Medical equipment such as EEG, EKG and EMG are disturbed by alternating magnetic fields. Thus, for example in hospitals, it must be ensured that the required limit values are not exceeded in areas where such devices are used.

Krankenhaus Nord, Vienna

Krankenhaus Nord, Vienna

Before the start of the construction of Krankenhaus Nord, Vienna, simulations and measurements were carried out to determine the strength of the magnetic fields at the site of the new hospital. This was done in particular because three railway lines and a substation of the Austrian Federal Railways (ÖBB) are located in the immediate vicinity of the hospital. The studies and measurements showed that the values for the operation of medical equipment such as EEG, EKG and EMG according to the ÖVE/ÖNORM E 8007 “Starkstromanlagen in Krankenhäusern und medizinischen genutzten Räumen” are exceeded.

Limit values in the standard ÖVE/ÖNORM E8007

400 nTSS 200nTSS 100 nTSS

Preliminary measurements in selected rooms during the construction phase revealed peak values of magnetic flux density B of 2 μT for external 16.7 Hz magnetic fields and B = 300 nT for 50 Hz magnetic fields.

Thus, it could be assumed that influences on electromedical measuring equipment were to be expected. As a measure to reduce the magnetic fields in those rooms in which intensive medical examinations are planned or where sensitive medical electronic devices are to be used, a shielding, flat encapsulation was provided. In total, more than 60 critical rooms with a shielding area of more than 13,000m2 were affected.

The Systron PowerShield® room shielding system was chosen for the large-area enclosure. This is based on a combination of Mu-metal and aluminium and was described in a study by a technical university as the most suitable system for limiting magnetic fields in hospitals. Systron PowerShield® room shielding system elements are mounted on floors, walls and ceilings. Finally, the sheets are welded together. The mumetal-based system is lightweight, corrosion-resistant, has a high shielding effect and thus meets the high requirements for medically used rooms.

After completion of the shielding work, measurements were carried out in the shielded rooms to prove the effect. The specified shielding factor of 2-5 could be confirmed without any problems.

In total, more than 60 rooms in which EEG, EKG, EMG and other sensitive medical equipment is operated were effectively protected from the low-frequency magnetic fields of the railway using the Systron PowerShield® room shielding system. With these measures, 16.7 Hz fields in particular, but also 50 Hz fields, are reduced to uncritical values.