UV can be very useful in the HVAC ductwork to clean the coils and make them more efficient. However, the only air that can be cleaned in the ductwork is the air that actually circulates through it. Given the mechanical limitations of existing ductwork and the energy intensity of moving air through it, one might expect to achieve up to a few additional important equivalent air changes utilizing UV in the ductwork. The advantage of in-room UV like whole room Far UV-C or Upper Room Germicidal UV is that it is cleaning the actual air in the room that you are more likely to breath in and can achieve 20+ equivalent air changes per hour, which is often required to materially limit the transmission of pathogens between people in occupied spaces.