The second dataset was collected in a LAE fattening pig facility between January 28th, 2001 and September 18th, 2001 during two consecutive fattening periods (Fig. 1C & D). During the measurements, 144 fattening pigs were present in the pig unit. The dataset consisted of 5338 hourly outgoing NH3 concentrations (mg m−3) and ventilation rates (m3 h−1). No information on the incoming NH3 concentrations (background level) was present, but it can be reasonably assumed that the ingoing air did not contain ammonia.