This study aims to assess the levels of extremely low frequency magnetic fields (ELF-MF) emitted from portable hand-held fans (HHFs) and their principal frequency and to identify factors influencing these levels. We collected a total of eleven models of HHF and monitored the ELF-MF as a function of fan speed and distance from the fan. EMDEX II was used to monitor the ELF-MF. An SMP2 EMF-meter equipped with a P400 field probe was used to determine the levels of ELF-MF and the frequency spectrum. Ten of the fans, excluding only one bladeless-fan model, emitted a high level of ELF-MF near the source of the HHF direct-current motor. The maximum measured level of ELF-MF ranged from 14.07 to 218.7 µT. All measurements of the ELF-MF taken within 10 cm from the HHFs showed values higher than 1.0 µT. ELF-MF levels were found to decrease markedly with distance, regardless of the HHF product. The level of ELF-MF rose noticeably with increased fan speed. The speed of and distance from the HHF significantly influenced the level of ELF-MF. All principal frequencies ranged from 1 to 300 Hz, which falls in the typical range of ELF. Bioelectromagnetics. 2019;40:569-577. © 2019 Bioelectromagnetics Society.

中文翻译：

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便携式手持风扇发出的极低频磁场的强度表征。

这项研究旨在评估便携式手持风扇（HHF）发出的极低频磁场（ELF-MF）的水平及其主要频率，并确定影响这些水平的因素。我们总共收集了11种HHF模型，并根据风扇速度和与风扇的距离对ELF-MF进行了监控。EMDEX II用于监视ELF-MF。使用配备有P400现场探头的SMP2 EMF仪来确定ELF-MF的电平和频谱。除仅一种无叶风扇型号外，十个风扇在HHF直流电动机的电源附近发出了高水平的ELF-MF。ELF-MF的最大测量水平范围为14.07至218.7 µT。在距HHF 10 cm范围内进行的所有ELF-MF测量值均高于1.0 µT。发现ELF-MF水平随距离而显着降低，而与HHF产物无关。ELF-MF的水平随着风扇速度的提高而明显上升。HHF的速度和与HHF的距离显着影响ELF-MF的水平。所有主要频率的范围为1到300 Hz，这属于ELF的典型范围。生物电磁学。2019; 40：569-577。©2019生物电磁学会。