T he methods of management used in poultry production today require that the personnel work during several hours of the day in an atmosphere with high levels of air contaminants such as gases, organic dust, airborne microorganisms, and toxins. Poor air quality in poultry houses is a common environmental condition, and several respiratory diseases have been reported, including allergies connected with work in poultry houses (Danuser et al., 1988; Leistikow et al., 1989; Brown, 1990). Strong evidence exists to suggest that there are health risks also to workers in poultry slaughter houses (Olenchock et al., 1982; Hagmar et al., 1990). The air quality in poultry buildings also has an impact on animal health, with damages to the respiratory system of the exposed animals (Feddes et al., 1997; Van W icklen et al., 1997). Several studies of the environment in poultry buildings have reported high concentrations of air contaminants, such as gases, e.g., ammonia and carbon dioxide, dust, airborne microorganisms, and L. M årtensson, C. Pehrson Abstract New rearing systems for laying hens must be developed as the result of animal welfare legislation in Sweden that will ban the use of cages. The up-breeding of layer-type pullets must also take place in systems similar to those used in egg production units. In this study, the air quality and the climatic conditions in a multiple tier rearing system were compared with conditions in a battery system. The studies were run simultaneously with layer-type pullets from one day old to 16 weeks of age. The gases measured were ammonia and carbon dioxide and the particulate matter was measured as total dust, respirable dust, endotoxin, and airborne microorganisms. The results indicate significantly higher levels of total dust and endotoxin in the multiple tier rearing system than in the battery system. This was most obvious at the end of the rearing period. Airborne microorganisms were found in considerable concentrations in both systems. W hen animals were unloaded, personal sampling gave elevated levels of dust that exceeded the Swedish hygienic threshold value. This may be related to a raised activity of the animals and to the close contact between the workers and the animals. Keyw ords. Working environment, Animal buildings, Dust, Ammonia, Endotoxin, Air pollution, Poultry. Journal of Agricult ural Safet y and Healt h 3(4):217-228 © 1997 ASAE 1074-7583 / 97 / 0304-217 217 Air Quality in a Multiple Tier Rearing System for LayerType Pullets The authors are Lennart Mårtensson, PhD, Division of Work Science and Technology, Department of Agricultural Biosystems and Technology, Swedish University of Agricultural Sciences, Alnarp, Sweden, and Division of Working Environment, Lund Institute of Technology, Lund University, Lund, Sweden; and Christina Pehrson, Medical Laboratory Technician, Department of Medical Microbiology, Lund University, Lund, Sweden. Corresponding author: Lennart Mårtensson, Division of Work Science and Technology, Department of Agricultural Biosystems and Technology, Swedish University of Agricultural Sciences, PO Box 88, S-230 53 Alnarp, Sweden; tel: +46 40 41 5490; fax: +46 40 41 5489; e-mail: <lennart.martensson@jbt.slu.se>.