[Edited version of a poster presentation by Y.F. Shen, colleagues and faculty, Department of Veterinary Preventative Medicine, The Ohio State University, at the 2024 annual conference of the American Association of Swine Veterinarians]

Poor indoor air quality with high levels of airborne particles and residual gases such as ammonia (NH₃) and hydrogen sulfide (H₂S) could be a source of respiratory challenges in swine housed in commercial farms. Negative air ionization systems (NAIS) have been shown to be effective in reducing airborne particles in human indoor environments, but research is limited for swine-specific farm conditions. The objective of this study was to evaluate NAIS as a technology to reduce airborne particulate matter and gaseous pollutants at two different height levels (2 feet and 5 feet: pig and human respiration levels, respectively), under field conditions.

Negative air ionization systems were installed in six farrowing rooms in a 5,000-sow herd. Two treatment groups were assigned: 1) NAIS installed with lamps ON (L-ON), 2) NAIS installed with lamps OFF (L-OFF). Treatment was assigned at the room/batch level for three weeks, following the site’s all-in all-out system; all rooms were cleaned and disinfected between batches.

Particulate matter (PM, 2.5 and 10) and gaseous pollutant (NH₃, H₂S, carbon monoxide) measurements were taken in each room at 2- and 5-foot heights twice a day (morning and evening), two fixed times per week, using commercially available and scientifically validated monitoring systems. Daily changes in particle counts (morning and afternoon) and gas concentrations were analyzed. During the time of analysis, three replicates of each treatment were completed for a total of 92 time points.

Results showed numerically greater reductions for PM in the L-ON group compared to the L-OFF group, except in PM 10 at 5 feet. Greater reductions were observed at the 2-foot level compared to the 5-foot level in the L-ON group. The study found that L-ON successfully kept NH₃ levels below 3 ppm at the different heights during the entire study. (Figure 1). This is important because recent research indicates that maintaining NH₃ levels below 10 ppm can reduce health risks for both pigs and humans.

Hydrogen sulfide was reduced in the L-ON group at both the 2- and 5-foot levels. It was not detected in the L-OFF group. Carbon monoxide was not detected throughout the study in any of the rooms.

NAIS appears to be effective in decreasing airborne particles and residual gases for both swine and production workers. NAIS shows potential as a practical solution for producers in real-world field conditions.