so cold it freezer burns.

Air is only 0.04% CO2 but 78% nitrogen. I propose we standardize liquid nitrogen as the de facto portable, single-use coolant over grocery store dry ice.

Instead of cooling the whole room it’s more efficient to cool individual people though. Which means taking advantage of their sweat’s evaporation would make more sense. So like those reflective Japanese jumpsuits with fans at the bottom and outlets at the top are probably the best design. A little evaporating or sublimating gas in the suit couldn’t hurt though (depending on where the reservoir is held).

You can make reusable ice packs with some liquid dish soap, water, and a hand towel/big towel and some type of ziplock bag; though the vacuum seal food bags are much more reliable.

The dish soap allows it to remain pliable so it can be molded into you. And the custom sizes and shapes allow you to place it usefully- big flat ones on the spine is ooo-la-la. If you need to cool off in a hurry? Long ones under the arm pits, shins, fore arms and around thighs, too.

Easy change is a longer, some what wide shape that you can fold around your neck, kinda like a scarf.

Aren’t these people like 140 years old now?