The UV chamber simulates the effect of UV with fluorescent ultraviolet (UV) lamps, while rain is simulated by the condensation of humidity. In the solar spectrum UV light represents roughly 5% of the sunlight but it is responsible for most of the polymer degradation. Also, materials are often tested with equipment, which simulate only the shortest wavelengths (UV).

The UV-B range includes the shortest wavelengths found in sunlight. Therefore, for many applications, it is a fast and efficient method. A UV test uses two main types of lamps: UVA-340 and UVB-313.

As shown in Figures 1, while these lamps have different light emission spectrum, they are both characterized by a maximum of emission in the UV range. UVA provides a reasonable match of the UV region of the solar spectrum, but this match is no longer valid for the longer wavelengths (visible, IR).UVB lamps also emit UV light, but the maximum of the emission spectrum is shifted towards short wavelengths compared to the UVA lamps. The UVB-313 lamp is a widely used type of fluorescent UV lamp that provides fast test results. However, as shown in Figure 1, the spectrum contains short wavelengths, which are not present in the solar radiation.