How to ship refrigerated products.
Cold-chain shipping has one rule: start cold, stay cold, all the way to the door. Miss it and food spoils, pharmaceuticals fail, and a shipment becomes a loss. Here is how to keep refrigerated and frozen products safe in transit — the coolants, the trade-offs, and the packaging that holds the temperature.
Ensuring food safety
Everything about cold shipping comes back to one idea: keep perishables out of the temperature danger zone. Bacteria multiply fastest in the range between refrigeration and warmth, so the job is to hold food either properly chilled or fully frozen from the moment it leaves your hands until it reaches the customer.
That starts before the coolant goes in. Pre-chill or freeze the product and the packaging, so you are not asking the coolant to do the initial cooling on the road. Size the coolant to the whole transit time with a margin — under-packing is the most common cold-chain failure. And pick the fastest reasonable service: the less time a shipment spends in transit, the less cold you have to carry. Cold shipping is a race against the clock, and every hour of transit is an hour the temperature can drift.
Shipping with dry ice
Dry ice is the coolant for anything that must stay frozen. At roughly −109 °F it is far colder than water ice, and because it sublimates straight to gas it leaves no meltwater to soak packaging or spoil texture. Drop it into a well-insulated box and it keeps ice cream, seafood, meat and frozen prepared foods solid across the country.
The trade-offs are its extreme cold and the gas it gives off. Keep a barrier between dry ice and any unwrapped food so it does not freeze-burn the product, and place it on top of the load, since cold air sinks. Because it sublimates — losing several pounds a day — size it to the trip and over-pack a longer one. And never seal it in an airtight container: the CO2 gas needs to vent.
Handle dry ice safely
Use insulated gloves. Dry ice causes cold burns on contact — never handle it with bare hands.
Vent, never seal. As it sublimates it releases CO2 and builds pressure; always use vented, insulated packaging.
It’s regulated in transit. Dry ice is a DOT Class 9 material with marking and quantity rules, especially by air — a freight partner handles that compliance.
Shipping using cold packs
For products that must stay chilled but not frozen, gel and cold packs are the right tool. They hold a refrigerated range rather than a frozen one, which makes them gentler on perishables — fresh produce, dairy, many pharmaceuticals and prepared meals that would be damaged by dry ice’s deep cold.
Freeze or chill the packs fully before use, and surround the product on all sides — bottom, sides and top — so the cold envelopes the load rather than cooling one face of it. For longer transit or borderline temperatures, combine gel packs with dry ice in the same box: dry ice for the deep cold, gel packs to buffer the product from it.
Choosing the right cold packs
Not all coolant packs are equal. Match the pack to the product and the trip:
- Gel packs — flexible and reusable, they hold a refrigerated range and mold around irregular products. Best for chilled goods on short-to-medium transit.
- Phase-change packs — engineered to hold a specific target temperature for longer, useful for temperature-sensitive pharmaceuticals and precise cold-chain windows.
- Foam or hard cold packs — rigid and durable, they double as structural support inside the box while adding cooling.
The variables that decide quantity are the same every time: how cold the product must stay, how long it will be in transit, the outside temperature along the route, and the insulation of the container. When in doubt, add more coolant — the cost of an extra gel pack is nothing next to a spoiled shipment.
Packaging materials that hold the cold
The coolant only works if the packaging keeps it in. The right materials protect both the temperature and the product itself.
Glass
Glass containers protect contents and resist odors and moisture, but they are heavy and can shatter under the rough handling of a freight network. If you ship in glass, cushion each piece well, keep it away from direct contact with dry ice (thermal shock can crack it), and consider whether a durable plastic alternative would survive the journey better.
Plastic bags and wrappings
Sealed plastic bags and wraps keep moisture out and contain any leaks, protecting both the product and the insulation around it. They are also the barrier that keeps unwrapped food from touching dry ice directly. Use food-grade materials, and double-bag anything that could leak onto a cold pack or the box.
Shipping containers and insulation
The outer container is where cold-chain shipping is won or lost. Use an insulated box — foam coolers, insulated liners or purpose-built cold-shipping cartons — sized to the load with no large empty voids for warm air. Insulation thickness should match the transit time: a two-day trip needs more than an overnight one. The tighter and better-insulated the container, the less coolant you burn and the safer the product arrives.
Parcels, or a refrigerated truck?
At some point, packing individual insulated boxes stops making sense. Small volumes and one-off shipments are perfect for insulated parcels with dry ice or gel packs — you control the cold precisely and ship through normal channels. But as the volume grows, the coolant, the insulation and the labor add up, and the risk of a single warm box in the batch grows with it.
That is where a temperature-controlled reefer trailer takes over. A reefer holds a set temperature end to end, so an entire load stays in range without per-box coolant — the efficient, reliable choice for pallet-scale frozen or chilled freight. The right answer depends on your volume, your transit time and how tightly the temperature must be held. If you are not sure which fits, that is exactly the kind of thing to talk through before you ship: the goal is the cheapest method that keeps every unit safely in range to the door.
Refrigerated shipping questions
The questions we hear most about keeping a shipment cold from dock to door.
Dry ice or gel packs — which should I use?
Use dry ice for products that must stay frozen, and gel or cold packs for products that must stay chilled but not frozen. Dry ice sits at about −109 °F and will freeze anything near it; gel packs hold a refrigerated range and are gentler on perishables like produce or certain pharmaceuticals. Many shipments use a combination, matched to the transit time.
How do I keep food safe when shipping it cold?
Start cold, stay cold: pre-chill or freeze the product and the coolant, use an insulated container sized to the load, add enough coolant for the full transit time plus a margin, and choose the fastest reasonable service so the cold has less time to fade. For anything spanning the food-safety danger zone, over-pack the coolant rather than cut it close.
Can I ship refrigerated freight in bulk?
Yes. Small parcels use insulated boxes with dry ice or gel packs, but larger volumes move in a temperature-controlled reefer trailer that holds a set temperature end to end. RS Group handles both — small cold parcels and full refrigerated freight — and can supply the dry ice for the shipment as well.
Shipping something that has to stay cold?
From insulated parcels with dry ice to full refrigerated freight, we keep the cold chain intact — and we can supply the dry ice too. Tell us what you're moving.