Electromagnetic Radiation found in a typical building today is an integral part of technology evolution. Electric power distribution networks are present in every building producing time variable magnetic and electric fields in a low frequency range (50 Hz - 100 KHz) commonly named as Extremely Low Frequencies (ELF). On the other hand wireless networks and other high frequency activity, in the range of Radio Frequencies (RF) 100 KHz up to 6 GHz produce ElectroMagnetic Fields (EMF) that radiate in the indoor environment. In this work the potential to take advantage of such electromagnetic pollution to provide power supply to micro-devices (such as wireless sensors) is examined. This is based in real EMF measurements in a typical office environment.