A conventional sauna must rely only on indirect means of heat: first, on convection (air currents) and then, conduction (direct contact of hot air with the skin) to produce its heating effect on us. In a far infrared sauna, less than 20% of the infrared energy heats the air, leaving over 80% available to be directly converted to heat within our bodies. Thus an infrared sauna can warm its user to a much greater depth and much more efficiently than a conventional sauna. This crucial difference explains many of the unprecedented health benefits reported to be available through a far infrared sauna that are not attainable through a conventional sauna.
The infrared energy applied in these saunas may induce up to 2 - 3 times the sweat volume of a hot-air sauna. They operate at a significantly cooler air temperature range of 110° to 130°F vs. 180° to 235°F in a conventional sauna. The lower heat range is safer for those concerned about cardiovascular risk factors that might be encountered in old-style hot-air sauna
The electromagnetic spectrum is divided into three segments by wavelength, measured in microns or micrometers(a micron = 1/1,000,000 of a meter) : 0.076 to 1.5 microns = near or close; 1.5 to 5.6 = middle or intermediate; 5.6 to 1,000 = far or long wave infrared. The far infrared segment of the electromagnetic spectrum occurs just below, or "infra" to red light as the next lowest energy band. This band of light is not visible to human eyes but we can, however, feel this type of light, which we perceive as heat.When warmed, the earth radiates infrared rays in the 7 to 14 micron bands with its peak output at 10 microns. Our palms emit infrared energy at between 8 to 14 microns. The Soft Heat® sauna heaters emit the majority of their output in the long band from 5.6 to 25 microns. The output is evenly spread around the 9.4 micron pivot point of peak human output. The energy output from the infrared sauna corresponds so closely to the body's radiant energy that our bodies absorb close to 93% of the infrared waves that reach our skin.