What is far infrared? CIE IR-A/B/C bands

JPHEAT editors (Kawaguchi Seiken Co., Ltd.) / Updated 2026-11-15

Invisible light with a long wavelength.

Light is named by its wavelength. Light with a longer wavelength than visible light is infrared, and the eye cannot see it. The CIE defines infrared radiation as roughly 780 nm (0.78 μm) to 1 mm. [1]

The bands depend on the standard.

The CIE divides infrared into IR-A (0.78–1.4 μm), IR-B (1.4–3 μm) and IR-C (3 μm–1 mm). [1]

The boundaries of “near, mid and far infrared”, however, differ by field and use. The BOKEN Quality Evaluation Institute, a Japanese textile testing body, describes 3–1,000 μm as far infrared. [3] When you see the term, check which standard it follows.

Everything with a temperature gives off infrared.

Objects give off infrared according to their temperature. The hotter they are, the shorter the peak wavelength; the cooler, the longer (Wien’s displacement law). For objects near room or body temperature the peak lies at about 9–10 μm, in the far-infrared region.

Radiation thermometers and thermal cameras capture this infrared and convert it to a surface temperature. [10]

Heat travels three ways.

Heat travels by conduction, convection and radiation: conduction between things in contact, convection through moving air or water, and radiation as infrared and other light, without passing through the air. [2]

The warm surface of a heater, a floor or a pad also radiates. Products used in contact with the body or the mattress also pass heat by conduction.

Absorbed, it becomes heat.

When infrared is absorbed, its energy turns into heat. ICNIRP explains that long-wavelength infrared (IR-C) is absorbed in the layers near the surface. [5] This is a general physical explanation and says nothing about what any product does to the human body.

Far infrared in daily life and industry.

Far infrared is nothing special. It has long been used for heating, such as floor heating and far-infrared heaters, for drying coatings and food, and in charcoal and oven cooking. [6][7][8][9] Radiation thermometers and thermal cameras, the infrared images of the Himawari weather satellites (the 10.4 μm band and others) and the AKARI infrared astronomy satellite (50–180 μm) all capture infrared. [10][11][12]

What can and cannot be said.

What can be said with certainty about far infrared are physical facts: how it is classified by wavelength, that it carries heat by radiation, and that it turns into heat when absorbed.

The wavelength bands do not tell you what it does to the human body. “Near field” is a different idea, about distances between objects, and does not mean “near infrared”. [4] Nor can a wavelength figure alone tell you how warm something feels: that depends on temperature, the amount of radiation, contact and the conditions of use.

About JPHEAT’s measured data.

JPHEAT had a third-party testing body measure the relative radiation spectrum and normal total emissivity of a test sample of the JPT100J heated mattress pad (Single). Among the recorded points, the relative intensity peaked at about 8.35 μm (in the CIE IR-C band), and the normal total emissivity was 0.89.

Both are results for the JPT100J test sample under the test conditions. They are not values for other models or for every setting, and they are not measurements of any action on the human body.

Questions and answers

What is far infrared?

The name for the long-wavelength part of invisible infrared. In the CIE bands it corresponds roughly to IR-C (3 μm–1 mm), and BOKEN describes 3–1,000 μm as far infrared. The boundaries differ by field and use.

How do near, mid and far infrared differ?

They are classified by wavelength, but the boundaries differ by field and use. The CIE uses the bands IR-A, IR-B and IR-C. When you see “near, mid, far”, check which standard defines them.

Does far infrared glow red?

No. Far infrared cannot be seen. Heaters that glow red are giving off visible light as well as infrared.

How does far infrared carry heat?

By radiation, which travels without needing moving air, and it turns into heat when absorbed. Heat also travels by conduction and convection.

Are “near field” and “near infrared” the same?

No. “Near infrared” is a name for a wavelength range; “near field” is an idea about distances between objects. Research on thermal radiation studies what happens across very small gaps.

Does the wavelength tell you how warm it is?

A wavelength figure alone cannot tell you how warm something feels. Temperature, the amount of radiation, contact and the conditions of use all play a part.

Sources

The public sources explain general physical principles and terms only. They do not mean that these institutions recommend JPHEAT products, and they say nothing about any action on the human body.

Based on JPHEAT product specifications and manuals, and on public sources.

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What far infrared is: wavelength and how heat travels.