An ultraviolet radiation lamp comprising a heat absorbing element on the exterior thereof such that, during operation of the lamp, the temperature of the lamp in contact with the heat absorbing element is at a lower temperature than the remainder of the lamp. The use of the lamp in a radiation source module and a fluid treatment system is also described. The ultraviolet radiation lamp is particularly useful for treatment of fluids such ambient air (e.g., containing pollutants), warm liquids and the like.