Red Rock River Resort - Spa Minnekahta - What is Far Infrared (FIR)?

What is Far Infrared (FIR)?

Heat and light waves are part of the larger electromagnetic energy spectrum. According to scientific theory, energy travels in waves and the distance of the wave from crest to crest is called a “wavelength,” (normally measured in “microns” or 1/1,000,000th of a meter). Light visible to the naked eye includes relatively short waves starting at about 0.38 microns (violet) and going to longer waves of about .77 microns (red) with all other colors of visible light in between.

Waves or rays shorter than violet are called “ultraviolet” (UV), while waves or rays longer than red (and therefore lower or “infra” on the electromagnetic spectrum) are called “infrared” (IR). Most of the energy produced by the sun and radiated to the earth is in the IR segment of the electromagnetic spectrum.

Infrared rays (IR) are subdivided into three broad categories, based on wavelength:

	Category	Wavelength
	"Near" or "Close" IR	0.77 to 1.5 microns
	"Mid" or "Medium" IR	1.5 - 5.6 microns
	"Far" or "Long" IR Often referred to simply as FIR (far infrared)	5.6-1,000 microns

Of these three, Far IR or FIR is the only wavelength that can deeply penetrate the human body to provide a number of benefits.

At a core temperature of 98.6°F, the human body emits heat energy at a wavelength of 5-15 microns. A FIR energy wave of similar length is emitted when natural sand or granite is heated. Some studies have shown that FIR energy emitted from stone can penetrate organic matter 80 times deeper than other heat waves.