Figure 2. Cross-section of a water-filtered infrared-A radiator (Hydrosun, Müllheim, Germany) .

The whole incoherent non-polarized broadband radiation of a 3000 Kelvin halogen bulb is passed through a cuvette containing water, which absorbs or decreases the undesired wavelengths within the infrared region (most parts of infrared-B and -C and the absorption bands of water within infrared-A). The water is hermetically sealed within the cuvette. A fan provides air cooling of the cuvette to prevent the water from boiling. (from [1])