In North America, disposable hand warmers tend to live in a ski bag or a hunting kit, and most people only think of them on the way to a cold stadium. In Korea they are an ordinary winter purchase, about as routine as a pair of gloves, and the Korean name for them, hotpack (핫팩), is a borrowed English word.
What makes the little bag of iron powder worth a closer look is how many jobs it does. It warms hands at a bus stop and a lower back at a desk, and each job calls for a slightly different type of pack and a slightly different habit.
This guide sorts out the two main types, how they work, where to buy them, where to put them and the safety rules that Korean media repeat every winter.
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| The pocket hot pack: a small winter habit that starts with one hand and one coat. |
Two Kinds of Hot Pack, Two Different Jobs
Korean hot packs fall into two practical groups: patches that stick to clothing, and pocket packs that you hold or tuck away. That split decides where each one belongs on your body.
One December 2023 news report sorted warmers into USB rechargeable ones, plastic-pouch ones and the powder packs that are the most widely used. Powder packs are the disposable kind sold everywhere in winter, with or without adhesive. Standard adhesive patches run about 10 by 13 centimeters, and a Daiso listing for six mini patches gives the smaller size as roughly 7 by 10 centimeters.
Adhesive patches go on clothing, never on skin. Korean guidance says to place them over underwear and then add outer layers, so neither the adhesive nor the heat touches bare skin directly.
Pocket packs are the ones you grip in a hand. Wikitree offers a counterintuitive tip, though: rather than holding a pack in your hands, keep it near parts of the body that run warm, such as the abdomen or the inner thighs, because that holds a steadier temperature for longer. For feet, it suggests attaching the pack to the top of the foot instead of the sole.
One rule of thumb follows from all this: use a patch when you will be standing or walking outdoors for hours, and use a pocket pack for a quick hand warm-up between errands. That matches how the sources describe each type, though the sources do not lay it out as a formal rule.
Reusable alternatives exist too. In 2010, the JoongAng Daily described microwave-heated grain pads sold at Lotte Mart for 5,000 to 6,000 won, which the retailer said gave about three hours of warmth after 30 seconds in the microwave. That product was aimed at children, and it shows reusable warmers have been around for a while.
Where to Buy Them and What the Winter Numbers Say
Hot packs are sold at convenience stores and at Daiso, and demand tracks the weather closely. During the first 20 days of January 2026, when Seoul's perceived temperature fell below minus 20 degrees Celsius, hot pack sales rose 42.7 percent year on year at GS25, 30 percent at 7-Eleven and 22.2 percent at CU, according to Aju News.
Those figures cover one cold stretch at one set of stores, so they show demand rising with a deep freeze and say nothing about the whole season. A CU official put the jump down to the sharp drop in perceived temperature and the spreading flu, and GS25 also reported thermal underwear sales up 84.9 percent over the same period.
Price depends on the pack. Daiso's listing for six mini adhesive patches showed 2,000 won, and it stated a peak temperature of 65 degrees Celsius with an average of 55 and a duration of about six hours. Those are the manufacturer's numbers, and the listing showed the item sold out at the time of writing, so check what is on the shelf when you arrive.
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| When the cold arrives, hot packs move to the front of the winter shelf. |
How a Bag of Iron Powder Makes Heat
A disposable hot pack makes heat by letting iron rust quickly. According to a POSCO newsroom explainer, the bag contains iron powder, carbon powder, salt and water, and iron gives off about 1.69 kilocalories of heat per gram as it oxidizes in contact with air.
Carbon and salt act as accelerators, and the heat settles at roughly 40 to 60 degrees Celsius for around three to four hours. North American disposable warmers rely on the same chemistry, so a Korean pack will feel familiar to anyone who has tucked one into a glove.
Air does the activating, which is why Korean guides spend so much time on how to open and shake a pack. Light shaking spreads the iron powder and boosts its contact with oxygen, while the POSCO piece warns against shaking too hard because that can damage the packaging. Wikitree adds that you should let a freshly opened pack sit for a minute or two in open air before slipping it into a pocket, since a thick coat can choke the reaction.
Several more habits come up repeatedly. Open packs one at a time if you carry several, because an opened pack keeps reacting. Choose a recently made pack, according to a December 2023 Financial News report, since older packs may have had more air contact. GQ Korea's guide also notes that some packs start very hot, so wrap them in a cloth or a layer of clothing to temper the first stretch.
Where to Put Them Through the Day
The best spots are the places where blood collects and the places where cold bites first. Wikitree's guide on adhesive packs recommends the lower back, the inner edge of the shoulder blades, the middle of the calf and the lower abdomen.
Its reasoning is that big muscles in the back and waist gather blood, so heat applied there warms the whole body. Calves tend to have slower circulation, so a pack in the middle of the calf warms the leg. Lower abdomen placement makes sense because organs and nerves cluster there, and a chill in that spot spreads quickly through the body.
Stack those placements against an ordinary winter day and a plan appears. Put a patch on the lower back before leaving the house, let a pocket pack handle the walk to the subway, and move the patch to the shoulder blades when the office feels drafty. That guide says to shift a patch periodically instead of leaving it in one place, which doubles as a safety habit. One Wikitree headline even says that delivery riders, who spend whole shifts outdoors, follow the same method.
For feet, the top-of-foot tip from the Wikitree guide is worth remembering, since it says that spot holds a steadier heat than the sole.
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| A pack in one hand, a warm cup on the table: a typical stop on a Seoul winter day. |
The Burn You Do Not Feel
The main risk with hot packs is low-temperature burns, which develop from moderate heat applied for a long time and often do not hurt until the damage is done. Local Naeil reports that skin tissue can begin to be damaged at 44 degrees Celsius after one hour, and at 50 degrees after just three minutes. Burns usually show up after two hours or more of continuous contact.
It also cites Korea Consumer Agency data from 2015 to 2018, with 226 hot pack incidents reported and 87.2 percent of them involving burns. That data is several years old, so treat it as a sign of the pattern rather than a current count.
Advice is consistent across Korean sources. Keep a layer of cloth between the pack and your skin, and limit continuous use to under two hours. Never sleep with a pack on, since you cannot feel the heat building, and people with diabetes, poor circulation or older age, along with children, should avoid packs or take extra care.
If a burn does happen, the guidance is to cool the area under cold running water and then see a doctor. Folk remedies such as potato slices or alcohol are specifically discouraged.
The same report extends the warning to other heat sources. It says to keep at least a meter away from heaters and to set electric blankets to low, around 37 degrees Celsius, since a pack on top of a heated bed stacks one source on another.
Reusing, Storing and Throwing Away
A lukewarm pack may still have life in it. POSCO's explainer and the Financial News report both suggest sealing a still-warm pack in a zip-top bag before it cools completely, because cutting off the oxygen stops the reaction and lets you reuse it later. When a pack seems spent, the Wikitree guide says a brief exposure to open air can restart the remaining iron powder.
Unopened packs keep best in a sealed bag, away from big temperature swings. Used packs go in with general waste, the Financial News report says, in Korea's standard volume-based trash bag instead of the recycling bin. GQ Korea's guide suggests the iron can serve as fertilizer for potted plants, so the sources differ a little, and local waste rules are the safer guide.
If you are headed to Seoul in winter, a few packs from a convenience store or Daiso cost little and weigh almost nothing. Put a patch on your base layer, keep one in the coat pocket, and move them around as the day goes on.
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