Dry ice is extremely cold and at -109.3ºF (-78.5ºC) it quickly sublimates (turns into a gas) at room temperature. If you want to keep your dry ice for any length of time you're going to need to store it effectively otherwise it'll all disappear.
Dry ice is best stored in heavily insulated coolers and packed tightly to reduce sublimation. Small quantities of dry ice can be stored in vacuum insulated containers if there is a way for gas to vent. A regular freezer will not keep dry ice frozen but there are laboratory freezers that can.
When dry ice is made in bulk it is immediately placed in an insulated cooler in order to protect it from the outside heat and keep to frozen and stop it from sublimating as quickly.
The better the cooler and the more dry ice stored the longer the dry ice will last overall. At dry ice manufacturing facilities extremely large coolers are filled with dry ice before they are send out to customers.
No matter how good the cooler is dry ice will eventually turn into gas at atmospheric pressures. A good cooler and good packing just slows down this process.
Dry ice needs to be tightly packed to minimize exposure to the outside air which speeds up sublimation. Dry ice pellets will sublimate faster than larger dry ice blocks for this reason.
Dry ice is not stored for very long in dry ice manufacturing facilities. It is made and then quickly shipped off (within hours) to customers who will be using it.
When sold in stores like Walmart dry ice is kept in large freezer chests. While these look similar to a freezer that holds regular ice and keeps it frozen it's actually just a large cooler.
There are no compressors or refrigerants used in stores to keep dry ice frozen. Rather it is just insulated from the outside heat like how a smaller cooler works.
How To Store Dry Ice at Home
If you have purchased some dry ice for food storage, to make fog or for other reasons you'll want to store the dry ice correctly otherwise your dry ice will melt fast.
After you purchase dry ice it should immediately be placed in the bottom of a cooler and a layer of foam, cardboard, plastic or paper should be placed over the dry ice.
Ideally you should take your cooler to the store and only buy your dry ice right as you are leaving the store. Take the dry ice immediately and put it in your cooler because the longer it is left in the open air the more it will turn to gas.
You want to use a high quality dry ice compatible cooler and the better the cooler the longer your dry ice is going to last.
Keeping dry ice on the bottom of your cooler will keep it for longer as cold air sinks so this ensures it is always kept in the coldest part of your cooler.
The layer of foam, cardboard, plastic or paper protects the dry ice from the air in the cooler and also adds an extra layer of insulation. You want to keep your dry ice away from air as much as possible. More details on how to use dry ice in a cooler.
Lastly you'll want to keep your dry ice cooler in a well ventilated area. As the dry ice turns to carbon dioxide gas it can displace oxygen and become dangerous in confined spaces.
Always keep it outside or keep a window open when transporting it in a car or keeping it indoors.
Can You Keep Dry Ice In a Freezer?
Dry ice is created from exposing liquid CO2 to normal atmospheric pressures. The process cools down the CO2 creating dry ice which is extremely cold (more on how dry ice is made).
Once dry ice is created it immediately begin sublimating (or turning from a solid into a gas). Because it is so cold at -109.3ºF (-78.5ºC) there are no commercially available freezers that are able to store dry ice and stop it from sublimating.
A regular freezer only gets down to around 0ºF (-18ºC) which is not cold enough to store dry ice. The temperature of a household freezer is “hot” compared to the dry ice so the dry ice will still turn to gas even in a freezer.
In fact, keeping dry ice in a freezer will cause the internal temperature of the freezer to drop significantly and the compressor that keeps the freezer cold will turn off. So ultimately keeping dry ice in a freezer is just like keeping it in a cooler, only a cooler will keep dry ice longer.
Also, dry ice may actually break your freezer in some circumstances so you need to be careful if you're putting dry ic in a freezer.
There are laboratory freezers that get cold enough to store dry ice but these are specialized products, expensive and not really worth the cost for most people.
So while you can keep dry ice in a freezer it will only last a couple of days before it's all completely gone. More details on how long dry ice lasts in a freezer.
Store Dry Ice As Liquid CO2
If you want to have dry ice on hand and not have to order it from a dry ice manufacturer then the most effective solution for long term storage is pressurized canisters of CO2.
Chances are you've likely got one nearby in the form of a fire extinguisher but you can also buy tanks of liquid CO2 from specialty suppliers.
CO2 fire extinguishers are full of liquid carbon dioxide held under pressure. The high pressure of around 200 psi (13 bar) converts the carbon dioxide gas into a liquid.
As long as it's stored below 31ºC (87.8ºF) it'll stay in a liquid state and can be stored for years at a time.
You can then use this liquid CO2 to create dry ice on demand.
By ejecting the liquid CO2 into a material bag or tea towel covering the ejection nozzle some of the CO2 will turn to gas and some will freeze into dry ice.
The process isn't extremely efficient and in factories less than half of liquid CO2 turns into dry ice with most of it being lost as gas.
But if you want on demand dry ice then this is going to be the best solution.
How Long Can Dry Ice Be Stored For?
Dry ice can be stored for 24 hours in a regular cooler and for 3-5 days in a high end cooler. Longer than this and the dry ice will all sublimate into gas and be gone.
Extremely large amounts of dry ice can last longer than 5 days if kept in high qualities coolers, but like all dry ice at atmospheric pressure it will eventually turn into gas.
You can store liquid CO2 under pressure which can be turned into dry ice on demand for years at a time. But once the CO2 freezes into dry ice it'll naturally begin to sublimate into gas.
Are There Dry Ice Freezers?
No household freezers get cold enough to keep dry ice for any length of time however there are laboratory freezers and cryo freezers that get below -109.3ºF (-78.5ºC) and can keep dry ice in it's frozen state.
These freezers are expensive to purchase and run and so are only really used in laboratory settings.
CO2 is much cheaper and easier to store as a liquid under pressure which can then be used to create dry ice on demand.
However, given that dry ice doesn't cost much to buy it's usually most cost effective for people to buy dry ice when they need it rather than try to store dry ice for long periods of time in a super cold freezer.
How Do You Keep Dry Ice From Melting?
In order to keep dry ice from melting/sublimating you need to store it at -109.3ºF (-78.5ºC) or less. No household freezer gets this cold so to slow sublimation keep dry ice tightly packed in the bottom of a heavily insulated cooler.
How Do You Store Dry Ice In a Lab?
If you are using dry ice for experiments or to keep biological samples cold you'll want to store that dry ice so it lasts as long as possible.
To store dry ice in a lab pack it tightly into a high quality cooler and place in a well ventilated area. If you have an ultra low temperature freezer below -78.5ºC (-109.3ºF) then you can store dry ice in there and it will remain a solid.
In most circumstances it's best just to keep dry ice in a cooler where it will last for 3-5 days and replace the dry ice as required. Dry ice is not very expensive and you can buy dry ice from lots of different places, not just from medical suppliers.