EMF is the scale that is used to measure the Electromagnetic Frequency of any electrical appliance. This scale describes how much invisible radiation is being put off by an appliance, such as a computer, cell phone, or in this case, an infrared sauna.
As with any type of radiation, prolonged exposure can pose some health risks. The level of risk is directly tied to how high the EMF is. Thankfully, most infrared saunas have an extremely low EMF. Some have an EMF of zero. If you are looking for the healthiest infrared sauna option, then make sure the one you select has a lower EMF rating.