The goal of RP-1705 was to develop a new understanding of the airside fouling of air-cooled condenser heat exchangers and to develop a method to realistically mimic fouling in a laboratory. Past research on airside fouling has mostly focused on evaporators, or has used reduced airflow in laboratory tests as a proxy for condenser fouling in experimental work to study the effects of fouling on system performance. The current project’s approach was to study the airside fouling effects on field-fouled condensers, by removing them from the field and testing them in the laboratory. A second objective in this work was to build on the new knowledge of actual field fouling to develop a laboratory method to test the effect of fouling on new condensers.