The purpose of this study was to develop reference test dusts and test procedures for experimental evaluation of heat exchangers in dusty environments and analyze the impact of particulate fouling on the performance of four heat exchangers in both heating and cooling modes. Reference test dusts were chosen among several types of commercially available powders for experimental evaluation of air-side particulate fouling performance of fin-and-tube heat exchangers with respect to particle size distributions, density, and material cost. Four heat exchangers ofvarying fin densities and shapes were experimentally tested in both heating and cooling modes with Masons Hydrated Limestone powder with a particle mass median diameter (MMD) of 14.5 μm and a low cost organic test dust with a much larger particle mass median diameter (MMD=1067 μm, respectively. The experimental results showed that the impact of air-side particulate fouling on the performance of a heat exchanger is mainly attributed to increased airflow resistance, while the resulting increase in thermal resistance played a less significant role. When a heat exchanger was used to heat air in an environment with aerosolized limestone powder, the airflow resistance across the heat exchanger would increase gradually, on the order of 2.1% to 6.7%) from the initial state in a four-hour intensive test. During this time, the thermal conductivity of the fin surfaces would degrade only slightly. However, when the organic test dust was used, the heat exchangers would clog quickly and the airflow resistance would double in 11.4 to 76.8 minutes while the airflow was held constant. Heat exchangers with higher fin densities clogged much more quickly and led to a faster rate of pressure drop increase. When the heat exchangers were used in a cooling mode the presence of condensation created a dust/water slurry that deposited inside the cooling coils, causing the airflow resistance to increase more rapidly. With the organic test dust in these cooling tests, the airflow resistance doubled within 7.6 to 21.6 minutes of operation, which is 50% to 260% faster than their corresponding heating cases. When cooling coils were exposed to aerosolized limestone powder, the airflow resistance increased at rates comparable to the cases with the organic test dust. In our experiments, the reduction of heat exchanger performance due to particulate fouling was primarily observed as an increased air-side flow resistance, while increased resistance to heat transfer by an insulating particulate deposition layer on fin surfaces played a lesser role in performance degradation.