|Modern mobile devices may be used for many different purposes. There are differences between the ways of using them depending on the service. Also, the exposure to RF-EMF is different depending on the service, environment and the conditions of the use of the mobile devices. This Supplement describes the various factors that determine the level of RF-EMF exposure, as defined by the specific absorption rate (SAR) that is induced in the users of mobile and portable radiocommunication devices. Based on this technical information practical information and guidance is provided for users of mobile devices.