Dry ice sublimes at -78.5 °C: it turns to gas without becoming liquid, and it does so from its surface. That is why the life of a kilo is set by its surroundings rather than by the ice itself. In the 2006 report by the US Federal Aviation Administration (FAA) only the pellets in a foam box are the report's own measurement; for paper-wrapped small blocks (1977) and a single 45 kg block (1963) it quotes two earlier studies. The fourth row is your own container.
| Condition | Loss per hour | What it means for 1 kg |
|---|---|---|
| Paper-wrapped 0.5 and 2.3 kg blocks, cabin of a small parked aircraft at 22 °C (1977 study) | 14 per cent | Gone in about 7 hours |
| 2.3 kg of pellets in a 38 mm foam box, 22-29 °C (the FAA's own measurement, 2006) | 2 per cent (1.6-2.9) | 45 g per hour; 1 kg in the same box, by calculation, about 22 hours |
| A single 45 kg block (1963 study) | 1 per cent | Little surface for its mass |
| Your container and load | Found by weighing | See the measurement below |
Pellets expose far more surface than a block of the same weight, so pellets suit fast cooling and blocks suit long jobs. In a half-empty container every lid opening lets the cold gas flow out; in a full one the product's own cold supports the ice.
To find your own duration, prepare the container with its real load, add weighed dry ice and weigh again every few hours. Grams lost divided by hours elapsed is that container's hourly consumption; summer and winter, blocks and pellets are measured separately.
