A lighting apparatus (10) comprises a light engine (12) producing ultra violet radiation. An enclosure (14) surrounds a radiation generating area of the light engine (12) to encompass the radiation. At least one wall (28) of the enclosure (14) is substantially reflective of the ultraviolet radiation. The enclosure (14) includes a replaceable top portion (30) which includes a phosphor portion (32). The phosphor portion (32) is spaced from the radiation generating area of the light engine (12) by a height of the enclosure (14).