Dry ice is solid carbon dioxide and passes directly to gas at about -78 °C without becoming liquid. The gas is heavier than air; in a closed vehicle, a lift or a small store it collects near the floor and pushes oxygen out. The symptoms are headache, dizziness and loss of attention, and by the time someone notices they are often past the point of reacting. NIOSH limits are 5000 ppm (0.5 percent) as a ten-hour average, 30,000 ppm for short-term exposure and 40,000 ppm as the level immediately dangerous to life. Dry ice on skin causes a cold burn within seconds, and in a sealed container where the gas finds no way out, pressure can split the vessel.

By road, ADR section 5.5.3 applies. Packages must let the gas escape and the vehicle must be well ventilated, meaning carbon dioxide stays below 0.5 percent and oxygen above 19.5 percent. Ventilation is not required if the load compartment is separated from the cab against gas exchange or is an insulated, refrigerated body, but the doors then carry a WARNING mark. Unpackaged dry ice must not touch the vehicle's metal body; at least 30 mm of separation is left. By air, the IATA 2026 acceptance checklist looks for the UN1845 and Dry ice marks, the net mass per package, the Class 9 label, no more than 200 kg per package and packaging that vents gas and conforms to Packing Instruction 954.

Before dispatch, put these in writing:

  1. The product's approved temperature range accepts dry ice; at -78 °C it can freeze a 2-8 °C product.
  2. The packaging lets the gas out and is not sealed airtight.
  3. The net dry ice quantity was weighed and entered in the dispatch record, not estimated.
  4. The box with dry ice does not ride in the driver's cab; doors are opened and aired before loading and unloading.
  5. Staff use insulated gloves and eye protection and their training is recorded.

Leftover dry ice is left to sublimate on its own in a ventilated area; it does not go into a sink, a toilet or a waste container. If gas exposure is suspected the area is left, and with damaged packaging or a temperature excursion the product is set aside and not released without a quality assessment.