Area UV disinfection units have proliferated as of late due to their effectiveness and ease of use in decontaminating hospital rooms and surfaces of nosocomial pathogens of HAIs (Hospital Acquired Infections). However, the levels of UV irradiance and UV dose produced can vary widely from unit to unit. It is routinely assumed that the lower irradiance levels produced by some of these area disinfection units can be compensated for by increasing the time length of the exposure, a principle that is known as reciprocity. Reciprocity, however, may not apply to very short exposure times or to very low levels of irradiance due to the fact that some microorganisms can resist and cope with low UV doses and even recover via repair mechanisms (IUVA 2005). Herein we examine the effects of UV dosages produced by typical area disinfection units including the IPT™ whole room UV light disinfection systems.