Your questions about the electromagnetic fields observatory

General Questions

The EMF Observatory has been created in 2020 to measure and observe the evolution of people’s exposure to electromagnetic fields and to make the results accessible to everyone.

Exem is a laboratory specialized in the inspection of people’s exposure to electromagnetic fields and has developed connected sensor technology in order to offer this innovative electromagnetic supervision service.

Cities wishing to do so can join the EMF Observatory on their own initiative. The Exem company then offers a complete service which goes from the deployment of sensors on street furniture to the restitution of the results on www.observatoiredesondes.com.

The deployment plan is defined for each city according to the sites of technical interest (presence of radioelectric antennas), demographic (nurseries, schools, universities, etc.) or symbolic (tourist sites or high traffic areas). Exem brings its expertise and experience to optimize the choice of locations for measurement sensors.

The sensors measure the electrical component of the field emitted by radio communication systems. For example, for the most known emissions, the mobile telephony, the FM broadcasting, the digital terrestrial television or even the wifi.

About electromagnetic fields

A wave is a physical phenomenon that transports energy without moving matter. The simplest example to represent a wave is that of a pebble thrown on the surface of a puddle of water thus creating a disturbance on its surface. This disturbance is the result of the energy transmitted by the thrown pebble but does not cause the water to move. Only the energy propagates by creating wavelets which attenuate in the medium of propagation, the water.

Another well-known wave makes it possible to apprehend this phenomenon. It is the acoustic wave which, in the same way, propagates in the air while attenuating with the distance from the source.

The electromagnetic wave is the combination of an electric field and a magnetic field capable of propagating in different media such as air (on the surface of the earth) or even vacuum (in space). The electromagnetic wave is characterized by its amplitude (intensity of the wave) and its frequency, which gives it particular physical properties. 

At very low frequency, the electromagnetic wave is for example very suitable for transporting electrical energy but becomes a formidable means of transporting information at higher frequencies. We then speak of radio frequencies which are used in mobile telephony or for the broadcasting of radio and television.

The volt per meter is the unit of measurement for the electric field that is measured during exposure control. Indeed the magnetic component of the field expressed in ampere per meter (A/m) can be directly calculated from the electric field. It is therefore not necessary to measure it during an inspection.

To find out more about electromagnetic fields, do not hesitate to consult the sites  http://www.radiofrequences.gouv.fr or to visit our website https://exem.fr.

Measurement system

In France, the decree 2002-775 defines the limits of public exposure to electromagnetic fields. These limits vary according to the frequency of the waves measured and are based on the recommendation of ICNIRP, in accordance with the opinion of the scientific steering committee of June 25-26, 1998. On the frequency band measured by the sensors of the observatory, the limit varies between 28 V/m and 61 V/m. By viewing sensor tracking graphs, you can view the most restrictive 28 V/m limit.

In France, the ANFR/DR protocol is the reference for carrying out regulatory checks. A free surveillance system allowing checks to be carried out in residential areas and establishments open to the public has been set up by the Decree 2013-1162 of December 14, 2013. These inspections are carried out by societies accredited by the COFRAC, of ​​which EXEM is a member (accreditation 1-5014, scope available on www.cofrac.fr ) and carried out punctually by authorized technicians when a request is made. The EMF Observatory is a complementary device to the regulatory measures bringing more transparency by allowing the follow-up in real time via a platform for the general public. 

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