Introduction

Ultraviolet germicidal irradiation (UVGI) is defined as the use of ultraviolet (UV) wavelengths of light in the germicidal range (200–320 nm) for the disinfection of air and surfaces. The term ‘UVGI’ was originally coined by the International Commission on Illumination (CIE) and adopted later by the Centers for Disease Control (CDC), and this term distinguishes disinfection applications from the non-germicidal UVA wavelengths of black lights and suntan lamps (320–400 nm). UVGI is also used to distinguish air and surface disinfection applications from those in water (CIE 2003). Throughout this book the terms ‘UVGI’ and ‘UV’ will be used interchangeably, with the understanding that in every context, unless otherwise noted, both terms refer to the germicidal wavelengths of UVC (200–280 nm) and UVB (280–320 nm). UV radiation below 320 nm is actinic, which means it causes photochemical reactions. UVA radiation (320–400 nm) is not considered germicidal and is not specifically addressed in this book (except in relation to pulsed light).