Dust and odour relationships in broiler house air

Abstract

The hypothesis that odour concentration is related to dust in broiler house air was tested experimentally in terms of particle numbers, dust mass and dust surface area. A small-scale representation of a broiler house was constructed and exhaust air from it was blown through a filtration unit containing coarse and fine fabric filters and an electrostatic precipitator. Samples were taken of raw and filtered air and analysed by particle counting and dynamic dilution olfactometry. Samples for odour measurement were introduced to the olfactometer both directly and via bags made from “Tedlar” film. Dust mass and surface area were calculated by integrating the particle numbers with respect to particle diameters. Measurements of dust and odour were also made in a commercial broiler house. There was no significant change in odour concentration caused by dust filtration, but dust mass and surface area were significantly reduced. There was no correlation between odour concentration and dust mass or surface area. Total particle numbers changed little with filtration, but there was considerable change in particle size distribution as larger particles were filtered out. The dust content of air was significantly reduced in all respects after the air had been put into “Tedlar” odour sampling bags and subsequently sub-sampled, although odour concentration was not significantly affected. A simple model, based on Stoke's Law, and the experimental use of an aluminium foil bag showed that electrostatic precipitation occurred rather than purely sedimentation. Dust measurements in a commercial broiler house showed that the particle size distribution was similar to that in the raw air of the experimental house although the actual concentration was higher. The use of a 1 m long sampling tube could apparently halve the measured dust concentration indicating a need for sampling tubes to be as short as possible and of the same dimensions to ensure comparability. An airstream helmet reduced the dust concentration by 96%.