When selecting air cleaning and disinfection technologies for existing buildings, care and professional judgment should be taken to understand the pros and cons of each technology, as well as their impact on existing building systems. Factors to consider include the type and size of the building, the number of occupants, the type of airborne pathogens present, and the existing HVAC system design and operation. It is also important to consult with experts in the field and follow guidance from reputable organizations, such as ASHRAE.