For the development of odour emission model to study odour emission reduction, the chemical and physical properties of roughly 200 different gases that constitute odour from livestock production has to be better known. As for ammonia, the formation process, the diffusion and the transport in and out the livestock facility must be better understood and described. The process can be modeled by floor models, section models and airflow models. The section model is presented as being less known. This model attempt to sum up the diffusion coming from different areas or section of an animal house ( for example in a swine building with slatted floor: wet floor in animal area, back of the wet slatted floor, stored manure under the slats, wet side wall, wet and dirty animals). To be able use prediction ammonia emission models, more measurements have to be done and more knowledge of the emission processes have to be acquired.