How does an infrared sauna work?

Firstly how does an infrared sauna work?
Infrared light, or far infrared as it can often be called, is a wavelength of light naturally emitted by the sun. But whereas some wavelengths of light are visible, infared, or far infrared, is not. An example of the visible wavelengths from the sun is the light that you see when you see a rainbow. This is the visible wavelengths broken into their individual wavelengths for you to see. But you cannot see infared.
Infrared is thermal radiation, meaning that it carries heat. The most common demonstation of this is one that everyone will recognise. You know how, when the sun comes out from behind the clouds there is an immediate sensation of heat on the skin? This is the warming effect of the infrared radiation from the suns light spectrum.
A radiator or electric heater emits infrared light and therefore thermal radiation and this is what causes the heating effect. Or you may even have an infrared heater in your bathroom right now.
Infra red radiation does not heat the air as some forms of heat do, and penetrates the body extremely well, producing heating effects in the body below the skin.
Use of infrared light as a therapy is not new. For many years the healthcare industry used heatlamps utilising infra red technology, but these lamps were difficult to use and became hot to the touch, and were difficult to keep at a constant temparature. Now it is more common to use ceramic infrared heaters where far infrared heating is required. And ceramic heaters are used in modern infrared saunas.
Strangely, as infrared heaters do not rely on the air being hot to work it is quite possible for one to work outdoors or with the door open, except that the user may well feel cold on the skin.
So what is the difference between this and traditional saunas? Traditional saunas are usually known as Finnish saunas, or rock saunas. These use various types of heaters to produce heat to heat up rocks inside the sauna. Very traditional types can produce heat from the burning of wood.
Rocks are heat stable and so keep the heat inside the suana more stable too. The heat, sometimes up to or even over 200 degrees, causes the body to sweat. The humidity is usually increased by throwing water on the stones to “improve” the sweating effect, and this can be uncomfortable. In a very traditional sauna the skin is even flaggelated with birch twigs to increase the effect.
So the bottom line is that an infrared sauna heats the body by direct application of far infrared light rays, whereas traditional Finnish saunas heat the body with hot air.