What is the mobile phone SAR used for?

The SAR or Specific Absorption Rate is a measurement that allows you to evaluate the maximum transmitting power of the microwave waves from a mobile phone to a biological organism. Its value is expressed in Watts per Kilogram and the measurement protocol is defined by the CENELEC (Comité européen de normalisation électrotechnique).

Each mobile telephone is also tested before its release on a phantom (a fake human head filled with a specific liquid) so that local SAR measurements can be taken (head and ears, the zones that would be most exposed) with the SAR value of each phone being obligatorily noted in the user manual. In Europe, it can not pass over 2 Watts/Kg, while in the United States it is set to 1.6 Watts/Kg.

These values are the maximum amounts authorised, although the effect of radio frequencies are also being studied for their thermal effect (the heating of tissue) which cuts in from 4 Watts/Kg. Numerous studies suggest that the biological effects appear well before this, leading to some scientists and organisations requesting that only low levels be authorised.
 
As a general rule, mobile phones currently have a SAR of between 0.5 and 1.5 Watt/kg. These values represent a maximum, with their emission power being a lot lower of the conditions allow for it (good network coverage, no obstacles…). The emission power of a mobile is adapted depending on each of these different parameters.
 
While the SAR value isn’t always easy to find, it can be used as a criteria when choosing a new phone. For more details about radio frequencies, see out article.