Body warmers are suitable in crisis situations where you know that you will be forced to spend time in adverse weather conditions.You can just as well provide the warmer to a person who has suffered an injury or is in shock, and an external heat source will help the body not get into hypothermic shock. They are suitable for skiers, tourists, soldiers, fishermen, etc.
After opening the vacuum-sealed package, a chemical reaction with fresh air enters, releasing heat in the range of 50° - 65° Celsius for about 20 hours.