. The second is lanes where dry ice supply or replenishment is unreliable. The third is high-volume programs where reusable PCM shippers on a return loop lower per-trip cost and waste.
PCM is a poor substitute when the product label requires -70 °C or colder, when sites cannot condition PCM at very low temperatures, or when the shipment is one-way to scattered sites and reusable packs will not come back. Any change of refrigerant needs a new qualification of the full pack-out before it goes live.
What are the alternatives to dry ice for shipping temperature-sensitive samples?
The main alternatives to dry ice for shipping temperature-sensitive samples are frozen PCM packs and eutectic plates for -20 °C and other sub-zero ranges, ultra-low PCMs designed around -70 °C for some -60 °C shipments, gel packs or +5 °C PCM for refrigerated samples, and liquid nitrogen dry shippers for cryogenic samples below -150 °C.
Choose the alternative by the sample's required range:
Refrigerated samples (+2 °C to +8 °C): conditioned gel packs or +5 °C PCM. Dry ice should never be used here.
Frozen samples (about -20 °C): -20 °C PCM or eutectic ice packs conditioned in a suitable freezer.
Ultra-cold samples (-60 °C and colder): ultra-low PCM where qualified data supports it, otherwise dry ice.
Cryogenic samples (below -150 °C): liquid nitrogen dry vapor shippers.
Several of these options also reduce hazmat paperwork for air shipments, because the refrigerant itself is not a dangerous good. The sample may still be regulated, for example as UN3373 biological substance, Category B. Our IATA biological packaging guide covers those rules.
Is dry ice or gel packs better for overnight frozen shipping?
For overnight frozen shipping, dry ice is usually better, because gel packs melt at about 0 °C and cannot keep a payload frozen for a full transit. Gel packs are better for overnight refrigerated shipping. For products that must stay near -20 °C rather than deep-frozen, a frozen PCM or eutectic pack can be a third option.
The dry ice vs gel packs decision also changes cost. Dry ice is a recurring purchase and adds dangerous goods steps for air, but a small amount in a well-insulated box keeps a payload frozen overnight. Gel packs are cheaper and unregulated, but they only make sense when the product tolerates temperatures above 0 °C. If a frozen product arrives soft after a gel pack shipment, the refrigerant was wrong for the range, not just undersized.
Are PCM cold packs reusable?
Yes. Most PCM cold packs are reusable if they are intact, cleaned and re-conditioned at the specified temperature for the specified time before each shipment. Reuse depends on the pack staying sealed and undamaged and on a return path that brings packs back.
Packaging durability and reuse
PCMs usually come in durable gel or wax form, sealed in flexible pouches or rigid panels. They resist punctures and can serve many shipments, which reduces waste and packaging cost over time. They do need a freeze or refrigeration cycle before each use, conditioning space sized to your shipping volume, and inspection for leaks. Some reusable shippers integrate PCM into the box itself and are refurbished and re-conditioned by the manufacturer between uses.
Dry ice cannot be reused, because it sublimes away in transit. The box around it can be reusable, as with reusable dry ice shippers, but new dry ice must be added for every trip. Packages must be vented so gas can escape, and handlers need training and protective equipment.
Regulatory considerations
Dry ice is regulated as a dangerous good for air transport. Refrigerants such as PCM and gel packs generally are not, although you should confirm with the safety data sheet. Highway shipments of dry ice are generally not subject to the dangerous goods rules, but most express parcels end up on aircraft, so plan for air rules.
Dry ice rules for air shipments
In the United States, 49 CFR 173.217 sets the requirements for carbon dioxide, solid (dry ice). The key points for air shipments are:
Packaging must be designed and constructed to permit the release of carbon dioxide gas.
The net mass of dry ice must be marked on the outside of the package.
The shipper must make arrangements with the operator for each shipment.
Dry ice is excepted from shipping papers if alternative documentation gives the proper shipping name (Dry ice or Carbon dioxide, solid), Class 9, UN 1845, the number of packages and the net quantity in each.
Up to 2.5 kg (5.5 lb) per package used as a refrigerant is excepted from most other requirements if the package vents and is marked "Carbon dioxide, solid" or "Dry ice", with the name of the contents being cooled and the net weight of dry ice or an indication that it is 2.5 kg or less.
Dry ice used to refrigerate materials shipped for diagnostic or treatment purposes has its own exception from shipping paper and certification requirements, with specific marking.
