These earthed sheets are designed to be placed underneath a sheet on a bed, and when earthed, can lower powerfrequency electric fields and drain any charge from your body to ground. It is vitally important to remove any source of mains electricity close to your bed or your electric field exposure will rise. We advise that you should measure the electric fields your body is exposed to when you are lying on the bed - both with and without the sheet being earthed. That will enable you to ensure your electric field exposure is lowered. Please contact <technical(at)emfields-solutions.com> if the electric fields rise when the sheet is Earthed. You can hire the ELF PF4 meter to take the measurements. If used in addition to a canopy, this product is suitable for screening underneath the canopy as the material is also effective at screening RF fields. The canopy and the grounding sheet should be connected together. Body grounding sheets normally cover about a third of the bed as shown in the picture. Most people just want to be earthed, if however you feel you are being zapped from rising pulsed RF fields from below then you might want a large one to cover the whole bed.