USING DRY ICE
Plan on using 5 to 10 pounds of dry ice per day, depending upon the ice chest size. Dry ice will keep everything frozen in this ice chest, including extra ice, so consider refrigerating non-frozen goods with regular ice in a separate ice chest. Dry ice sometimes comes in 10-inch squares, 2 inches thick, weighing about 10 pounds each square. Plan to put one square per 15 inches of ice chest length. For a forty-quart cooler, use two squares or 20 pounds. If you can only get pellets, separate them into 10-pound paper bags to spread them around and keep them from falling to the bottom. Do not seal plastic bags tight, or they will burst. At -109°F or -78°C, dry ice will freeze and keep everything frozen in its container until it is gone. These frozen items will take extra time to thaw because they have been so cold.