EMI Meter's measures the relative amount of dirty electricity, or electromagnetic interference (EMI), on wiring in buildings. It measures the amount of EMI in millivolts (mV). The amount of EMI correlates to the amount of sound emitted by the EMI meter which also relates to the amount of EMF on the wiring. The Power Perfect Box Plug-In acts as an EMI filter and reduces the amount of EMI. Using the EMI Meter to measure before and after plugging in a Power Perfect Box Plug-In will demonstrate how it can reduce the amount of EMI and related EMF radiation.