Going away for a few days to a place with severely limited fridge space. Normally we just start with ice, drain, buy a few more bags of ice. It does make for some soaking/ wet stuff issues every year.
Can I put chunks of dry ice into zip loc bags, and would they last any shorter or longer for NOT being exposed to the air in the hard plastic cooler?
Check YouTube for dry ice bombs. A ziplock bag wouldn’t die so spectacularly, but it would do so much sooner.
Won’t last significantly longer than if they were just exposed in the cooler. If the bag is sealed it will pressurize and burst eventually as mentioned above. The melting dry ice won’t get anything wet though, it just turns into CO2. Wrapping the stuff in a towel is one way to go, the towel will absorb and moisture in the cooler and freeze from the dry ice.
If your objective is to make the dry ice last longer, the best way to do that is to insulate it, which you could achieve by wrapping it in layers of bubble wrap and/or foam packaging, and/or expanded polystyrene, or, I guess, putting it in a vacuum-insulated flask, as long as you vent the lid, because, yes, dry ice bombs.
The more you insulate it, the less heat it will absorb, and the longer it will last - of course it doesn’t provide any significant cooling capacity when it’s insulated, because ‘absorbing heat’ and ‘cooling other stuff down’ are the same thing - but I’m assuming your plan is to use some dry ice now, and try to save some other dry ice to use later, when the first lot is exhausted.
Or you can just put the food you want to keep cold inside the insulation with the dry ice, too.
Maybe he could put the dry ice under a layer of “do not eat” silica packs.
(Having played with dry ice before (yes, one use was dry ice bombs) I can confirm that a crust of water ice from the atmosphere forms around it–but probably not enough to damage food, especially you put the food in the ziplock bags instead.)
Another advantage is that the cold CO2 will fill the box and help reduce other warmer air from infiltrating in.
I’d go with the best way to make the dry ice last longer is to get a bigger block of it … not just because more lasts longer (duh) but because less surface area per volume. Better one big block than two smaller blocks of the same volume.
The towel wrap is also a “cool” idea.
Also, if you are going to be driving with that in your car, better keep a window rolled down.
Dry ice also will freeze what you are storing as opposed to keeping it chilled.
Perhaps even inside some kind of specialized box designed to insulate food from outside heat. 
!!!
Now, LISTEN here.
Hard plastic cooler, good sized. I swear…
Good idea to avoid the explosions.
Perhaps tonfind some dry ice locally up at the lake. Dump out the half-melted ice. Get an old towel.
If things start to freeze I’ll know it.
We leave our coolers on the porch. Zero sunlight but outside.
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So your problem is that stuff in your cooler is getting wet. And you have zip-loc bags.
Why don’t you put the stuff you don’t want to get wet in the zip-loc bags? No need for dry ice at all.
How about regular ice and a Styrofoam cooler. I’ve had I’ve last days in Styrofoam, much longer than in a plastic cooler. A bit noisy though.
I often transport stuff over dry ice for work, and I’m careful to put the cooler in the trunk rather than the backseat.
Car trunks aren’t vented to the outside though, are they? I thought the trunk was basically open to the interior of the car.
Dry Ice really comes into its own on long trips, when carrying lots of food. Meats and things like ice cream that need freezing and need to stay frozen, and should not get wet go into a cooler with dry ice. It shouldn’t need to be opened very often. Drinks and things that need to stay cold but not frozen go into other coolers. This works really slick. Around here, the only place to buy dry ice is at a car wash. I have no idea why, but they have it.
I’ve had ice last for a long weekend by getting a block of ice – hard to find nowadays in some places, but available in others – and a slab of dry ice. The dry ice goes in one end of the cooler, the block in the middle, and the food on the other end. Keeps food and drinks plenty cold without freezing any of it.
This was over Labor Day weekends with high temps in the 80’s-90’s. I would set up the cooler on Friday morning. Sometime Saturday afternoon the dry ice would be gone, at which point I’d have the full block of ice, plenty cold. Come Monday afternoon about a third of the block would be left.
Of course there would then be ice melt, but that could be handled by draining and/or keeping things off the bottom of the cooler with some sort of spacer.
Um wow I had no idea that was the case.
There certainly seems to be some difference in temperature in my experience (e.g. if I’m driving with a heated car on a winter day, the trunk is colder) so I think/hope that there’s some partial though not complete separation of the airstreams.
I’ve had dry ice last for two and a half days, but you need a fairly large quantity.
I like the wet ice / dry ice concept. Only once on location.
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