In this paper, the magnetic flux density (MFD) distribution in a neonatal intensive care unit is described and MFD values inside a few open infant warming systems and incubators are reported. Typical measured values of the magnetic flux density at power frequency (50 Hz) in the "general environment" (the rooms of the unit) were lower than 0.2 microT, while higher MFD values were detected close to medical equipment and inside the open infant warming systems. In both cases, the magnetic flux density quickly decreases with increasing distance, so that measured values are reduced to "background" (i.e., general environment) levels 20-30 cm away from the sources. The total harmonic content over the 100-800 Hz frequency range was also evaluated. In the general environment, measured values in this band were negligible, while this was not the case close to medical equipment. Field levels inside the open and closed incubators depend on the position of the electronic control system, of the heating power generator and its winding conductor, and of the 220 V main plug. The magnetic flux density was also monitored for a prolonged period of time in a few types of open infant warming systems and incubators under standard intensive care unit operation with premature newborn present.
2004 Wiley-Liss, Inc.