Light and photobiomodulation
Near infrared 850 nm
Near infrared at 850 nanometres is invisible light just beyond red. It penetrates further than visible light — several millimetres, depending on tissue and skin tone — and reaches deeper than red light.
Also called NIR, 850 nm, IR-A, near-infrared light
Where it sits. 850 nm is IR-A on the standard classification, the shortest and shallowest infrared band. It is far shorter in wavelength than the 12,000 nm far infrared used for radiant heating in the Standard and Deluxe saunas, and it behaves differently: 850 nm is a photobiomodulation wavelength absorbed by cytochrome c oxidase, while 12,000 nm is absorbed by water at the skin surface and felt as heat.
Invisible, and why that matters. You cannot see it, so you cannot judge its intensity by eye, and it does not trigger the blink reflex or pupil constriction that protect the retina from bright visible light. In the Red Light sauna that is handled by design rather than eyewear: the user’s head stays outside, above the neck opening and away from the direct line of the emitters, and the lights switch off when the doors are opened. See Eye safety and light.
What is fitted. 380+ LEDs at 850 nm, arranged as a full-body-length strip inside the sauna.
The research. Our near infrared studies page collects reviews and trials and links on to the sources, which carry the full citations.
Why it matters here
380+ of the Red Light sauna's 750+ LEDs run at 850 nm. It is invisible, so there is nothing to see while it is running.