The national zoning model of emission security is used, among other things, for the assessment of buildings and properties with stationary CI processing devices with regard to their emission properties.

In the zoning model of emission security, buildings are divided into zones based on their attenuation properties for electromagnetic radiation, and devices with emission properties matching the respective zone are divided into classes. Both aspects belong inseparably together: both the location of a CI processing device and the emission properties of the device itself have a decisive impact on the level of achievable security against compromise through emissions. Based on this, the focus for risk minimisation is always on maintaining a maximum achievable reception level (from the point of view of an attacker) at the perimeter boundary.

Figure 1 shows the zoning model schematically; the distances refer to the equivalent free-space attenuation up to the boundary of the controlled area that the property or the building or part of the building has.

Equivalent free-space attenuation means: attenuation due to level drop over the named distance in free space or attenuation due to the surroundings (e.g. building or cabin), which reduce the level just as much. It is important to note that only metallic components provide efficient shielding, e.g. a close-meshed steel mesh. In contrast, masonry, glass, concrete, stone, plaster, wood or the like in a wall thickness do not represent a significant obstacle to electromagnetic emissions. The Technical Guideline BSI TR-03209 contains more detailed information in this regard.