Influence of measurement method, measurement height, and sampling location on carbon dioxide and ammonia concentration in a conventional piglet nursery.

Low air quality and the presence of harmful gases such as ammonia can have detrimental effects on the health and welfare of pigs. Excessive concentrations of these gases are particularly common in negative pressure ventilated barns found in conventional husbandry systems. There are various devices and guidelines available for measuring harmful gases in such environments. In this study, ammonia and carbon dioxide were measured using three different devices. Measurements were taken across four production cycles in six pens at two different heights (0.6 m, within test pens; 1.5 m, representing human working height). The measurement results for ammonia and carbon dioxide obtained with the three different methods differed significantly from one another. Comparison of the two measurement heights revealed no significant difference for ammonia. However, measurement height had a significant effect on carbon dioxide concentrations. Furthermore, the location of the sampling points (test pens) within the compartment significantly influenced the measured concentrations of both ammonia and carbon dioxide, indicating spatial variability. When assessing air quality in a barn, it is advisable to use two different measurement systems for ammonia and carbon dioxide to ensure reliable results. Measuring ammonia does not necessarily have to be performed at animal height, as its vertical distribution was found to be uniform within the compartment. However, the location of the sampling points significantly influenced both ammonia and carbon dioxide concentrations. Therefore, measurements should be conducted at multiple locations within a compartment to capture spatial variability and to determine the most appropriate position for stationary sensors.