Infrared full-spectrum sauna (IR-A, IR-B and IR-C) – physics, tissue penetration and biological mechanisms
Infrared sauna is a technology that uses electromagnetic radiation in the infrared range to transfer energy to biological tissue. Unlike traditional saunas, which primarily heat the air, infrared systems transfer energy directly to the body. An infrared full-spectrum sauna combines several parts of the infrared spectrum and therefore differs from simpler solutions that use only one type of infrared radiation.
What is meant by an infrared full-spectrum sauna
The term full spectrum refers to the use of several infrared wavelength ranges at the same time, usually IR-A, IR-B and IR-C. These ranges have different physical properties and different tissue penetration. A full-spectrum sauna is designed to cover a broader spectral range and thereby provide more varied energy transfer than saunas that use only far-infrared light.
The infrared spectrum: IR-A, IR-B and IR-C
Infrared radiation is usually divided into three main ranges. IR-A is closest to visible light and has wavelengths of approximately 700 to 1400 nm. IR-B is in the range of approx. 1400 to 3000 nm, while IR-C covers the range from around 3000 nm and above. These ranges have different absorption patterns in biological tissue, mainly determined by water content, blood and tissue structure.
IR-A has the deepest tissue penetration and can reach several centimeters into the tissue. IR-B has more limited penetration and is absorbed to a greater extent at the surface. IR-C is absorbed almost completely in the upper layers of the skin and primarily contributes to surface heating.
Tissue penetration and heat transfer
One of the most important differences between the infrared ranges is how the energy is absorbed in the body. IR-A can penetrate relatively deeply and contribute to the heating of deeper tissue. IR-B provides a combination of surface and intermediate-depth heating, while IR-C mainly provides rapid heating of the skin surface. In a full-spectrum sauna, these ranges work together and create both local and more deep-reaching heat exposure.
Heat transfer takes place mainly through direct absorption of infrared energy in the tissue, as opposed to convective heating via hot air. This provides a different physiological experience than in traditional saunas.
Biological responses to infrared heat
When biological tissue absorbs infrared energy, the temperature increases locally. This can affect circulation, tissue elasticity, and metabolic processes. The heat may lead to increased blood flow in the skin and underlying tissue, as well as activation of the body's temperature-regulating mechanisms. These responses are general physiological reactions to heat and are not specific to a single wavelength.
In full-spectrum systems, different infrared components are combined to create a more varied thermal stimulus, where both superficial and deeper tissue are exposed to heat energy.
Sunlighten mPulse smart infrared sauna – front and glass door
The difference between traditional infrared saunas and full-spectrum
Many infrared saunas use only IR-C, often referred to as far-infrared light. This provides effective surface heating, but limited tissue penetration. A full-spectrum infrared sauna also includes IR-A and IR-B, which provides broader spectral coverage and a different distribution of heat in the tissue. This is a technical difference in how the energy is delivered, not just in how warm it feels.
Use and practical considerations
The use of a full-spectrum infrared sauna involves exposure to heat over a given period of time. Temperature, exposure time, and individual tolerance vary. Modern systems are designed with a focus on controlled heat output, safety, and comfort, and are supplied with the manufacturer's recommendations for use.
Conclusion
A full-spectrum infrared sauna represents a technological approach in which multiple parts of the infrared spectrum are combined to provide broader and more varied heat transfer to biological tissue. By using IR-A, IR-B, and IR-C simultaneously, both superficial and deeper tissue layers can be exposed to infrared energy. This distinguishes full-spectrum saunas from simpler infrared solutions and provides a different biophysical basis for heat exposure.
About Uno Vita's editorial team
This article has been prepared by Uno Vita's editorial team and is based on available scientific literature, technical documentation from manufacturers, and Uno Vita's experience with infrared, light, and electromagnetic technologies. The content is intended as general professional information and should not be understood as medical advice, diagnosis, or treatment. Uno Vita AS works with integrative and technology-based solutions in areas including photobiomodulation, infrared technology, hydrogen and oxygen systems, PEMF, and frequency-based systems. In the event of health concerns or medical questions, it is always recommended to contact qualified healthcare personnel. Freedom of expression and the professional communication of biophysical principles are central to Uno Vita's informational work.
Scientific references
Vatansever F, Hamblin MR. Far infrared radiation (FIR): Its biological effects and medical applications. Photonics Lasers Med. 2012.
Yaroslavsky AN et al. Optical properties of human skin and subcutaneous tissues. J Biomed Opt. 2002.
Hershler C. Infrared and thermal physiology. J Appl Physiol. 1991.
Boulant JA. Role of the preoptic-anterior hypothalamus in thermoregulation. J Appl Physiol. 2000.
Schneider M et al. Infrared radiation and tissue heating mechanisms. Phys Med Biol. 2019.
