Far infrared saunas utilize the principle of radiant heat.  Radiant Heat transfer radiant energy from an emitting heater to human body directly rather than simply warming the air.

 
MaxSauna far infrared saunas use far infrared energy emitted by high-tech infrared heaters to penetrate the human tissue, muscles and organs up to 3 inches below the skin, and our bodies readily absorb infrared energy as the tuned infrared light waves and the human body vibrate at the same frequency, this process is called resonant absorption, resonant absorption activates the human body at the cellular level, producing a host of physical and chemical changes within the body that are directly responsible for improved health and wellness.