The FAA's dry ice fact sheet adds that quantities above 2.5 kg per package are fully regulated as dangerous goods, with hazmat employee training and additional marks and labels. For international air shipments, the IATA Dangerous Goods Regulations apply, with dry ice covered under Packing Instruction 954. Carriers can add their own limits, so check the carrier's current rules before booking. Our guides to dry ice shipping instructions and dry ice packaging and labeling cover the steps in order.
Cold chain shippers for hazmat
Some shipments combine a regulated refrigerant with a regulated product, such as a dangerous goods sample on dry ice. Cold chain shippers for hazmat must meet the packing rules for both the contents and the refrigerant, and the outer package needs the marks and labels for each. Our guide to shipping hazardous materials covers training and documentation.
Dry ice for pharmaceutical applications
Dry ice for pharmaceutical applications follows the same transport rules, plus the shipper's quality requirements. Temperature data must still be recorded and reviewed. Where electronic records are used, see our guide to 21 CFR Part 11 for pharmaceuticals and FDA temperature monitoring. Dry ice-cooled packages should carry a logger rated for ultra-low temperatures, and the shipper should plan dry ice top-ups on long lanes.
Cost and sustainability
A PCM solution involves a higher upfront investment per pack. Multiple reuse cycles can bring the per-trip cost down, and there is less refrigerant to buy and dispose of. Conditioning freezers, labor and return freight sit on the other side of the ledger.
Dry ice is inexpensive per shipment but must be bought again for every use and sized for delays, which adds recurring cost and package weight. Supply can also tighten in summer, which Kaneka cites as one reason for developing its -70 °C PCM.
Cold chain packaging that reduces dry ice usage is a middle path. Better insulation slows sublimation, so less dry ice is needed for the same duration. Peli BioThermal, for example, states that its Crēdo Cube Dry Ice reduces dry ice usage by 75% compared with traditional solutions. Treat such figures as manufacturer claims and confirm them in your own qualification. The overall environmental benefit of switching depends on reuse rates, return distances and conditioning energy, so compare full life cycles rather than refrigerant alone.
Technical performance overview
Thermal buffer consistency: PCM holds a narrow range near its set point, which limits peak exposures.
Deep-freeze capacity: dry ice delivers ultra-cold conditions quickly, but uneven placement or partial sublimation can create temperature gradients inside the box.
Validation protocols: both PCM and dry ice pack-outs need qualification against summer and winter profiles, followed by performance checks on real lanes. Dry ice systems also need carrier-specific procedures for marking and acceptance.
Qualification of the whole packaging system is covered in our guide to pharmaceutical cold chain packaging.
Packaging selection framework
When choosing between PCM and dry ice, work through these factors in order:
Target temperature range: need +2 °C to +8 °C or CRT, use PCM or conditioned gel. Need -20 °C, use -20 °C PCM or eutectic packs. Need -70 °C or colder, use dry ice unless an ultra-low PCM is qualified. Need below -150 °C, use a liquid nitrogen dry shipper.
Shipment duration: for shorter lanes PCM works well. For long deep-frozen lanes beyond about four days, plan extra dry ice, replenishment points or a high-performance shipper.
Regulatory complexity: PCM avoids dangerous goods steps for the refrigerant. Dry ice is viable if your team is trained and your carrier accepts it on the lane.
Budget and sustainability goals: reusable PCM lowers long-term refrigerant cost and waste when packs come back. Dry ice has a lower initial cost but recurring expense.
Mercury's role in cold chain packaging
Mercury describes itself as packaging-agnostic, working with validated thermal shippers from manufacturers including CCT, Peli BioThermal, Tower and cSafe, and selecting systems by transit duration, temperature range and product requirements. Its cold chain shipping service covers refrigerated, frozen on dry ice, controlled room temperature and cryogenic shipments using liquid nitrogen dewars.
For dry ice lanes, Mercury plans routes around dry ice and coolant replenishment availability at each transit point and offers dry ice replenishment for longer shipments. Before departure, its OK-to-Send review checks each shipment against regulatory and packaging requirements, and shipments are monitored for temperature and location in transit.
Final thoughts
PCM and dry ice are not competitors for every shipment. PCM offers reusable, unregulated control from CRT down to -20 °C and, increasingly, to about -60 °C. Dry ice remains the practical choice for most deep-frozen payloads, and liquid nitrogen covers the cryogenic range. Match the refrigerant to the product's range first, then to the lane, the rules and the cost.
To plan the refrigerant for a specific lane, share the product range, payload and route with Mercury through the Mercury contact page.
