What Is Far-Infrared (FIR)?
A Light We Borrowed From the Sun
Think of sunlight through a window on a cold winter day — the air is still cold, yet your face feels warm. That's infrared: a kind of light you can't see but can feel directly. In 1800, the British astronomer William Herschel passed sunlight through a prism and found a region just beyond red light that was invisible, yet still warmed a thermometer. He named it 'infrared' — literally, beyond red.
The Three Regions of the Infrared Spectrum
Infrared isn't a single, uniform kind of light — it splits into three regions by wavelength, each with its own uses and its own way of interacting with the body:
Near-Infrared (IR-A)
- The shortest wavelength, closest to visible red light. Used in remote controls and infrared cameras.
Mid-Infrared (IR-B)
- Common in thermal imaging and some industrial heating applications.
Far-Infrared (IR-C)
- The longest wavelength (around 10,000 nm). It sits closest to the wavelength the human body itself radiates — which is exactly why it feels like the most comfortable, natural form of heat. Sunlike Tec panels operate precisely in this band.
Why Far-Infrared, Specifically?
Far-infrared is considered the spectrum's safe, comfortable region — it's exactly why it's used in saunas, therapeutic heating devices, and increasingly in homes. It should never be confused with ultraviolet (UV) light, which sits at the opposite end of the electromagnetic spectrum entirely — physically, the two have almost nothing in common. In the next section, we look at that difference in more detail, and at exactly how far-infrared heats a room.