Two levels of limits
ORNI distinguishes exposure limit values, derived from ICNIRP and aimed at acute health protection, from installation limit values, which apply precautionarily to individual installations.
For 50 Hz installations the installation limit value is 1 µT, evaluated at places of sensitive use in the operating mode that produces the highest field.
Places of sensitive use
These include rooms in buildings where people regularly spend extended periods: apartments, offices, schools, hospitals, and also designated but not yet built plots of land.
Technical rooms, corridors, garages and storage areas are generally not places of sensitive use, which frequently opens practical design freedom.
The approval path
A compliance dossier is submitted with the building or installation permit. It must document sources, currents, geometry and the resulting predicted field at all relevant points.
Cantonal authorities review the dossier, and verification measurements are typically required after commissioning. Planning compliance early is far cheaper than retrofitting shielding into a finished building.