Styrofoam coolers are often used to transport frozen or refrigerated goods with the use of dry ice. But how long does dry ice last in a styrofoam cooler, when does it run out and are there ways you can make it last longer?
Dry ice lasts approximately 18-24 hours in a regular sized styrofoam cooler with 1-2 dry ice blocks. Dry ice can last up to 3 or 4 days in a larger cooler and when more blocks of dry ice are used in conjunction with each other.
Dry ice is frozen carbon dioxide and it is around -109.3°F (-78.5°C) which is much colder than regular ice which is only 32°F (0°C). A standard freezer is usually set to 0°F (-18°C) so dry ice is even colder than a freezer.
Dry ice also turns directly from a solid into a gas so it doesn't make anything wet or leave any mess.
What Affects How Long Dry Ice Lasts in a Styrofoam Cooler?
How long the dry ice lasts in your styrofoam cooler depends on a variety of factors. This is similar to how long regular ice lasts in a styrofoam cooler and all of these factors play a role into how long the dry ice will last.
Amount of Dry Ice Used
If you use just a small amount of dry ice then it will not last very long in your cooler. Maybe a couple of hours at best.
But if you use a lot of dry ice then it can actually last days.
This is because more overall heat is required to completely turn all of the dry ice into gas. The less dry ice there is the less overall heat is required.
So if you want your dry ice to last longer than use more of it.
Thickness of the Styrofoam Cooler
Styrofoam is a good insulator because it has millions and even billions of tiny air bubbles which work to stop heat transfer.
The thicker the cooler the more insulating ability it has and the longer the dry ice will stay frozen for.
This is why coolers like Yeti have up to 3 inches of insulation and can keep ice for days or even weeks at a time. See the best coolers for ice retention.
So using a thicker styrofoam cooler will make your dry ice last longer. If you don't have a thicker cooler you can put one cooler inside another or you can break off bits of styrofoam and glue/tape them together to make it thicker.
Amount of Produce The Dry Ice Is Keeping Cold
The more product you are trying to keep frozen the more dry ice you will need. A lot of dry ice with a little bit of food will last a long time but won't be cost effective.
A little bit of dry ice with a lot of food won't last very long at all.
This dry ice calculator is a helpful too for shipping.
Is The Dry Ice On The Top or Bottom
If you put the dry ice on the top of your cooler then it will disappear faster than if you put the dry ice at the bottom of your cooler.
This is because it is exposed to more heat near the top of the cooler and as the cold air sinks it moves away from the dry ice allowing it to warm up faster.
If you put the dry ice on the bottom the cold air will mostly stay down in the dry ice and less heat will get to it making it last longer.
Amount of Empty Space In The Cooler
Empty space or air is your enemy when trying to make dry ice last as long as possible. I learned this when I researched how long a Yeti cooler stays cold.
If you have the same amount of dry ice then putting it in a smaller cooler with less air space will make it last longer than a large cooler with lots of air space. The air makes the dry ice sublimate faster.
How To Make Dry Ice Last Longer In a Styrofoam Cooler
If you're shipping something a long way or you want to make absolute sure that the dry ice lasts as long as humanly possible here are some tips on how you can make dry ice last longer in a styrofoam cooler.
Use More Dry Ice
The more dry ice you use the longer it will last. Dry ice usually comes in 1 pound bags or you can get larger 5 lbs bags or even large quantities from specialty suppliers.
1 pound will stay frozen in a styrofoam cooler for 12-24 hours, but the below video shows someone keeping dry ice for about 2 days and in the video they say when they used 28 lbs of dry ice it lasted “several days” in the cooler.
Cover It With Cardboard or Newspaper
Covering your dry ice with cardboard or newspaper actually helps to insulate your dry ice from the warmer things in your cooler. It also stops the gas being taken away from the ice as quickly.
By wrapping your dry ice in newspaper or by putting a layer of newspaper or cardboard on the top and bottom of your dry ice blocks it will last longer.
It's also a good idea to keep the dry ice in the plastic bags they come in as this plastic is also an insulator and will make the dry ice last a little bit longer.
Use a Thicker Cooler
As we mentioned above the thicker your styrofoam cooler the more insulating power it has and the longer the dry ice will last.
This is why coolers like Yeti with 2-3 inches of insulation can keep dry ice easily for 2-3 days or even longer even when only a small amount is used.
So get a thick styrofoam cooler, stick one styrofoam cooler inside another or stick extra pieces of styrofoam onto the walls of your cooler to make it thicker if you want the dry ice to last longer.
Combined With Water Ice or Gel Packs
If you add water ice or pre-frozen gel packs then not only can this fill up empty space in your cooler but it can also continue to keep the produce in the cooler cold for hours or days after all the dry ice is gone.
The dry ice will disappear first, but it will have kept the water ice frozen. It will then take more time for the water ice to melt, all the while keeping your food cold.
Freeze Items Before Putting Them In Your Cooler
If you put room temperature items into the cooler this will cause the dry ice to disappear more quickly as heat from your items will warm up the dry ice.
To stop this pre-freeze everything before putting it in the cooler with the dry ice.
Line Your Cooler With Aluminium Foil
Styrofoam is good at insulating against heat conduction, but it's not very good at reflecting heat radiation.
This gets a bit technical as there are multiple types of heat but aluminium is great at reflecting radiant heat.
So combining styrofoam and aluminium foil will make your cooler a more effective insulator. So line the inside or outside of your cooler with aluminium foil for better insulation and to keep your dry ice longer.
Important Considerations When Using Dry Ice In a Styrofoam Cooler
Dry ice isn't the same as regular ice and there are some important considerations you need to think about when handling it, packing it and using it for the shipping and storing of cold goods.
Don't Completely Seal It
Dry ice turns directly from a solid into a gas. This means it is constantly expanding and the gas needs a way to escape otherwise your cooler can explode.
So make sure there is a way for all that pressure that is being built up to escape and don't make your cool air tight.
Don't Handle The Dry Ice With Your Bare Hands
Dry ice is super cold and at -109.3°F (-78.5°C) it can actually cause frostbite if you don't handle it with care.
Avoid using your bare hands and use gloves where possible or handle it with a cloth or plastic or some other insulator.
Also try not to handle it for long periods of time to minimise your exposure to the cold.
Don't Put Food Directly on the Dry Ice
Putting food, especially meat, directly on the dry ice can make the food so cold that it ruins it. Meat can get freezer burn which makes it tough and destroys it's taste.
Instead use a layer of cardboard, plastic or newspapers between the dry ice and your food to add some insulation and stop your food from getting so frozen it's ruined.
Don't Use Dry Ice With Soda/Drinks
Dry ice is so cold that it is going to quickly freeze any drinks you put in your cooler, unless those drinks are kept well away from direct contact with the dry ice.
This will cause the drinks to freeze, expand and possibly even cause the can/bottle to break or explode.
This is especially true for soda cans as these expand A LOT when frozen. So be careful using dry ice with drinks.