Far infra red sauna is somewhat different than traditional sauna. It emitts a wavelength known as far infra red. This wavelength is capable of bringing about a more efficient and more effective means of detoxification.
This type of sauna doesn't get near as hot as traditional saunas so it is much more comforatable. 120 degrees compared with 160 to 180 degrees. Even at this lower temperature it induces more sweating. Also based on studies it pulls more toxins out with the sweat. Traditional saunas cause a portion of toxins to be circulated back to the liver putting an extra burdon on it.
This effect is proven to be much less with far infra red.
Also of note. When physicists measured the wavelenght of energy emitted from healers hands they found it was far infra red energy. Not all far infra red emitters are equal. There is an optimum frequency within the far infra red spectrum and some, not all, emitters hit this sweet spot. I know of some emitters from Ireland that emitt in this sweet spot. These saunas are expensive but you can make them for under 500 dollars yourself. That's what I did. Mine may not be as pretty as proffesional models but it was 10 times cheaper and just as effective. Function vs. form. If you can't be bothered to make your own there are several good ones around. I could recomend a couple if you are interested.