Extremely low frequency magnetic fields have been classified as “possibly carcinogenic to humans” by the World Health Organisation. More research needs to be done to establish a causal link. However, if you’re concerned about potential long-term health effects of exposure to low frequency electric and magnetic fields, this meter will help you easily detect them. You can then take remedial action in your home if needed.
Low frequency fields can come from a wide range of sources. Here are a few examples:
If you think these fields could be affecting you, or you simply want to reduce your exposure, the Wiring Home Meter - PF Meter can help. It enables you to quickly identify the source and intensity of the field(s), so that you can take action to reduce your exposure. For example, if a high field is detected near to your favourite chair, you may wish to consider moving it to a lower-exposure area.
An electrical field is present in all live wires, whether or not the appliance is in use. Magnetic fields are only there when an appliance is in operation .
The Wiring Home Meter - PF Meter will detect electric and magnetic fields at low frequencies (between 20Hz and over 50 KHz)
If you are looking to measure radio-frequency fields, for example from Wi-Fi and smartphones, you might prefer meters that measure higher frequencies like this one.
The meter has a line of LED lights that show the levels of either Electric Fields between 5 and 200 V/M and Magnetic Fields between 0.02 and 2.0 ut. The meter also gives a sound signal to show how strong the fields are. With a ‘Geiger-counter effect’, the sound increases with the strength of the field. This makes it easy for even beginners to interpret the results given by this meter. You can turn the sound off if you prefer.
 Source: http://www.arpansa.gov.au/radiationprotection/factsheets/is_magfields.cfm