The determination of air change rate in naturally ventilated cattle barns.

The keeping of animals in livestock buildings requires the ventilation of these buildings. On the one hand good climatic conditions for the animals in the livestock building have to be provided, on the other hand the emissions have to be kept at a low level. The airflow through the livestock building plays an important role for both opposing requirements. The targeted control of the climate in the livestock building and for the minimization of emissions calls for knowledge about airflow and emission streams. Especially for naturally ventilated buildings, the determination of air change rates leads to a few problems. For those cases, the Institute of Agricultural Engineering Bornim has developed a 40- sampling-points system which is using Krypton 85 as a tracer gas. All 40 sampling points are running simultaneously with a maximum sampling rate of one second. Air change rates of up to 1000 h-1 have been measured. During the past 2 years more than 20 naturally ventilated cattle barns have been investigated. Apart from the measurement of volume flow, the concentration of gases and odours has been measured as well. In parallel to these inside investigations inside the barns, the climatic conditions outside have also been recorded. The results are extensive data on emissions. The measured emission flows of odours can be used - among other things - to calculate the minimum distance between livestock buildings and human living areas.