Influence of ventilation system and air flow rate on ammonia levels in pig fattening units

The aim of this study was to determine the influence of air flow rate and ventilation system (under or over-floor extraction) on the evolution of ammonia concentrations both inside the building and in the air discharged into the atmosphere.Animal performance was also measured.In the same time, two air flow rates were compared: (low, starting at 5, gradually increasing to 16 m3/h/pig and high, from 15 to 40 m3/h/pig ).Whatever air flow rate or ventilation system, animal performance was unaffected.Low air flow rate compared with high rate showed an increase in ammonia level in ambient air (37%). In the building, ammonia levels measured by bubbling method are higher (27 %) for the over-floor ventilation system. It was the same for average levels measured by test tube showing less homogeneity when air is extracted over-floor. Calculated ammonia emissions are similar for both ventilation systems (393 vs 349). However, ventilation rate seems to be more important for ammonia discharged into the atmosphere. Increasing air flow rate from 1 to 2.7 results in an increase in ammonia emission by 37 %. Finally, over-floor system with high ventilation rate generated the most important emission.