As a result of the 2015 unprecedented high pathogenic avian influenza outbreak in the United States, some egg producers in the US started to use inlet air filtration to reduce the risk of disease transmission into hen houses through air route. Removal efficiency of particulate matter (PM), the carrier of airborne pathogens, by such filtration systems has not been investigated. This field study was, therefore, conducted to evaluate the PM removal efficacy by an electrostatic air filtration system (consisting of a low-grade air filter and an electrostatic particle ionization or EPI system) installed at the inlet of a commercial high-rise hen house. Evaluation was performed in two test rounds over one-year period. Results show that average PM removal efficiencies in rounds 1 (spring to summer) and 2 (late fall to spring) were respectively 66% and 29% for PM₁, 66% and 30% for PM_2.5, 66% and 31% for PM₄, 68% and 36% for PM₁₀, and 68% and 45% for total PM. Removal efficiency became unstable when the EPI system was inactivated (i.e. when solely relying on the filter for PM removal). House static pressure and ventilation rate indicated considerable clogging of the filter media by dust accumulation and the need for replacement after ~16 weeks of use in spring-to-summer time (round 1); however clogging was not an issue during the entire late fall-to-spring sampling period (round 2, 24 weeks). Appearance of the filter changed gradually as dust accumulated with time, which can be captured by image analysis and used to judge filter dirtiness and lifespan. Findings of this field study provide insight into the efficacy of PM removal by such a low-cost air filtration system, which will help egg producers in their decision-making for disease prevention strategies.