During a recent mountain hike, we were asked about hot packs; are they any good? are they bad for the environment?
They seem to be everywhere in Korea, and from our perspective, their use is far more widespread here than in other countries.
Are they any good?
Sure; they'll keep your fingers warm - though their effectiveness is greatly dependent on the brand you buy.
Are they the best option though? For activities like skiing, or climbing, where there are extended periods of inactivity in a cold environment, they can be very useful - but there are plenty of alternatives. You can use hot drinks or a more effective system of layering up and down with your thermal-wear.
For hiking, we don't really see the appeal; you're near constantly in motion except for one or two extended breaks where you are eating or able to set up some kind of a shelter.
Are they bad for the environment?
Certainly they are if you discard the plastic packets as pictured above.
The packs themselves are surprisingly harmless (ignoring the manufacturing and packaging - and everything else involved in their distribution - an argument that can be raised against whether the production of anything is essential or not?) - they are mostly commonly made with natural elements that breakdown without issue.
Their usage here is non-essential, and we'd recommend selecting more appropriate clothing for your activity. If the cold is something you really suffer from, then we wouldn't chastise you for taking them out, but like a lot of outdoor activities - you are sometimes best served by hardening yourself to the elements.
And if you do take them out, bring them back with you and discard them responsibly. The mountains in Korea really don't need any more trash.