That lid will release its self if the dry ice is still in there ! POP ! I can see a comedy skit in that (Ha Ha)!

You may need to check that the dry ice doesn't "burn" any food that it is in contact with. When I've used it in the past, mostly for meat storage, we always wrapped it in paper to stop this happening.

But dry ice would be an interesting comparison to the hand warmers. By the way, you can store dry ice for a few days in foam box in a domestic deep freeze – it won’t keep too long, but if you don’t use it all immediately you can prolong its life a little.