THE BOATHOUSE LAB / TECHNOLOGY EXPLAINED
Infrared isn't magic. It's physics.
Here's how energy from the heaters can warm the body, why red-light devices are a different question, and where a person's experience ends and a health claim begins.
PART 01 / HEAT
What you're actually feeling.
An infrared sauna uses emitters that release infrared radiation—electromagnetic energy beyond the red end of visible light. When radiation is absorbed by skin, clothing or nearby surfaces, it becomes heat. Your body also exchanges heat with the surrounding air. The amount you feel depends on the emitter, its distance, air temperature, clothing and duration.
Far-infrared sauna heat is mainly a thermal experience. A warm sensation does not require a high air-temperature setting, and a lower setting may be more comfortable for someone who is sensitive to heat. My fully-clothed demo-sauna breaks were about comfort, not a measured infrared dose.
The equipment and its settings determine the spectrum and output.
Energy is absorbed and redistributed; clothing affects direct exposure.
Responses vary with body, environment and exposure; a response is not proof of reduced inflammation.
PART 02 / DIFFERENT WAVELENGTHS
Far infrared, near infrared and red light.
Far infrared
Sauna panels designed primarily to deliver warmth. It is not accurate to assume far-infrared light travels deeply throughout the body unchanged.
Near infrared
May be delivered by dedicated near-infrared LEDs or other emitters. Light–tissue interactions depend on wavelength, output, distance and exposure.
Red light
Visible red-light LEDs are often discussed with photobiomodulation. A claim about a particular red-light device cannot automatically be transferred to a sauna cabin.
Modern mPulse systems can combine multiple technologies, but a model's feature list does not tell us what happened in a historical 2017–2019 session or prove a medical outcome. Read Sunlighten's own explanation of the distinction ↗.
PART 03 / WHAT STUDIES MEASURE
Warmth isn't the same as deep-body heating.
A 2025 controlled comparison of hot-water immersion, traditional saunas and far-infrared saunas in 20 healthy adults found substantially different changes in core temperature and immune responses across the three approaches. The infrared protocol in that study produced less core heating than the others. Those results cannot be generalized to every device, session or patient. Read the research abstract ↗.
We should resist the phrase “penetrates deep into your organs and fixes inflammation.” A product can feel beneficial without such a mechanism being demonstrated.
What does the actual inflammation evidence show? →REAL LIFE / NOT A PRODUCT CLAIM
Why that matters to me.
Even fully dressed in a demo sauna, I remember valuing a few minutes of low, comfortable heat before going back to work. On other days I sat in an mPulse at the Day Spa. I still use a Solo at home when the pain is particularly difficult. That's what I experienced—and it's a good reason to ask better research questions, not to skip them.