Dry Ice is frozen carbon dioxide, a normal part of our earth's atmosphere. It is the gas that we exhale during breathing and the gas that plants use in photosynthesis. It is also the same gas commonly added to water to make soda water. This gas is often captured during industrial processes and recycled to make Dry Ice.
Dry Ice is particularly useful for freezing, and keeping things frozen because of its very cold temperature: -109.3°F or -78.5°C. Dry Ice is widely used because it is simple to freeze and easy to handle using insulated gloves. Dry Ice changes directly from a solid to a gas -sublimation- in normal atmospheric conditions without going through a wet liquid stage. Therefore it gets the name "dry ice."
As a general rule, Dry Ice will sublimate at a rate of five to ten pounds every 24 hours in a typical ice chest. This sublimation continues from the time of purchase; therefore, pick up Dry Ice as close to the time needed as possible. Bring an ice chest or some other insulated container to hold the Dry Ice and slow the sublimation rate. Dry Ice sublimates faster than regular ice melts but will extend the life of regular ice.
It is best not to store Dry Ice in your freezer because your freezer's thermostat will shut off the freezer due to the extreme cold of the Dry Ice! Of course if the freezer is broken, Dry Ice will save all your frozen goods.
Commercial shippers of perishables often use dry ice even for non frozen goods. Dry ice gives more than twice the cooling energy per pound of weight and three times the cooling energy per volume than regular water ice (H2O). It is often mixed with regular ice to save shipping weight and extend the cooling energy of water ice. Sometimes dry ice is made on the spot from liquid CO2. The resulting dry ice snow is packed in the top of a shipping container offering extended cooling without electrical refrigeration equipment and connections.
Dry Ice temperature is extremely cold at -109.3°F or -78.5°C. Always handle Dry Ice with care and wear protective cloth or leather gloves whenever touching it. An oven mitt or towel will work. If touched briefly it is harmless, but prolonged contact with the skin will freeze cells and cause injury similar to a burn.
Store Dry Ice in an insulated container. The thicker the insulation, the slower it will sublimate. Do not store Dry Ice in a completely airtight container. The sublimation of Dry Ice to Carbon Dioxide gas will cause any airtight container to expand or possibly explode. Keep proper air ventilation wherever Dry Ice is stored. Do not store Dry Ice in unventilated rooms, cellars, autos or boat holds. The sublimated Carbon Dioxide gas will sink to low areas and replace oxygenated air. This could cause suffocation if breathed exclusively. Do not store Dry Ice in a refrigerator freezer. The extremely cold temperature will cause your thermostat to turn off the freezer. It will keep everything frozen in the freezer but it will be used up at a faster rate. It is the perfect thing if your refrigerator breaks down in an emergency. There are also Commercial Storage Containers available.
Normal air is 78% Nitrogen, 21% Oxygen and only 0.035% Carbon Dioxide. If the concentration of carbon dioxide in the air rises above 0.5%, carbon dioxide can become dangerous. Smaller concentrations can cause quicker breathing and headaches but is otherwise not harmful. If Dry Ice has been in a closed auto, van, room, or walk-in, for more than 10 minutes, open doors and allow adequate ventilation before entering. Leave area containing Dry Ice if you start to pant and breath quickly develop a headache or your fingernails or lips start to turn blue. This is the sign that you have breathed in too much CO2 and not enough oxygen. Dry Ice CO2 is heavier than air and will accumulate in low spaces. Do not enter closed storage areas that have or have had stored Dry Ice before airing out completely.
Plan to pick up the Dry Ice as close to the time it is needed as possible. It sublimates at 10%, or 5 to 10 pounds every 24 hours, whichever is greater. Carry it in a well-insulated container such as an ice chest. If it is transported inside a car or van for more than 15 minutes make sure there is fresh air. After 15 minutes with Dry Ice only in its paper bag in the passenger seat next to me, I started to breathe faster and faster as though I were running a race. I couldn't figure out why I was so out of breath until I saw the car air system was set in the re-circulated position, not fresh outside air.
Treat Dry Ice burns the same as a regular heat burns. See a doctor if the skin blisters or comes off. Otherwise if only red it will heal in time as any other burn. Apply antibiotic ointment to prevent infection and bandage only if the burned skin area needs to be protected.
Here is a Material Safety Data Sheet available on line:
Do not leave Dry Ice on a tiled or solid surface countertop as the extreme cold could crack it.
Unwrap and leave it at room temperature in a well-ventilated area. It will sublimate from a solid to a gas.