The use of litter and manure in welfare-oriented systems for laying hens may negatively affect the air quality and the work environment. The objective of the current case study was to compare concentrations of ammonia, dust and bacteria in 3 such systems: 1) a floor housing system, 2) a multilevel system, and 3) a system with furnished cages. Data was collected from 3 houses of each type, and 1 house of each type was selected for detailed measurements for 1-2 weeks. Daily average concentrations of ammonia were 3-12 ppm in the house with furnished cages, 21-42 ppm in the multilevel system, and 66-120 ppm in the floor housing system. Total dust concentration was 2.0- 2.5 mg x m^-3 in the house with furnished cages, 0.71-2.4 mg x m^-3 in the multilevel system, and 6.8-18 mg x m^-3 in the floor housing system. The number of bacteria cells per m³ was .1-2.2 x 10⁷ in the house with furnished cages, 2.2-3.4 x 10⁷ in the multilevel system, and 8.0-9.6 x 10⁷ in the floor housing system. In the system with furnished cages, concentrations of ammonia and dust were of the same magnitude or below concentrations found to reduce pulmonary function in poultry workers in other studies. Concentrations of ammonia in the multilevel system and concentrations of both ammonia and dust in the floor housing system were above these levels.