My friends and I are going backpacking and want to keep a single item cold for 2-3 days. Freezing is not a problem - preferably the closest to being frozen as possible. It is medication that may be needed in case of emergencies. It's about the size of a large snickers

Our idea is to buy some kind of snap-cold pack and place our belongings in a small cooler filled with ice water. We only have to carry this stuff for 2 days, max, so the weight won't be too big of an issue.

Are there better was of approaching this? What gel packs have backpackers used?

  • What size item? Perhaps a thermos container and dry ice?
    – jamesqf
    Jul 24, 2015 at 1:12
  • @jamesqf thermas container would be perfect sized, if it would stay cold that long! It's about the size of a large snickers.
    – Welsh4588
    Jul 24, 2015 at 1:53
  • @jamesqf how long would dry ice keep he thermos cold?
    – Welsh4588
    Jul 24, 2015 at 1:54
  • How cold is cold? What is the item? Dry ice will freeze it, Is freezing a problem?
    – user5330
    Jul 24, 2015 at 4:30
  • 2
    I'm pretty sure that a thermos (vacuum flask) is going to keep it cold longer than any other non-active cooler. I don't know how long, precisely, but they're used for transporting e.g. small quantities of liquid nitrogen: physics.stackexchange.com/questions/73803/… Best idea would be to try one before you leave on the trip - fill one with ice cubes, say, and let it sit outdoors.
    – jamesqf
    Jul 24, 2015 at 5:13

3 Answers 3


One suggestion, which you will need to try by experiment - dry ice on the bottom of a Thermos. Pack some layers of insulation on top of the dry ice, and put the item on top, with a thermometer so you can keep an eye on temperatures. Adjust the insulation to get the temperature sitting where you want it. The thermometer can be checked though the trip and insulation adjusted if needed.

Do not seal the thermos tight - the dry ice is CO2, and the gas released as it evaporates needs to escape or pressure will build up.

Normal Ice might last a few days in a good Thermos, but its melts to water - the container the item is is need to be water proof and thermo needs to be sealed. Its unlikely you will be able to maintain below freezing for much more than a day.

As far a Thermos goes, a glass vacuum one is usually the most efficient and relatively light, but prone to breakage. If a stainless steel one keeps the item cold enough for the time, it would be my preference. Bigger will hold more dry ice and stay cooler longer than a smaller one.

  • I didn't think ice would even last that long! I appreciate the suggestion, and I'll definitely be looking into this. Thanks!!
    – Welsh4588
    Jul 24, 2015 at 12:38

The type of medication being transported can impact the answer to this question. But for Insulin a really good choice is FRIO cooling case it use evaporation to keep the contents cool. It needs to be someplace it can breath so in the center of your back pack is not a good choice, but an outside pocket might be a good choice.

It can be used over and over again and can be recharged on the trail. We have used it extensively for day and week trips.

It is not the solution for all meds, so as suggested in the FAQ check with a medical professional about the requirements of your specific medication.

Can a FRIO® be used for other medication?

Yes, FRIO® wallets can be used for other medications that can be stored at room temperature. We strongly recommend that users of medication other than insulin ask their GP, pharmacist or the medication's manufacturer for the safe travel data/safe travel allowance of their medication.

Note: the wallet does not keep medication as cold as a 'fridge' would (2-8°C (35.6-46.4°F)), but it does keep medication cool within safe temperatures of 18-26°C (64.4-78.8°F) for 45 hours minimum, even in a constant environmental temperature of 37.8°C (100°F).


Last week, I backpacked into Idaho's White Cloud Mountains. I boiled a few eggs the night before and placed them in the refrigerator. On the morning we left, I took them out and rolled them up in a t-shirt and tucked them under a jacket in my pack. They were still very cold the next morning and cold enough on the second morning.

Daytime temperatures were around 80 and it got down in the 40's at night. They spent the night with the other food about 12 feet off the ground.

I'm sure that a small brick of frozen Blue Ice would've kept them cold for at least one more day.

Sealing the food and ice in a bag, then wrapping your sleeping bag around it would probably work really well.

  • I enjoy this method.. Will test this tomorrow and get back and see how that worked! Thanks for the advice
    – Welsh4588
    Jul 27, 2015 at 11:58

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