For nearly a century, ultraviolet germicidal technology has been effectively used to destroy surface and airborne microbes such as tuberculosis, measles, and more. But for reasons that are difficult to pinpoint, its applications have mostly been limited to such high-risk locations as emergency rooms and surgical suites. That changed in the months following the COVID-19 outbreak. Suddenly a variety of facilities from churches to hair salons were looking for ways to safely return to normal. Not surprisingly, their search led many to ultraviolet germicidal irradiation (UVGI), and specifically to upper-room (UVGI), as a way to mitigate the risk of infection. This paper will explain in a manner that is accessible to all building owners and managers what upper-room UVGI is, how upper-room UVGI differs from other UV strategies, and what makes it a particularly relevant solution for a wide range of mainstream applications today.