This paper presents data from theoretical modeling and actual laboratory measurements of the UVC intensities at the surface of typical HVAC coils. To understand how effectively the UVC penetrated the coil’s interstitial spaces, measurements were taken at the coil’s surface, 1”, 2”, 3” and 4” depths respectively. UVC intensities were measured and recorded with a calibrated radiometer. The radiometer was capable of producing results that are traceable to NIST and through NIST to the International System of Units. Modelings demonstrating expected reduction of typical coil biofilms are presented using varying UVC intensities at the varying coil depths.