Kairo are portable heat packs. Until the beginning of the 20th century, most people kept themselves warm with an onjaku, a stone heated in a brazier then wrapped in cloth and worn around the stomach, or by burning coal dust in a special container. Later, benzine kairo were invented, which generate heat from a catalytic reaction of vaporized benzine and platinum.
Disposable kairo, commonly used even today, went on sale for the first time in 1975. Heat is generated by the rapid oxidization of iron powder with water and salt. The temperature and duration of the heat generated is controlled by how the materials are blended together. Some disposable kairo can even be stuck on clothing with an adhesive surface. Disposable kairo start heating up once opened, so they’re great for outdoor use.
Microwaveable kairo, a type of kairo that contains a gel-type heat insulating material, can be used after being heated in the microwave. They are great for relieving tiredness in your neck or shoulders and also for warming your toes in winter. Rechargeable kairo (battery-operated) that have built-in or dry-cell batteries and “ecology” kairo, that retain their heat for an hour after the metal inside is stimulated, can be used over and over again, reducing waste.
Disposable kairo are sold at convenience stores, supermarkets and drugstores. Microwaveable kairo and rechargeable kairo are sold at electronic retail stores and department stores. You can also find kairo and kairo covers with Kawaii (cute) designs.
Kairo can be used in so many different situations! Once you try them, you won’t be able to live without them. As they’re reasonably priced, they’re great not only for your winter travels but also as a souvenir.