Concentration of volatile organic compounds within indoor dairy facilities.

Volatile organic compounds (VOCs) are important components of indoor air quality in dairy production systems, yet information on their spatial distribution and dominant compounds within enclosed barns and milking parlors remains limited. This study aimed to characterize VOC profiles and quantify concentrations across indoor locations in commercial dairy facilities operating under different housing and ventilation configurations. Air samples were collected from cow housing barns and milking parlors at two commercial dairies in Weld County, Colorado, including a mechanically tunnel-ventilated barn with a rotary milking parlor (Farm A) and a naturally ventilated barn with an automated milking system (Farm B). Weekly integrated air samples were obtained using evacuated 6-L stainless steel canisters deployed for a 7-day sampling period. Canisters were positioned at three locations within each barn and at the center of each milking parlor, while temperature, relative humidity, and wind speed were recorded simultaneously. A total of 52 VOC species were consistently detected across both dairies. Gas measurements in the barns were averaged by location and ranked by concentration to represent overall conditions. Methane, ethane, and propane were the most abundant compounds in both farms' barns and milking parlors. Hydrocarbons, including n-butane, n-pentane, and i-butane, as well as acetonitrile, were consistently detected but varied in relative ranking across locations. Spatial variability within barns revealed distinct concentration patterns associated with sampling position. These findings provide characterization of VOC composition in indoor dairy environments and highlight the importance of spatial sampling for identifying dominant compounds, which might help to improve air quality.