Measurements are Very Sensitive to Test Conditions
Fortunately, you as a consumer benefit from being able to compare measurements taken by a single company, Vitatech Electromagnetics. They have provided all of the test reports used in the sauna industry. This means the measurements on everyone's reports were taken with the same equipment. It also means you can see in the reports the physical location of where the measurements were taken relative to the heater's surface. Unfortunately, Vitatech Electromagnetics only takes the measurements requested by the sauna companies and only measures in the locations specified by the sauna companies -- there are no standards for these things. This leaves open plenty of room for sauna companies to misrepresent their products.
Measurements taken on different equipment can vary quite a bit. These measurements can be very dependent on distance from the source of the fields, and different equipment will position the sensors in their devices in different locations. Different equipment also have different levels of accuracy and resolution. If you want to duplicate professional measurements, you need the same professional equipment. There are many "ghost hunting" EMF meters you can buy on Amazon, but they will not allow you to duplicate a professional measurement. Further more, there really isn't any consumer-level equipment for measuring electric fields and expertise is needed to take valid electric field measurements.
Electromagnetic fields are like light. They decrease with distance from their source and they stop entirely when power is turned off. There is no standard for where to take measurements in a sauna. The location of the highest levels of exposure is typically at the backrest because this is the closest point to the back heaters, which is where the most power is being used.
For the purpose of comparing saunas, it is recommended to look at independent measurements taken at the backrest, and at the surface of the heaters. Anywhere else gets very difficult to compare between saunas.
Measurements Taken By High Tech Health
High Tech Health uses professional equipment for measuring electric and magnetic fields, however we do not use the exact same equipment that is used by Vitatech Electromagnetics.
For electric field measurement, we use the Gigahertz Solutions ME3951A.
For magnetic field measurement, we use the Enertech Emdex Snap. It is a three-axis meter and quite sensitive.
A Note About Naming Types of Heaters
Panel Heaters: They are also called carbon heaters, or "Combination Carbon/Ceramic Heaters", and sometimes include "full spectrum" heaters. These are any of the heaters that cover a large flat rectangular area on the walls of the interior of a sauna. They are too big to put a reflector behind them to keep all of the heater's output inside the cabin.
"Low EMF" Carbon-style Heaters: This refers to any of the panel heaters that companies call "Low EMF". They have a lower average magnetic field, but despite the marketing materials, also have high maximum magnetic fields, and very high electric fields.
The "Low EMF" Heater Measurements
We took these measurements on a sauna heater produced in the factory that makes saunas for a company currently licensing a hot-tub brand name.