Light and photobiomodulation
Eye safety and light
Eye safety with any light-emitting device is decided by measurement — wavelength, irradiance at the eye, exposure time and geometry — not by appearance. Our answer is design: the user's head sits outside the sauna, away from the direct light, and the lights switch off when the doors open.
Also called eye protection, goggles, blue light hazard, photobiological safety, IEC 62471
What determines it. The framework is IEC 62471, Photobiological safety of lamps and lamp systems, which assigns a lamp to a risk group from Exempt to Risk Group 3 on measured radiance and irradiance against several separate hazards — including the retinal blue light hazard (roughly 400–500 nm) and the retinal thermal hazard, which extends into the infrared. ICNIRP publishes parallel guidance covering LEDs. Assignment requires measurement of the actual product.
The two wavelength-specific points.
- Blue. Short-wavelength visible light carries the greatest photochemical retinal hazard per unit energy. The concern is intense sources at close range.
- Near infrared. 850 nm is invisible, so it does not trigger the blink reflex, the aversion response or pupil constriction that limit exposure to bright visible light. The eye’s own protection does not operate, which is why infrared sources are assessed against a separate retinal thermal limit.
How the Red Light sauna addresses it. By keeping the eyes out of the light rather than by putting a filter in front of them. Every emitter is mounted inside the sauna. The user’s head stays outside it throughout the session, above the neck opening and away from the direct line of the emitters, and the lights switch off as soon as the doors are opened, so the array is never running while someone is looking into the sauna. That is why goggles are not needed for a sauna session.
Do not look directly into any light emitter at close range, in any device.
Why it matters here
If you run sessions for other people, this is a question you will be asked. The answer for the Red Light sauna is design rather than eyewear: the head stays outside, and the lights switch off the moment the doors open.