ABSTRACT

Ultraviolet (UV) light has been used as a bactericidal agent from as early as 1928 (Miller et al., 1999). UV light is a portion of the electromagnetic spectrum ranging from 100 to 400 nm wavelength and has the potential to induce damage to the deoxyribonucleic acid (DNA) by forming thymine-thymine dimers (Bank et  al., 1990; Miller et  al., 1999). These dimers prevent microorganisms from transcription and replication, which leads to cell death (Miller et al., 1999). UV light can be applied in two modes, namely, continuous UV light mode (conventional one) and pulsed UV (PUV) light mode. PUV light provides higher instantaneous energy intensities than continuous UV light and hence is more effective in inactivating microorganisms. PUV light is produced by accumulating the energy in a capacitor and releasing it as a short-duration pulse (in the order of microseconds) to magnify the power greatly by xenon lamps (Xenon, 2003). These ash lamps radiate a broadband emission light (approximately between 100 and 1100 nm) with a considerable amount of light in the UV spectrum (<400 nm).