Skin cancer, other related skin effects and vision impairment which can occur as a result of exposure to optical radiation have been a source of major concern to the world. This work seeks to characterise the optical radiation sources by considering the geometry of the optical radiation source and the detector. The level of risk associated with the optical radiation sources at various distances was found to be increasing with increasing distances for extended sources and decreasing with decreasing distances for point sources. The optical sources investigated appear to be safe in normal operation except for Bilurubin lamp and Dental curing lights. The control measures to reduce the risk associated with these sources were presented. Performance evaluation of USB (hand-held) spectroradiometer was carried out so that it can be used for onsite measurements. This book will be a guide to health workers (who are occupationally exposed to this hazard) as well as professionals in the field of instrumentation. It is equally a source of information to health and safety executives (HSE) or anyone else who may be considering safety issues in relation optical radiation or its instrumentation.