Dry Ice (UN 1845): Rules That Keep Frozen Shipments Frozen

Dry ice keeps samples at approximately −78.5 °C, which is why −80 °C freezers' contents ship on it. It is also a Class 9 dangerous good — UN 1845 — with its own packing instruction (PI 954), quantity declarations, and ventilation requirements that exist because CO₂ displaces oxygen in aircraft holds.

The rules that matter

• Declare net dry-ice weight per package; carriers limit it per booking and it differs between them
• Packaging must allow CO₂ venting — never seal dry ice airtight
• Budget sublimation for the full realistic transit: connections, customs holds, weekend receiving gaps
• Frozen biological substances usually travel as UN 3373 + UN 1845 together — two compliance layers, one box
• Airlines require staff who offer dry ice for transport to be trained under IATA DGR

We size dry ice for the route as it actually runs — including the ugly scenarios — and declare it correctly. Warm arrivals are rarely the ice's fault; they are the math's.