Far infrared is radiant heat that heats objects directly without heating the air around. The electromagnetic spectrum is divided into three segments by wavelengths. 0.076 to 1.5 microns is close/near infrared, 1.5 to 5.6 is center infrared and 5.6 to 1000 is far-infrared. This band of light is not visible to the human eye but can be seen with special cameras. Humans absorb this light as heat. A far-infrared sauna will radiate far-infrared heat through ceramic heaters, while the room is a comfortable temperature, the body will warm because, as stated above, far infrared heats the object not the air. Our Infra-Core far-infrared sauna use ceramic emitters that are 96% radiant efficient. The ceramic emitters allow the user to absorb the majority of the heat making it a 93% far-infrared intake. Having the far-infrared emitters radiate at a compatible micron level as the human body, allows for optimum far-infrared penetration.