A traditional sauna heats air to 150 to 195 degrees; an infrared sauna runs cooler but warms the body directly. This episode explains full spectrum light and thermal dose: spectrum, intensity, distance, time and enclosure. Go to https://creatrixsolutions.com/products/sauna-thermal-dose for more information.
Step into a traditional sauna and the thermometer on the wall might read 180 degrees Fahrenheit. Step into an infrared sauna and it might read 130. So the traditional sauna is hotter, right? Not quite. Comparing the two by air temperature compares the wrong number, and this episode explains why.
A traditional sauna heats the air with a stove and stones, sometimes with steam, and the hot air heats you. An infrared sauna sends radiant energy straight to the skin, so the body warms before the air does. The thermometer reports the air. It says nothing about how much radiant energy is reaching the person on the bench.
The better questions are these. What spectrum is the heat source producing? How intense is that energy where you sit? How far are you from it? How long is the session? And how well does the enclosure hold what the lamps deliver? Together, those describe the thermal dose of a session.
Start with spectrum, because the phrase full spectrum gets used loosely. Infrared is divided into near, mid and far bands. Near infrared runs from about 700 to 1,400 nanometers, mid from 1,400 to 3,000, and far above 3,000. Those are approximate labels, not biological dividing lines. An incandescent tungsten filament does not switch on at one wavelength. It emits a broad, continuous spectrum that begins around 550 nanometers, in visible amber light, and runs through visible red into near, mid and longer infrared at the same time. An LED produces one or two narrow bands. A far infrared panel emits mainly at the long end. So the honest question about any full spectrum sauna is not the label on the box. It is the measured output of the heat source.
Red light interacts mainly with the skin and the tissue just beneath it. Near infrared generally travels farther before it is absorbed, though how far depends on wavelength, tissue, pigmentation and dose. Chung and colleagues, in a 2012 review, describe roughly 600 to 1,070 nanometers as the window where light passes through tissue most readily, which is why that range dominates photobiomodulation research.
Now distance, and this is where thermal dose really separates from temperature. Radiant intensity falls fast as you move away from the source. One bulb manufacturer's broadband measurements show the curve: about 1,431 milliwatts per square centimeter at 4 inches, 671 at 8 inches, 268 at 12 inches and 101 at 16 inches. Those figures are total output across visible and infrared wavelengths, heat included, not a therapeutic dose. Sauna Fix users normally sit 18 to 30 inches from the bulbs, farther still. Two saunas with the same bulbs can deliver very different exposures depending on where you sit and how long you stay.
Then the enclosure. Once energy leaves the lamp it can reach you directly, reflect off the walls, soak into the wall material, warm the air, or escape through seams. The enclosure decides which. Insulation slows heat loss, and a reflective, low-emissivity lining sends radiant energy back into the occupied space instead of absorbing it. Reflection also preserves wavelength: a reflected near infrared photon is still near infrared. The Sauna Fix radiant tent is rated at R-15 insulation with a lining rated to reflect up to 97 percent of incident radiant energy. A single four-bulb lamp brings it to about 140 to 145 degrees. A double lamp with eight bulbs reaches about 185. Same bulbs, different dose.
So how do infrared and traditional saunas compare by dose? A traditional session relies on high air temperature, so sessions tend to be short. An infrared session uses lower air temperature and adds radiant energy from the heat source. And within infrared, exposures still differ. Far infrared panel cabins surround the body with large heating surfaces at greater distances. Incandescent lamp systems place a concentrated source much closer. Reed and colleagues, in a 2025 study in the Journal of Applied Physiology, measured far infrared heating in the human forearm and reported an effective thermal penetration of about 2.4 centimeters, with deeper tissue warming by conduction inward from the skin. Infrared sauna is not one standardized exposure.
What does the research report? Studies measure body and skin temperature, heart rate, sweating and circulation-related markers under controlled heat. Hussain and Cohen, in a 2018 systematic review, summarized those responses across traditional and infrared sauna studies and noted how widely the protocols vary. Imamura and colleagues, in 2001, reported flow-mediated dilation measurements before and after a two-week infrared protocol at 140 degrees in a small group of adults with coronary risk factors. These are reports on specific protocols, not a promise about any sauna. Research describing one heater and enclosure cannot tell you the dose delivered by a different one. Nothing here is a prescription, and sauna use is not intended to diagnose, treat, cure or prevent any disease.
A few practical notes. More heat is not automatically better. Hydrate, start with shorter sessions at a lower setting, and let comfort decide how far to go. Stop at dizziness, nausea, unusual weakness or real discomfort. Anyone who is pregnant, or who takes medication affecting hydration, circulation or heat tolerance, should talk with a healthcare professional first.
Above all, do not judge an infrared sauna by the cabin thermometer. Look at the spectrum of the heat source, the radiant intensity where you sit, your distance from the bulbs, the session length and how the enclosure holds heat. That is the difference between measuring room temperature and thinking in terms of thermal dose. The full guide, with the measurements and the sources, is on the Full Spectrum Light, Heat and Thermal Dose page at creatrixsolutions.com, from Creatrix Solutions, maker of the Sauna Fix near infrared sauna. Creatrix Solutions City: Kennewick Address: 214 E Albany Avenue Website: https://creatrixsolutions.com Phone: +1-866-686-5605 Email: contact@creatrixsolutions.com