Three nursery trials were conducted to determine effects on room air quality and pig performance of adding 5% soyabean oil to starter diets. Settled dust was reduced 45-47% by adding oil. Total bacterial colony counts increased over time but were 27% lower for pigs fed the oil diet. Pigs fed the oil additive showed a 3.6% higher feed conversion efficiency. Ammonia (0.7-4 ppm) and CO2 (500-2500 ppm) concentrations varied somewhat between trials, but were not influenced by the addition of oil.