Coolers packed with ice help to keep perishable foodstuffs safe for a longer time. Both dry ice and regular ice are effective cooling agents.
Food spoils soon in the heat. Lower temperatures help keep the bacteria away. Coolers are the safest means of transporting food on road trips and railway journeys.
Dry ice is frozen carbon dioxide. The temperature of dry ice is -109.3°F (-78.5°C). Handling dry ice requires insulated gloves because the extreme cold can cause frostbite. Regular ice is frozen water. Water starts to freeze at 0°C (freezing point) or 32°F. Regular ice is not as cold as dry ice, and can be handled without gloves or tongs.
The most efficient packing method is to put dry ice on top of items in a cooler, because as cold sinks it cools everything in its path. Pound for pound, dry ice gives more than twice the cooling energy of regular ice. Dry ice keeps frozen food frozen.
Regular ice is the more traditional cooling medium. Once ice starts to melt, its cooling efficiency reduces. Also, it melts to water and creates puddles in the cooler.
Dry ice sublimates--changes directly from solid to gas, with no intervening liquid state. However, as it changes to carbon dioxide gas it expands, which can cause an airtight container to explode. Dry ice requires adequate ventilation because the carbon dioxide can cause breathing difficulty. Regular ice does not need extra precautionary measures. Regular ice packed between dry ice stays frozen longer.
