Five bales were randomly chosen from a stack of 6-month-old barn-stored hay. Four 2·5-kg sections were taken from each bale and subjected to one of four different water wetting treatments, 0-min soak, 10-min soak, 30-min soak and 80-min steaming. Post wetting, the sections were shaken for 9 min under a Negretti LS45F personal dust sampler which sucked-in any particles released into the surrounding air. The sampler contents were then analysed for respirable particle numbers (particles < 5um), and the hay subsampled and analysed for water-soluable carbohydrate, N, Na, K, Ca, P, Mg, Zn, Mn, Fe and Cu. The steaming and soaking treatments all proportionately reduced respirable particle numbers by more than 0·93 of those present in the dry hay. Soaking for 10 min and 30 min significantly reduced levels of P, K, Mg, Na and Cu, whereas the steamed samples showed no loss of nutrients from the levels present in the dry hay. Thus in terms of reducing respirable particle numbers and conserving nutrient levels, steaming for 80 min is the most effective treatment when preparing hay fodder for horses.