Opening the sealed packaging lets oxygen react with the bag. Within a minute they release constant heat. Typically these packs are used for comfort, increasingly however, they are used in rescue operations where a survivor is trapped in a cold or exposed place.
Opening the sealed packaging lets oxygen react with the bag. Within a minute they release constant heat. Typically these packs are used for comfort, increasingly however, they are used in rescue operations where a survivor is trapped in a cold or exposed place.